Site & Subsoil Investigation PDF

Site & Subsoil Investigation Learning Outcome: Demonstrate proficiency in various methods of site investigation. Evaluate and select appropriate investigation methods based on site characteristics, project requirements, and environmental considerations. Apply acquired knowledge to asses...

Site & Subsoil Investigation Learning Outcome: Demonstrate proficiency in various methods of site investigation. Evaluate and select appropriate investigation methods based on site characteristics, project requirements, and environmental considerations. Apply acquired knowledge to assess foundation design requirements, slope stability, and ground improvement techniques based on the analysed subsoil characteristics. 2 Introduction What are Site Investigations? A Site investigation Could either be a walk over the site or a full topographical survey, this depends on the Size of the Project 3 What is the Purpose of site investigations? To determine any planning constraints. Previous planning permissions Presence of listed buildings on site Presence of Trees with preservation orders Location of permitted building line Characteristics of existing buildings presence of footpaths/ cycle ways visibility restraints on adjoining roads What is the Purpose of site investigations? To determine the character of the site and surrounding areas. The shape and size of the site Direction and degree of slope of the site site location and proximity to landmarks surface features buildings which must be demolished evidence of old foundations outcrops of rocks at the surface What is the Purpose of site investigations? To determine the proximity of services. Services include: Electricity Water Gas Drainage How do you obtain these information on site ? What is the Purpose of site investigations? To determine any legal considerations. The deeds to the property is checked to ensure: The physical boundaries are right There is no right of access granted to other parties There are no public rights of way crossing the site There are no restrictions What is the Purpose of site investigations? Study access into and around the site. Access into the site in relation to space and visibility on adjoining roads Determine traffic usage of the roads Assess the ease of movement for delivery vehicles Check for on and off-street parking Checks for frequency and duration of traffic hold ups in the area What is the Purpose of site investigations? Determine the nature of the subsoil strata under the site. Subsoil investigations done with reference to geological maps of the area. Ordnance survey maps Information from residents Evidence of flooding Information from British coal 10 Stages in site investigation BS 5930 code of practice: site investigations 1981 11 Walk over survey – Above the ground on and around the site Drainage Degree and direction of Design of Foundation slope Landscaping Soil Type Type of Vegetation Moisture Content Presence of Trees Presence of Surface water Ground water  Walk over survey Existing Buildings Obstructions Power/ Telecom cables Manholes Evidence of Services Inspection chambers below Ground Access into site Roads checked for limitations  Desk Study Data collected from walk over survey is reviewed together with maps, plans, records to produce a preliminary report Resources needed for Desk Study What Information Can you derive from these Resources ?  T/F 1. All projects require a topographic survey? 2. The main purpose of a site investigation is to check existing services? 3. Small projects always require Lab testing of subsoil samples 4. Existing buildings should be recorded on the site survey 5. It is important to check the capacity of existing services near a site 6. Old foundations and basements do not cause problems on construction sites 7. Local builders and developers are useful sources of information 8. Local traffic usage of roads should be checked 9. The desk study is performed after all soils testing is complete 10.The size of trees should be measured on site 17  Subsoil Investigation This Stage happens after the walk over survey and desk study, and depends on: 18 19 Methods of subsoil investigations Trial Pits Hand Auger Mechanical Boring ❖ Used for small scale ❖ Used for small scale ❖ Mechanical means of projects projects driving an auger into ❖ Subsoil inspected in-situ ❖ Suitable for soils which the ground to the will stand unsupported required depth usually ❖ Pit can be dug by hand deeper than 6m or machine ❖ Can be used to a depth ❖ Depths greater than 5m of 6m are usually not economic 20  Trial Pits - Methodology Site Selection. Excavation Layer Identification Sampling In-situ Tests Recording Data. Backfilling 21 Advantages Visual Cost- Sampling Examination Effectiveness 22  Disadvantages Surface Stability Disturbance Issues Safety Concerns Despite these disadvantages, trial pits are still widely used because they provide a direct method for geotechnical engineers to see materials in-situ. 23 Hand Auger A hand auger is usually a stainless- steel cylinder (bucket) approximately 3 to 4 inches in diameter and 1 foot in These are designed to sample soils at length. It is open at both ends with the depths up to about 3.0m, depending bottom edge designed to advance on the soil type perpendicular to the ground surface with a twisting motion into unconsolidated subsurface material to obtain a soil sample. 24 ❖ There are different types of hand augers designed for specific soil types. For example, the Edelman auger is designed for use in sandy soils and clay soils, while the stony soil auger is designed for soils with a large gravel content. ❖ Hand augers are used to measure subsurface soil properties. This method allows us to accurately calculate depths to soil horizons and determine the depth of the groundwater table. 25  Mechanical Boring Mechanical boring is a technique for site investigation that involves drilling holes into the ground to collect soil samples, perform in-situ tests, or install monitoring devices. 26 Mechanical boring can be used for various purposes, such as determining the soil stratigraphy, strength, stiffness, permeability, groundwater level, and contamination. Mechanical boring can also provide information for designing foundations, embankments, cuttings, roads, pipelines, and other structures 27 There are different types of mechanical boring methods, depending on the depth of investigation, the ground conditions, the type of samples and tests required, and the available equipment. 28 Task Compare the 3 methods of subsoil investigation. Write down your thoughts on the Padlet 29