CE Chapter 1, 2 - Construction Engineering PDF

BFC 21002 CONSTRUCTION ENGINEERING 1 PURPOSE To determine the site’s suitability for building and the nature and the extent of preliminary work that will be needed Why it is important? It will shows the detailed to many physical aspect such as subsoil comp...

BFC 21002 CONSTRUCTION ENGINEERING 1 PURPOSE To determine the site’s suitability for building and the nature and the extent of preliminary work that will be needed Why it is important? It will shows the detailed to many physical aspect such as subsoil composition, demolition and the legal aspect such as planning permission, right of access and preservation order 2  PRESERVATION ORDER a legal obligation laid on an owner to preserve a building of historic interest, or to conserve trees and natural habitat regarded as contributing amenity value to the environment. OBJECTIVES To assess the general suitability of the site with the proposed works To help produce a design which is adequate and economic To help overcome possible difficulties & delays that may arise during construction period due to ground and other local conditions To predict possible changes that may occur/cause of all changes in site condition To maximize potential of the site 4 DESCRIPTION A combination process which ranges from looking at published information such as maps to arrange laboratory testing on the soil 5  Information required from a site investigation: a. Information affecting the design of the structure: shear strength and compressibility of the soil b. Information affecting the construction works: the extent and properties of material to be excavated, or to be used for fill or for road bases or as concrete aggregates c. Information on ground conditions: the level and seasonal variation of the water table, the pressure in the soil and the permeability of the soil 6 INFORMATION/ISSUES TO CHECK 1. Site Location  Nearest town and city  Schools, emergency services, entertainment, recreation, shops, transport and employment  Distance from head office (client & builders) & traveling time  Distance from nearest railway station to the site 7 INFORMATION/ISSUES TO CHECK 2. Accessibility mobilization  Approach and site access roads, width, gradient, bends, sharp corners, condition and construction relative to transport heavy plant and equipment machine  Bridges, strength, width and clearance height steel plate  Temporary roads, rolled metal tracts or consider preparing sub base for new crusher run roads as temporary access 8 INFORMATION/ISSUES TO CHECK 3. Availability of space  Site offices, canteen, stores and compound  Material storage areas and handling  Construction area and assembly areas  Plant location concrete mix plant 9 INFORMATION/ISSUES TO CHECK 4. Services electrical supply, water supply, food, transport hostel, security, internet, telco  Water, drainage, electricity, gas & telephone  Location will be determined from maps by consultation with the appropriate local authorities  An estimate of buildings usage is also for ascertaining the demand on sewers and drains 10 INFORMATION/ISSUES TO CHECK 5. Ground composition Boreholes are required to determine :  Changes in strata layer of soils  Strength of subsoil N value  Toxicity of subsoil  Stability of excavation avoid soils from collapse  Water table (depth below surfaces) 11  STRATA Strata are layers of rock, or sometimes soil. In nature, strata come in many layers. It is a term in sedimentary and historical geology; the singular is stratum.... These layers are laid down as sediment, often in the sea, and are slowly changed by pressure, heat and chemical action into rocks. INFORMATION/ISSUES TO CHECK 6. Site clearance and demolition A plan of the site should indicate trees, shrubs and existing buildings and a site survey will reveal the extent of necessary leveling Demolition and excavation  Method and cost  Effect of trees and structural prevention orders 14 INFORMATION/ISSUES TO CHECK  Reuse of materials  Protection of adjacent building  Special insurance requirement  Compensation payment and liability for damage  Distance to spoil tips and charge 15  SPOIL TIPS A spoil tip (also called a spoil bank, boney pile, gob pile, bing, batch, boney dump or pit heap is a pile built of accumulated spoil IN GENERAL… Dealt with local planning authority to ascertain whether there are special/significant restrictions which could adversely affect the development of site building line position Survey should include details of neighboring development, future development and the position with regard to facilities in the area Should enquire the existence of any restrictive covenants such as right of way, light & drainage which may restrict the development 17  THE PROCESS 1. Desk Study 2. Site Reconnaissance/ Walk over survey 3. Preliminary report or feasibility study 4. Preliminary Ground Investigation - Planning of main Preliminary report 5. Main Ground Investigation 6. Laboratory testing 7. Financial Report (Return of Investment) 8. Final report 18 Planning an investigation In the earlier stages of a site investigation, the available information is often inadequate to allow a detailed plan to be made. The investigation must therefore proceed in 3 stages: Desk Study Site Reconnaissance Detail Examination of Tests and Programs DESK STUDIES It is important to collect all available information about the site before starting work. A desk study is the collation and review of information already available about a site, and is carried out at an early stage of site appraisal to inform and guide the remainder of the site investigation. 20 DESK STUDIES Collect as much material as possible about the site such as-  Maps (geological, ordinance survey, etc)  Air photograph  Geological books & journal  Mining records & reports of previous site investigation  Library, news paper, adjacent buildings, etc. 21 DESK STUDIES 22 SITE RECONNAISSANCE / WALK OVER SURVEY  The initial document search should be followed by a walk-over survey of the site and its surroundings.  This should be a methodical examination of the site, based on defined classes of information, which complements the desk study and typically provides valuable information on matters such as:  Topography: indications of slope instability, spoil heaps or signs of ground subsidence resulting from mining. 23  SPOIL HEAP A heap formed of spoil (material discarded during mining or excavation). The place where spoil is dumped. China Clay spoil heap near St Austell, Cornwall.  SITE RECONNAISSANCE / WALK OVER SURVEY  Geology: exposures of soils and rocks which can be examined and sampled.  Surface water and ground water: signs of flooding; springs; water logging  Vegetation: signs of vegetation die-back or restricted vegetation as a result of contamination of the ground; presence of invasive species such as Japanese Knotweed; trees which may cause shrinkage and swelling of clay soils. 25 Japanese Knotweed  SITE RECONNAISSANCE / WALK OVER SURVEY Fallopia japonica, commonly known as Asian knotweed or Japanese knotweed The invasive root system and strong growth can damage foundations, buildings, flood defences, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channels in flood defenses to carry water 27  SITE RECONNAISSANCE / WALK OVER SURVEY  Ecology: indicators of protected species, newts, badgers, bats, nesting birds.  Contamination: indications of spills, disturbed ground, areas of fill or spoil heaps, old fuel or oil tanks.  Structures: settlement of existing structures or the use of asbestos; indicators of archaeological/historical value. 28 Newts & badger  SITE RECONNAISSANCE / WALK OVER SURVEY  Local Knowledge: anecdotal information on past uses of the site or past problems in the area.  Access & services: information such as access for site equipment and location of buried or overhead services 30  TESTS AND PROGRAMS/ DETAILED EXPLORATION The principal objectives of the detailed soil test/investigation are as follows: a. To determine in detail the geological structure of the site, including the thickness, sequence and extent of the strata. b. To determine the ground water conditions 31  TESTS AND PROGRAMS/ DETAILED EXPLORATION c. To obtain disturbed and undisturbed samples for identification and laboratory testing d. To carry out tests to determine the mechanical properties of the soil insitu 32 TESTS AND PROGRAMS/ DETAILED EXPLORATION There are two principal methods of investigating the ground conditions, trial pits and boreholes 33  GROUND INVESTIGATION Trial Pits Trial pits are shallow excavations going down to a depth less than 6m. The trial pit is used extensively at the surface for block sampling and detection of services prior to borehole excavation. Can be dug by hand or mechanical excavator 34  GROUND INVESTIGATION Trial Pits Suitable only in dry area as they allow hand cut samples to be taken which minimize the disturbance of sample Most suitable when exploring back filled area and sites overlain by variable natural deposits 35 GROUND INVESTIGATION 36 GROUND INVESTIGATION Boreholes A borehole is used to determine the nature of the ground (usually more than 6m depth) in a qualitative manner Recover undisturbed samples for quantitative examination.Where this is not possible, for in gravelly soils below the water table, in-situ testing methods are used. 37  GROUND INVESTIGATION Boreholes Obviously the information gained from a borehole is an extremely limited picture of the subsurface structure. It is therefore essential to compare the results obtained with those from the desk study. The greater the number of boreholes the b e t t e r correlation thus more trustworthy results. The two principal types of boring machines used for Site Investigation are light percussive and drilling machines. 38 LIGHT PERCUSSIVE 39 DRILLING MACHINES CHAPTER 1 SUBSTRUCTURE 1.1 Earthwork INTRODUCTION Earthwork: the processes whereby the surface of the earth is excavated and transported to and compacted at another location. Earthworks are engineering works created through the moving or processing of parts of the earth's surface involving quantities of soil or unformed rock. The earth may be moved to another location and formed into a desired shape for a purpose. Much of earthworks involves machine excavation and fill or backfill. Scale: ranges from small works (the excavation of ditches and trenches for drainage and pits and trenches for foundations) to the large earthworks (highways and dams). INTRODUCTION carried out at an early stage in a construction project. completion of the earthworks within the scheduled time is often the key to the completion on time of the whole project success often depends on: o an adequate site investigation and preparing practical and satisfactory designs of the earthworks. o the choice and efficient use of the correct types and size of plant to meet the particular requirements of the site. o Weather condition SCOPE OF EARTHWORKS Site clearing Parameters to be checked on before commencing the clearing works; ❑ marking of the respective area to be cleared and grubbed ❑ checked the cut-off elevations ❑ checked depth and size of trees to be removed ❑ identified clearly and verified the existing utilities and services lines ❑ ensure that monuments, markers and special trees are properly marked for protection. ❑ marks all trees and vegetations that are to be undisturbed ❑ potential hazard such as flammable area, slipping area, etc. ❑ terrain, soil condition and foliage ❑ ensure that sub contractor has proper controls of erosion and drainage ❑ environment protection plan has been approved and the contractor is familiar with the requirements Site clearing Site Clearing Involves; ❑demolition of existing buildings, ❑the grubbing out bushes and trees, ❑disposal works and ❑the removal of top soil to reduce level. Clearing, grubbing, demolishing, breaking up and removing all trees, shrubs, vegetation, butts, structures such as walls, fences and other obstruction within the site which have been designated to be demolished or removed. All spoils and debris shall be removed and disposed of off- site at an approved certified construction landfill. Site clearing Transport and moving Earthwork transportation is something that projects seldom avoid. Earthwork is expressed in units of volumes (cubic meters in metric). Increases in such volumes require additional trucks (or more runs of the same truck), which cost money. It is important for designers to design the project which require very little earthwork. Trucks or dump trucks are the most necessary equipment to transport excavated material, aggregates and construction material.  Transport and moving Transport and moving Compaction Reasons: Increased bearing capacity Increased compressibility Reduce permeability Improve stability Heavy/highway vs. building foundation compaction operations Compaction  All pronounced depressions left in the original ground surface by removal of objectionable material from within embankment limits are filled with acceptable material and compacted to the density required.  The upper 6 in. of the original ground is compacted weighing no less than 10 t, or with other approval compacting equipment. Compaction  Compacting equipment requirements vary from contract to contract.  The types of compactors commonly used are: ❑ Three wheel roller ❑Smooth drum vibrator roller ❑Vibratory tamping roller ❑Static tamping roller or sheepsfoot ❑Crawler-tread equipment or bulldozer ❑Mechanical tamps or vibrator. Compaction  The compactor to be used is determined by the Contractor and is dependent upon several factors: ❑Size of embankment ❑Type of materials being compacted ❑Conditions of materials being compacted ❑Availability of equipments ❑Contractor’s preference. Compaction Compactor type Material Lift Depth 3 wheel All soils 8 in. max Smooth Drum All soils 8 in. max Vibratory Tamping-Foot Soil or shale Length of tamping foot Crawler-Tread rock Refer specifications Crawler-Tread aggregates 6 in. max Smooth drum aggregates 6 in. max Vibratory Mechanical Tamp or soils 6 in. max Vibratory Mechanical tamp or aggregates 4 in. max Vibratory Compaction Sloping Function of the natural angle of repose, density, surface and subsurface water flow. Early stabilization of surfaces is critical in construction. Eliminate points of concentrated flow using slope drains as outlets. Difficult slopes may require riprap, gabions, or other measures for permanent stabilization. Sloping Sloping Slope stabilization is important to ensure that failure or landslides will not occur. Properly designed slope protection and stabilization has to include two components: - a vegetational-biological and - a mechanical-structural component. For maximum effect, both components must be integrally planned prior to construction. Sloping Sloping KEYS TO SUCCESSFUL EARTHWORK OPERATIONS 1. Control surface and subsurface water 2. Maintain optimum moisture range by drying, mixing , or wetting 3. Identify and monitor cut & fill quantities 4. Good layout (horizontal & vertical control) 5. Minimize handling - minimize stockpiling KEYS TO SUCCESSFUL EARTHWORK OPERATIONS 6. Optimize haul lengths 7. Minimize cycle time 8. Proper selection and sizing of excavators and haul units 9. Alternate haul unit wheel paths 10. Experienced personnel in the field To be continue….. Links to learning materials Site clearing: https://www.youtube.com/watch?v=f3XKGOaqYUU Earthwork Cuts & Fills https://www.youtube.com/watch?v=dZKzPIvR5Wc Soil transportation https://www.youtube.com/watch?v=PY5z08F1_kk Compaction https://www.youtube.com/watch?v=MgvUDs5tcu0 Sloping https://www.youtube.com/watch?v=BBRI9QvWa4k https://www.youtube.com/watch?v=y8X2q5DWLH4 CUTTING AND EXCAVATION  Cutting and excavation Most construction projects require the movement of earthwork on site. This will result in altering the existing elevation to a different or finish elevation. To determine the amount of soil to be moved, the estimator needs to have a plot plan or topographic survey. This drawing is developed by plotting the readings (elevations) obtained from a topographic field survey usually performed by a licensed land surveyor.  Contour lines are lines drawn on a map connecting points of equal elevation. Contour lines show elevation and the shape of the terrain. They illustrate the land’s topography on the map  Types of Materials Purposes Cutting and excavation Cutting and excavation Classification of Excavation based on type of material: ❑ Topsoil excavation ❑ Earth excavation ❑ Rock excavation ❑ Muck excavation - this usually contains excess water and unsuitable soil ❑ Unclassified excavation - this is any combination of material types Cutting and excavation Classification of Excavation based on it purposes: ❑ Stripping ❑ Roadway excavation ❑ Drainage or structure excavation ❑ Bridge excavation ❑ Channel excavation ❑ Footing excavation ❑ Borrow excavation ❑ Dredge excavation Cutting and excavation Excavation can be either a part of the permanent works (e.g. cuttings) or a temporary expedient in the construction of the works (e.g. for foundations and drainage) The sides of the excavations are required to remain stable during their design life, can be achieved by: ❑ excavating the material to a stable slope angle ❑ retaining or supporting the material. Cutting and excavation Cutting and excavation Cut and Fill in during earthworks  Engineers need to concern themselves with issues of geotechnical engineering (such as soil density and strength) and with quantity estimation to ensure that soil volumes in the cuts match those of the fills, while minimizing the distance of movement.  In the past, volume analysis were done by hand using a slide rule and with methods such as Simpson's rule.  Nowadays, calculations can be performed with a computer and specialized software, including optimisation on haul cost and not haul distance. Cutting and excavation Cutting and excavation  Cut and Fill Calculation There are two basic methods for calculating cut and fill construction projects by hand The first is called the grid method The second is called the cross-section method  Cut and Fill Calculation The Grid Method 1. Lay your plan out on the flat surface. Then draw set of equally spaced horizontal and vertical lines across your plan. 2. At each intersection of the horizontal and vertical lines, determine the existing and the proposed new elevation 3. For each intersection subtract the existing Existing elevations elevation from the proposed elevation. Positive numbers are fill. Negative numbers are cut. Proposed elevations  The Grid Method…cont. 4. For each cell, add the four cut and fill numbers together and divide them by 4.0 to calculate the average cut or fill depth for that cell. Average Depth = (n1+n2+n3+n4)/4 5. Multiply the average cut or fill depth by the number of square meters/feet in the grid cell (Area to get the cut or fill volume in cubic meters/feet. V = Area x Avg. Depth m/f m/f Cell The Grid Method…cont. 6. Add all of the cut volumes up to get the total cut for the site in cubic meters/feet. 7. Add all of the fill volumes up to get the total fill for the site in cubic meters/feet. 8. To calculate the import or export, subtract the fill volume from the cut volume. If the result is a positive number, you have more cut than fill and you will need export material from your site. If the numbers negative, you will need to import dirt onto the building site.  Cut and Fill Calculation The Cross-section Method 1. Lay your plan out, and divide your plan Existing with a number of equally spaced elevations horizontal lines. vertical axis 2. On a piece of graph paper, plot out the existing elevations from the beginning to the end of each cross-section line. Proposed elevations Horizontal Axis  Cut and Fill Calculation 3. The vertical axis is for elevations and the horizontal axis is for the distance along the cross- section. 4. Then for each cross- Proposed new elevation section, plot out the Existing elevation proposed elevations from the beginning to the end of each cross-section line on the same graph as the existing. Construction Site  The Cross-section Method...Cont. 5. For each cross-section, count the number of squares where the existing line is above the proposed line. This is your cut area for that cross-section. Cut Area Fill Area 6. For each cross-section, count the number of squares where the existing line is below the proposed line. This is your fill area for that cross-section.  The Cross-section Method...Cont. 7. For each adjacent pair of cross- sections, average the cut area between the two and multiply it by the distance between the two cross-sections to calculate your cut volume. 8. For each adjacent pair of cross- sections, average the fill area between the two and multiply by Distance between two cross-sections the distance between the two cross-sections to calculate your fill volume.  The Cross-section Method...Cont. 9. Now add up all of your cut volumes to get the total cut volume for your site in cubic meters. 10.Add up all of your fill volumes to get the total fill volume for your site in cubic meters. 11.To determine the export for your site, subtract the fill volume from the cut volume. If this is a positive number, then you have more cut than fill so you’ll need to export material from your site. Red colour is cut Blue colour is fill If the numbers negative you have more fill than cut, and you will need to import material onto your building site. There is another method using software Can learn more about: Grid method Cross section method Software method From the link below and others: https://www.youtube.com/watch?v=TfqNK4v73nk QUIZ  CHAPTER 2: SUBSTRUCTURE Part 1 2.1 Building foundation: types and functions 2.1.1 Shallow Foundation - strip footings , pad footing, raft foundation. 1  Wind load Wind load Dead load 2 3  What is Substructure?  FOUNDATION is a part of SUBSTRUCTURE components  foundation is the lowest portion of the building structure. Extends from the bearing surface to the main structure.)  Usually located below the ground level.  A foundation is a part of the structure which is in direct contact with the ground to which the loads are transmitted.  Foundations can be located at; below ground, at ground level, or above ground level. 4  Deep Foundation Shallow Foundation 5 6  Main functions of the foundations  To supports the weight of structure and distribute the load of the structure over a greater area.  To transmit the load uniformly under the structure.  Anchors the structure to the earth, providing a firm, level and strong base over which the superstructure may be constructed. 7  Main functions of the foundations  To avoid any settlement or other movement that can cause damage to any part of the building (a stable foundation should bear the loads without sinking or settling more than an inch at the most).  To increase the stability of the structure by preventing its tilting or overturning against winds, earthquakes and uneven distribution of live load (Lateral Stability). 8  Selection Criteria  Loading of the building, big load need big foundation such as raft foundation or piling.  Types of soil such as peat soil prefer piling or deep foundation  Most economical but capable to support numbers of building or storey (pad footing or pilling?) 9  Selection Criteria  The loads that must be transferred from the structure to the soil strata supporting it. This also should evaluate the ability of the soil to support the ultimate loads.  The capability of the structure that will safely transfer the loads from the superstructure to the foundation bed.  The possibility and extent of settlement of the soil due to the presence of mines and quarries in the vicinity.  The possibility of the underground water has sulfates or other salts that can degrade the foundation materials. 10  Factors That Need To Be Considered in the Foundation Design  Soil Investigation (S.I) is needed to determine the subsoil includes the soil type, strength, soil structure, moisture conditions and the presence of roots.  Purpose of S.I-determine the bearing capacity, seasonal volume changes and other possible ground movements.  Common methods obtaining soil samples;  trial pits,  boreholes,  window sampling and  dynamic probe test. 11  Factors That Need To Be Considered in the Foundation Design  For more safety precaution use factor of safety FOS = 3  Increase number of bore hole or sufficient number of borehole so that the result of the report is more accurate.  Choose the critical point load for borehole  Every end of the building  Supervise the S.I properly make sure no mistake 12  Factors That Need To Be Considered in the Foundation Design  For the safety of the foundation design use the lowest of bearing capacity value.  The engineer must have good enough data for the S.I such as previous soil report, cutting or filling area.  Engineer also must make sure the original ground level and purposed level or formation level while designing the foundation. 13  Factors That Need To Be Considered in the Foundation Design  The correct parameter is important to prevent from foundation failure that may occur causing building collapse. It will cause a big loss of material and even peoples life. Highland Towers- Malaysia Overturning Shanghai-China residential building 14  Soil Quality Is The Key  Building rely on soil beneath to stay put. If the soil under the house moves up, down, or sideway, the house is in trouble.  The soil profile may be varies as we move across from side to side, and when we dig deeper downward.  Strong soil- weak soil type range from; STRONG Bedrock-gravel-course sand-fine sand-clay-silt-organic material. WEAK The following are the different types of soils on which foundations are constructed:  Soft soils - This soil is compressible and yields when loaded. Examples are clayey soil and loam. Small buildings or ordinary structures can be built on these types of soils.  Spreading soils - These are non-cohesive soils. Examples of this type of soil are sand and gravel.  Hard or rocky soils - These are incompressible and strong soils. They can withstand heavy loads without yielding. Multistoried buildings and water reservoirs are designed on such soils. 15  Types of Foundation Strip/Spread Footings Pad Footing/Foundation Shallow Raft/Mat Foundation End Bearing Pile Friction pile (spun pile, Deep bored pile, bakau pile and micro pile) combine 16  SHALLOW FOUNDATIONS RAFT FOUNDATIONS STRIP FOUNDATIONS PAD FOUNDATIONS 17  Strip Foundation  Most suitable, economical type of foundation for small building on compact soil.  Strip foundation should be build/construct on soil with high bearing capacity.  This type of foundation is also known as wall foundation or continues spread footing foundation.  Consist of continuous strip of steel-reinforced concrete, from centrally under load bearing walls.  The continuous strip serves as a level base on which the wall is build and the width is design to capable to support the load without undue compaction. 18  Strip Foundation  The greater the bearing capacity of the subsoil, the less the width of the foundation.  Width of strip foundations depends on the bearing capacity of the subsoil and the load on the foundations.  Refer table 3.2 for minimum width of strip foundations.  Types of strip foundations;  stepping strip,  wide strip and  narrow strip (trench fill or deep strip). 19  Characteristic of Spread/Strip Footings  Low Cost  Ease of construction  For small-medium size structures with moderate-good soil.  For large structures with exceptionally good soil or shallow bedrock.  Spread/strip footing may be built in different shapes and sizes to accommodate individual needs. 20  Types of spread footings based on size and shape Types of Spread No Footings Applicable 1 Square for a single centrally-located column 2 Rectangular when large moment load are present 3 Circular for light standards, flagpoles etc 4 Continuous for bearing walls (wall/strip footings) 5 Combined when columns are close together 6 Ring for walls of above-ground circular storage tanks Strap (cantilever when very close to a property line/other 7 footing) structure 21 22  In both situations shown the thickness (T) of the foundation should be equal to P or 150mm, whichever is greater T T T=P or 150mm (whichever greater) Foundation width Foundation width should be should not be less than not less than the the appropriate appropriate dimensions in dimension in Table 3.2 Table 3.2 plus offset dimensions A1 and A2 23  If P is greater than T, then the foundation may shear at 45° reducing the width of the foundation and bearing area. The foundation fails where tension is exerted on the P concrete T Shear failure angle 45° Following the shear failure, the load is concentrated on a smaller area, the ground may consolidate under the increased load 24   When strip foundation used in sloping sites-stepped the foundation.  The full thickness of the upper foundation should overlap twice twice the height of the step (O=2xT), or 300 mm whichever is greater.  The brickwork and blockwork on the top of the foundation should tie in at the step to avoid the needs of cutting bricks/blocks and to avoid the possibility of reducing the stability of the wall. STEPPING STRIP FOUNDATIONS 25  WIDE STRIP FOUNDATIONS Figure 8: Wide Strip Foundation  Wide strip foundations distribute loads over a larger area and reducing the load per unit area on the ground.  Wider strip foundation is most suitable for subsoil with poor bearing capacity such as soft sandy clays.  Widening and deepening the concrete foundation (to ensure the foundation does not shear) – uneconomical. Alternatively-form a strip of steel-reinforce concrete for safe-economical wide strip foundation (figure 8). 26  NARROW STRIP FOUNDATIONS  Also known as trench fill/deep strip foundation.  Suitable for good bearing soil with no seasonal volume change soil/clay; e.g: stiff clay.  The base of narrow/deep strip will extend up to a depth where the clay soil is unaffected by seasonal changes in moisture content.  50-mm thick compressible sheet material may needed to prevent lateral pressure to the sides of the foundation (saturated and dries out condition cause expansion and contraction of soil at the external face of the foundation) 27  Rectangular Spread Footings  It have plan dimension of B x L, where L is the longest dimension.  These are useful when obstructions prevent construction of a square footing with a sufficiently large base area and when large moment loads are present. 28  Circular Spread Footings  This foundation are round in plan view.  These are more frequently used as foundation for light standard, flagpoles, and power transmission line.  If these foundation extend to a large depth, they may be have more like a deep foundation. 29  Continuous Spread Footings  This type of foundation is also known as wall foundation or strip foundation.  It uses is to support bearing wall. 30  Ring Spread Footings  This footing are continuous footing that been wrapped into a circle.  This type of footing is commonly used to support the walls of above- ground circular storage tanks. 31  Forces pushing down must equal the forces pushing up - EQUILIBRIUM 32  Heave If the forces pushing up is greater than the forces pushing down the building will be pushed upwards – HEAVE If forces pushing down is greater than the forces pushing up the building will sink – SUBSIDENCE Subside 33  Problems if the rules are not The load spreads at about followed 400 through the foundation (P>T) 34  Loads Acting on the Foundation  The foundation has to bear more than just the load of the superstructure.  A load can be defined as anything, which exerts pressure or thrust on a structure.  The following are the different types of loads that act on the building foundation:  Live Load (Qk) - A live load or imposed load is a movable, temporary or transferable load. This can include moving vehicles, people walking or children jumping.  Dead Load (Gk)- This load is permanent and immovable. It is the non- transferable load of the structure itself.  Wind Load (Wk) - This load is applicable when the structure is tall.  Snow Load - This load is considered when the structure is situated in snowy, hilly areas. 35  Rock or soil Typical bearing value (kN/m2) Massive igneous 10,000 bedrock 2,000 to 4,000 Sandstone 600 to 2,000 Shales and mudstone 600 Gravel, sand and gravel, compact Medium dense sand 100 to 300 Loose fine sand Less than 100 Hard clay 300 to 600 Medium clay 100 to 300 Soft Clay Less than 75 36 Typical allowable bearing values 37  PAD FOUNDATION/FOOTING  Similar to continuous footings accept for they are usually lain under a single pier/column.  Pad foundation spread the load out (in a square) with the column/pier sitting in the middle of the square.  Can also be designed for loads of the walls and the buildings are transferred through ground beams that rest on the pad foundations.  The pad foundations will transfer the loads to a lower level where soil of sufficient load bearing strata exist. 38  Construction sequence of pad foundation Marked out and excavate The clean and leveled Formwork for the footing ground to correct level. ground then poured with installed at the correct Excavation level should up 50mm thickness lean position to good load bearing concrete. strata. After pad footing detailing inspected and approved than concrete can be poured and leave the foundation to dry (curing process) Install reinforcement according 39 to construction detailing  PAD FOUNDATION/FOOTING  The advantage of this system of foundation is that pockets of tipped stone or brick and concrete rubble that would obstruct bored pile may be removed as the pits are excavated.  The nature of subsoil also may be examined as the pits are dug to select a level of sound subsoil. 40  Square Footings 41  Combined Footing Foundation  In this type, the two walls or columns of a superstructure are provided with a single combined footing.  This is designed so that the center of gravity of the supporting area is in proportion to the center of gravity of the tow column loads.  These can be rectangular or These are usefull when trapezoidal in shape. columns are located too close together for each to have its own footing. 42  RAFT FOUNDATION  Depending on its position raft foundation also known as Mat foundation in floating position.  Sometimes also called as Floating Foundation.  Used where heavily constructed loads are to be distributed over a large surface area.  It is used where the soil is marshy, clayey or soft, with weak bearing capacity. 43  RAFT FOUNDATION  This consists of reinforced concrete slabs covering the entire area of construction, like a floor.  Always made of reinforced concrete. 44 SIMPLE RAFT FOUNDATION  RAFT FOUNDATION  If ground pressures are likely to be excessive at different seasons, reinforcement may be required; this is known as fabric when in sheet mesh form. REINFORCED RAFT FOUNDATION 45  Conditions for Raft/Mat Foundations -Structural loads require large area to spread the load -Soil is erratic and prone to differential settlements -Structural loads are erratic -Unevenly distributed lateral loads -Uplift loads are larger than spread footings can accommodate; -Mat foundations are easier to waterproof 46  CHAPTER 2: SUBSTRUCTURE Summary Building foundation: 1. Shallow Foundation ❑ Strip footings , ❑ Pad footing, 47 ❑ Raft foundation.  CHAPTER 2: SUBSTRUCTURE Summary Building foundation: 1. Deep Foundation ❑ Driven pile , Methods: 1. End bearing pile. ❑ Drilled pile, 2. Friction pile. ❑ Spun pile. 48 ❑ Bored pile.  CHAPTER 2: SUBSTRUCTURE Part 2 2.1.2 Deep Foundation ❑ Piles Driven pile Drilled pile spun pile bore pile 1  DEEP FOUNDATION 2  DEEP FOUNDATION Reasons why Deep Foundation?? Conventional strip foundations is uneconomical to excavate. The bearing ground located at some distance below the surface level of the made up ground. A solution is to use deep/pile foundation to support reinforced concrete ground beams on which walls are raise. The pile/deep foundation takes the load of the building through made-up ground or week soil to load-bearing strata. The ground beams transfer the building loads to the piles. Piles are a convenient method of foundation for works over water, such as jetties or bridge piers. 3  Main Components of Deep Foundation Pile Deep Foundation Pile Cap 4  DEEP FOUNDATION  Piles are long and slender members which transfer the load to deeper soil or rock of high bearing capacity avoiding shallow soil of low bearing capacity.  The main types of materials used for deep piles are wood, steel and concrete.  Piles made from these materials are driven, drilled or jacked into the ground and connected to pile caps.  Main functions of a pile; i. to transmit a foundation load to a solid ground ii. to resist vertical, lateral and uplift load 5  Driven pile spun pile RC pile 6  Drilled pile bore pile 7 8  Factors Influencing The Choice of Pile Location and Ground Conditions Durability Cost Type of Structures Ground containing Over water Boulders- Concrete Installation cost clay with On Land Steel materials ground heave Not causing vibration Loose water to existing/nearby Timber time bearing sand Structures- Heavy Structure Under-reamed bases Test load Existing Structure Supervision Organization, 9 overhead and etc.  Factors Influencing the Choice of Pile Location and type of structures  For structures over water, such as wharves and jetties, driven piles or driven cast-in-place piles (in which the shell remains in place) are the most suitable.  On land, driven cast-in-place types are usually the cheapest for moderate loadings.  It is necessary for piles to be installed without causing any significant ground heave or vibrations because of their proximity to existing structures, the bored cast- in-place pile is the most suitable.  For heavy structures exerting large foundation loads, large-diameter bored piles are usually the most economical.  Jacked piles are suitable for underpinning existing 10 structures.  Factors Influencing the Choice of Pile Ground conditions  Driven piles cannot be used economically in ground containing boulders (large rocks), or in clays when ground heave would be detrimental.  Bored piles would not be suitable in loose water- bearing sand, and under-reamed bases cannot be used in cohesion less soils since they are susceptible to collapse before the concrete can be placed. 11  Factors Influencing the Choice of Pile Durability  Most important criteria especially in the choice of material. For example, concrete piles are usually used in marine conditions since steel piles are susceptible to corrosion in marine conditions.  timber piles is not the most suitable type under marine conditions because it can be attacked by boring molluscs.  On land, concrete piles are not the best choice, especially where the soil contains sulphates or other harmful substances. 12  Factors Influencing the Choice of Pile Cost  Considerable important decision over the choice of pile.  The overall cost of installing piles includes:  the actual cost of the material,  the times required for piling in the construction plan,  test loading,  cost of the engineer to oversee installation and loading  cost of organisation and overheads incurred between the time of initial site clearance and the time when construction of the superstructure can proceed. 13  Classification of Pile With Respect to Load Transmission and Functional Behavior  End bearing piles (point bearing piles)  Friction piles (cohesion piles )  Combination of friction and cohesion piles 14  END BEARING PILE 15  End bearing piles  Typical end-bearing piles are driven through very soft soil, such as a loose silt- bearing stratum underlying by compressible strata.  This pile acts on the basic concept of digging through the top soil (relatively weak) to an underlying firmer rock to anchor the foundation.  The piles transfer their load on to a firm stratum located at a considerable depth below the base of the structure. 16  This pile behaves as an ordinary column. In weak soil, this pile will not fail by buckling End bearing piles 17  End bearing piles-cast in place 18  End bearing piles - driven or jacking (R.C or Steel Pile) 19  Piling Rig 20  Pile Driving 21  FRICTION PILE 22  Friction piles  Friction piles, also known as floating pile foundations,  Commonly used in construction to provide underground support for buildings, bridges, docks and other structures.  They are often used when end-bearing piles are not suitable.  Friction piles rely specifically on the friction created between the soil and the surface of the pile material in order to provide stability.  The combination of friction and adhesion with the soil causes them to stay in place. 23  Friction piles  The load is transferred to the adjoining soil by friction between the pile and the surrounding soil.  The load is transferred downward and laterally to the soil.  In order for friction piles to be effective, the soil surrounding the area must be fairly uniform in type and density.  For more complex situations, construction companies sometimes rely on a combination of friction and end-bearing piles. 24  Friction Pile Types Placement Installation Repetition of pile of Pile process Driven Cast-in-situ 25  SPUN PILE 26  Spun Pile Standard Characteristics  Pre-stressed concrete spun pile (cast in the factory) and deliver to site for installation.  Size : 250mm to 1000mm diameter  Lengths : 6m, 9m and 12m (Typical)  Structural Capacity : 45Ton to 520Ton  Material : Grade 60MPa & 80MPa Concrete  Joints: Welded  Installation Method : –Drop Hammer –Jack-In 27  Spun Pile 28  Spun Piles Vs. RC Square Piles Spun Piles have …  Better Bending Resistance  Higher Axial Capacity  Better Manufacturing Quality  Able to Sustain Higher Driving Stresses  Higher Tensile Capacity  Easier to Check Integrity of Pile  Similar cost as RC Square Piles with higher pile integrity 29 Advantages & Disadvantages of Spun Pile No Advantages Disadvantages 1 Best suited for use as friction piles that Expensive to splice and cut don't meet refusal during driving (refusal: pile can't be driven any further, so it becomes necessary to cut off the portion) 2 Best suited for toe-bearing piles where the Difficult to cut required length is uniform and predictable 3 Less expensive than steel piles Susceptible to damage during handling or driving 4 Have a large load capacity Not suited for hard driving conditions 30  BORE PILE 31  Bored piles Foundation structure made of reinforced concrete on site. Used to carry heavy loads by transmitting the load to a stable soil strata. Varies in diameter and depth. Dimension varies from 450mm to 2000mm. Designers will decide the size according to the load requirement and as well as the soil condition of the site. widely used and can be constructed in most soil condition and over water. 32  Bored Pile Construction Bored piles is constructed by first drilling a hole in the ground until a competent load bearing layer is reached. Once achieved, a reinforcement steel cage is lowered into the drilled hole and the hole is filled with concrete. It is also known as cast in place piles. 33  Bored piles  High flexibility and are widely used in deep foundation for :-  high rise buildings,  jetties,  bridge foundation and  as vertical retaining structures like a retaining wall or sheet piles wall. (In this case the bored piles is known as contiguous bored pile wall).  Designed either as a point bearing piles or friction piles.  If competent load bearing layer like bed rock is present, then the bored piles will be designed as an end-bearing pile. This means that the load carrying capacity of the piles is mainly derived from the bearing capacity of the rock layer at the toe of the pile. 34 Bored Piles  Bored pile-single pile - pile groups. 35  can be inclined to a certain angle. When bored piles are Angle bored piles also known as constructed close to one raked piles (found in structures that another or overlapping slightly, this is known as contiguous requires resistance to horizontal bored piles wall or secant piles load like in a retaining wall or bridge wall. and piers foundation). 36 Standard Bored Piles Characteristics Considerations…  Size : 450mm to 2000mm  Borepile Base Difficult to Clean  Lengths : Varies  Bulging / Necking  Structural Capacity : 80Ton to 2,300Tons  Collapse of Sidewall  Concrete Grade : 20MPa to 30MPa  Dispute on Level of Weathered  Joints : None Rock  Installation Method : Drill then Cast-In-Situ 37 38 39 40 41 42 43 44 45 46 47 Advantages & Disadvantages Bore Pile No Advantages Disadvantages 1 Less costs of mobilizing and demobilizing a drill rig Dependent on contractor's skills 2 Less noise and vibration Lower unit end bearing capacity 3 Soils excavated can be observed and classified Expensive for full-scale load test during drilling 4 Size of shafts can easily be changed during const. 5 Can penetrate soils with cobbles, boulders and many types of bedrock 6 Possible to support each column with one large shaft (no pile cap) 48  CHAPTER 2: SUBSTRUCTURE Part 3 2.1.2 Deep Foundation micro pile, pile cap 2.2 Column stump, ground beam, ground slab 1  MICROPILE 2  Micropiles  Size : 100mm to 350mm Diameter  Lengths : Varies  Structural Capacity : 20Ton to 250Ton  Material : Grade 25MPa to 35MPa Grout  N80 API Pipe as Reinforcement  Joints: None  Installation Method : –Drill then Cast-In-Situ –Percussion then Cast-In-Situ 3  Micropiles  Micropiles also known mini piles.  Applicable for foundations of a wide variety of construction projects such as highways, bridges and even transmission towers.  Can be installed at varying angles i.e. from vertical to obtuse (angle between 90-180 degree incline).  Highly capable of resisting both lateral and axial loads due to the fact that they are made of steel with varying diameters of between 70 to 200 mm.  Sheer ability to provide a combination of both tensile and compressive resistance, micropiles tend to be quite useful where there is a need for resistance to uplift.  Very little or no vibration at all. 4  Technological process of carrying out micropiles 2a) realization of a borehole with the rotary technology 2b) pulling out drilling tools and filling the hole with grout 2c) setting a reinforcement thick-walled steel pipe 2d) grouting of the micropile root part 2e) finished micropile Pressure-grouted micropiles construction 5  Securing overburdens of underground works (tunnels, galleries) with the use of a micropile umbrella Examples of underpinnings of existing structures with the use of micropile space piers or individual micropiles Carrying out pipe micropiles to protect the driven 6 tunnel calotte, the New Connection in Prague 7  Cast in-situ micropile construction 8  Timber/Bakau Pile  Timber is a hugely capable civil engineering material, with the additional advantage of being sustainable.  Trees, in particular conifers, make natural piles.  Timber foundations may be particularly suitable for countryside structures such as bridges, forest chalets and activity centres, as well as post-and- beam timber buildings in waterfront or flood prone locations.  Preservative treated softwood or durable hardwood timber can be used for the construction of retaining walls, bank seats, and for foundation pads 9 and footings.  Timber/Bakau Pile  For many structures, timber piles are a highly suitable choice of foundation, given appropriate ground conditions.  They are economical, easy to transport, handle, cut to length and work with on site; and particularly suited for locations with access difficulties, or where excavations and the delivery of concrete would pose problems.  Short, driven timber piles can be the solution for foundations in ground with a high water table, and where firm strata exists below surface material of loose sand, soft clays, or organic soils. 10  Timber/Bakau Pile  In deep silt deposits, where the capacity of the pile is determined by shaft friction, timber piles are especially suitable being tapered and easy to splice.  Timber piles are suitable to be used below the water table, where they have proved practically invulnerable to decay, and extended to the surface using concrete sections.  They are resistant to acidic and alkaline soils, and soils with high sulphate or free carbon dioxide content.  Timber piles can also be driven for ground improvement, to density loose granular soils.  For the decay reason-treated with preservatives such as creosote oil which impregnated into the wood (preventing dry-rotting and against damage from most animal and plant attack) 11  Timber/Bakau Pile  The installation of timber piles is a process that involves dropping a weight on top of the pile in order to drive the pile into the ground.  Timber piles have been used for centuries to support man-made structures.  The equipment that is used to install timber piles includes a crane, a boom, a set of leads, a hammer, a helmet, a pile gate, pile monkey, and pile (see Figure). 12  Advantages & Disadvantages Bakau pile No Advantages Disadvantages 1 Low construction cost Medium axial loads (100 - 400 kN) 2 Used as waterfront structures Susceptible to decay Susceptible to damage when 3 For light driving conditions driving (in loose sands and soft to medium clays) 13  Piling Techniques  Damage during driving can be controlled by using proper technique.  Among the soultions are:- √ Using lightweight hammers √ Using steel bands near butt √ Using a steel shoe on the toe √ Pre-drilling 14  Drilled Equipments  Drilling Rigs  Truck-mounted drilling rig  For usual shaft, d=500 – 1200mm and H=6.24m  Specialized rigs  A-Shaped Frame Rigs 15   Drilling Tools ▪ The helix-shaped flight auger (most common used) – Effective in most sols and soft rocks ▪ Augers with hardened teeth and pilot stingers – Effective in hardpan or moderately hard rock ▪ Spiral-shaped rooting tools – Help loosen cobbles and boulders 16  ▪ Bucket augers – To collect cuttings in a cylindrical bucket – Used in running sands ▪ Belling buckets Bucket augers – To enlarge the bottom of the shaft (bells or under reams) ▪ Core barrels – To cut a circular slot creating a removable core – Used in hard rock ▪ Multi-roller percussion bits – To cut through hard rock ▪ Cleanout buckets – To remove final cuttings from hole Belling bucket 17  Drilled Techniques  Drilling in Firm Soils  Using dry method (open-hole method)  Most common used: simple, economy and good reability  Steps:  Holes usually advance using conventional flight auger  Holes remain open without any special support  Check the open hole for cleanliness and alignment  Insert steel reinforcing cage  Pour the concrete 18 19   Drilling in Caving (Cave-in) or Squeezing Soils  Caving:  The side of a hole which is collapse before or during concrete placement.  Usually in clean sands below the groundwater table.  Squeezing:  The sides of hole bulging inward during or after drilling  Usually in soft clays and silts or highly organic soils.  Most common techniques:  Using casing  Drilling fluid (slurry method) using bentonite clay or attapulgite clay. 20  PILE CAP 21  PILE CAP Pile Cap (BS 8004), “a pile cap is defined as a concrete block cast on the head of a pile, or a group of piles, to transmit the load from the structure to the pile or group of piles”. Pile cap transfers the load form the structures to a pile / pile group, then the load further transfers to from soil. Pile caps are thus incorporated in order to tie the pile heads together so that individual pile movement and settlement is greatly reduced. The stability of the pile group is greatly 22 increased.  stump, varius H 23  Foundations relying on driven piles often have groups of piles connected by a pile cap (a large concrete block into which the heads of the piles are embedded) to distribute loads which are larger than one pile can bear. Pile caps and isolated piles are typically connected with grade beams to tie the foundation elements together; lighter structural elements bear on the grade beams while heavier elements bear directly on the pile cap. 24  Pile Arrangement below pile cap raked RC vertical SP Mic RC SP BP Mic 25  Pile cap  Function:  To distribute the structural loads to the piles.  To tie the piles together so they can act as a unit.  To laterally stabilise individual piles thus increasing overall stability of the group  To provide the necessary combined resistance to stresses set up by the superstructure and/or ground movement 26  COLUMN STUMP 27  Column Stump  The stump is the simplest and most familiar footing used for the vertical support and the transfer of building loads to the foundation.  Stumps are used to support timber-framed houses for which they are currently the most cost effective.  Three types of materials are commonly used for stumps:  timber  concrete  steel.  Stumps must have a concrete or timber footing placed underneath the base of the stump. This is to spread the load transferred to the stump from the building. This support beneath the stump is called a 'pad' or 'soleplate'.  Usually concrete stumps are provided with concrete pads poured in situ on the site. Timber stumps are provided with timber soleplates. 28 29  GROUND BEAM 30  2.1 GROUND BEAM AND SLAB  Beams and slab are normally named by its location.  Ground beam refers to the structure of beam located on the ground.  Ground Beams are designed to support brick/blockwork or to form a permanent shutter to the edge of in-situ concrete floor slab.  The amount of reinforcement introduced into the design will be used to suit specific loading requirements and the beams can be designed to withstand any heave forces with the use of void forming or compressible materials. 31  Ordinary Ground Beam GB  This type of ground beam is the most used in building construction. lean con  It is the beam which both its ends are tied up at the column and lying between stump the two column. pad footing / pile cap  The beam fixes and holds fitly the columns in order to stabilize it.  In addition, it also acts to bear all the loads come from the wall which constructed parallel with the beam. 32  ORDINARY GROUND BEAM  A ground beam normally should consist of following items;  Reinforcements,  Concrete,  Linkers  The reinforcements can be placed at center of that beam.  The sizes of main reinforcement play important role in determine the strength of a beam.  Ground beam usually does not have secondary beam, only has primary beam. 33  12 meter length of rebar bar bending schedule plan without wastage ORDINARY GROUND BEAM column GB and GSLAB 1. non suspended 2. suspended slab thick of beam or withd of beam extra big 34  GROUND CANTILEVER BEAM The cantilever beam is same as the beam explained before but only one end of cantilever beam is tied up at the column stump. The other end is free without joint with any column. The cantilever beam usually used for external structure such as beam for corridor and also partition wall outside the building.  The functions of ground cantilever beam are almost same but it cannot bear the loading such the ordinary beam. This is because, one end of that beam is not holding by any structure. As a result, it does not achieves the strength like the ordinary beam 35  Beam Construction Method  The ground beam construction starts after a column stump has been fixed in the foundation as needed.  Beam formwork will be placed tidy so that it look tough and strong to ensure that formwork does not move or expand during concreting work.  After that, The reinforcements will be installed along with linkers and surrounded by block spacers below and at the sides  Purpose of the spacer block is to keep the steel in place and to protect the reinforcement from corrosion due to aggressive chemicals. 36  Important during the ground beam construction clearing the ground. The span between the columns or piers is compacted. A blinding layer is done with quarry dust. Spacers are placed with Spacers sufficient number The reinforcements are then tied and bent separately. The reinforcement is laid straight with spacer blocks put at the bottom and sides 37  R.C. BEAM CONSTRUCTION PROCESS Formwork Reinforcements Removal of Formwork Concreting 38  Ground Beam The ground beam construction procedure (10 steps); 1. clearing the ground. 2. The span between the columns or piers is rammed and compacted. 3. A blinding layer is done with quarry dust. 4. The column or pier reinforcements should be left a foot high to join with the beam. 5. The reinforcements are then tied and bent separately. 6. Once ready, they are carried and laid over the columns and blinding. 7. The reinforcement is laid straight with spacer blocks put at the bottom. 8. Once the beam steel is in place, form work is erected to the sides. These must be firmed into the ground and made very tight. This will prevent the escape of the cement slurry when vibrating. 9. After the form work is complete, concrete is prepared and poured into the forms. The process continues while vibrating to ensure the concrete is well bonded with the steel. 10.The top is tamped to be smooth. The forms are removed after seven days while curing. 39  GROUND SLAB 40  Ground Slab  In construction, slab can be design in two conditions. is built when the ground is good enough to carry the load from the building. Non-suspended 1 In this condition, the slab is designed to slab carry the load of the building with the help from the ground support. is built when the ground is not good enough to carry the load from the building. In this condition, the slab is designed 2 just like the floor of upper floor that Suspended slab can carry the load without the help from the ground support. In this case, more cost is needed. 41  Ground Slab Damp Proof Course Damp-proof membrane 42  Ground Slab  Function of ground slab:  To support column and stump  To received the load from the building  To reduce the pressure on the column and stump  The main base of construction to ensure that the construction is done well  Create the easier job on floor finishes  The construction of a solid ground slab floor should includes:  Hardcore  Binding  Concrete bed or slab 43  Ground Slab Hardcore  The purpose of hardcore is to fill in any small pockets occur during site excavation, to provide firm base on which to place a concrete bed and to help spread any point loads over the greater area. It also acts against capillary action of moisture within the soil.  Hardcore is usually laid in layers of 100-150 mm to the required depth, and its is important that each layer is well compacted, using a roller if necessary, to prevent any unacceptable settlement beneath the solid floor. 44  Ground Slab Binding  This is used to provide clean, level and dry surface of hardcore if a damp-proof membrane (DPM) is to be place under the concrete bed or if a reinforced concrete bed is specified.  First, it will prevent the damp-proof membrane from being punctured by the hardcore and, second, it will provide a true surface from which the reinforcement can be positioned.  Blinding generally consists of a layer of sand 25-50 mm thick or a 50-75 mm layer of weak concrete (1:12 mix usually suitable) if a true surface of a reinforced concrete is required. 45  Ground Slab Concrete bed  Unreinforced or plain in-situ concrete, 100-150 mm thick;  Reinforce concrete, 150 mm minimum  Suitable concrete mixes are produced to BS EN 206-1:  The reinforcement used in concrete beds for domestic work is usually in the form of welded steel fabric to BS4483.  Sometimes a light square mesh fabric is placed 25mm form the upper surface of the concrete bed to prevent surface crazing and limit the size of any cracking.  In domestic work the areas of concrete are defined by the room sizes, and it is not usually necessary to include expansion or construction joints the construction of the bed 46  Concrete Reinforcement Mesh 47  Ground Slab Other materials needed for ground slab: (1) Damp Proof Membrane (DPM)  Water penetration is a prime cause of deterioration in building structures and materials and the presence of excess moisture encourages the growth of moulds and wood rotting fungi. Because of this, building regulations require that buildings are so designed that water neither damages the fabric nor penetrates to the interior where it may constitute a health hazard as well as spoiling decorations. 48  Ground Slab  Other materials needed for ground slab: (2) Damp Proof Course (DPC)  DPC is a physical barrier inserted into the fabric of a building to stop water passing from one place to another. This can be on a horizontal plane, stopping water rising up from the ground by being sucked up by the dry masonry above, or vertically to stop water passing from the outside of a building, though the masonry, to the inside. DPC's have taken many forms through the ages and one of the earliest forms was to use a layer of slate in the construction. Slate is still used but the less expensive plastic version ( below right ) is now more widely used. 49  END OF CHAPTER 1 Thank you 50