Singapore Polytechnic BE8133 Geomatics PDF

Official (Closed), Non-Sensitive SINGAPORE POLYTECHNIC SCHOOL OF ARCHITECTURE & THE BUILT ENVIRONMENT COURSE: DCE 1 FT MODULE CODE: BE8133 MODULE NAME: GEOMATICS TOPIC 3: LONGITUDINAL AN...

Official (Closed), Non-Sensitive SINGAPORE POLYTECHNIC SCHOOL OF ARCHITECTURE & THE BUILT ENVIRONMENT COURSE: DCE 1 FT MODULE CODE: BE8133 MODULE NAME: GEOMATICS TOPIC 3: LONGITUDINAL AND CROSS-SECTIONS Types of Plans Establish sufficient TBMs from a known For design and construction purposes: - benchmark along the proposed worksite. Topographical Plans Set the level instrument at a suitable position so that as many points as Longitudinal Sections possible along the section could be Cross Sections observed. Contour Maps Levels along the sections (long and cross-sections) are observed at regular For setting out design or proposed levels: - intervals. Setting out formation levels. Measure horizontal distances between all the points where levels were taken. Sectioning These distances are accumulated from Whenever works of long length like roads, the first (or starting) point such that all sewers, drains, bridges etc. are to be points have a “Running Chainage”. constructed, a survey to prepare a ‘Close’ the levelling work to known longitudinal section and cross-sections benchmarks. must be undertaken. Reduce the levels and apply all checks. A Longitudinal Section is a vertical section Refer to Practical Procedure for detailed along the centre line of the complete length explanation of the fieldworks. of the work. Plotting of Longitudinal Section A Cross-Section is a vertical section taken at the right angles to the centre line of the Horizontal scale should be the same work. scale as the site plan. Vertical scale is exaggerated to enable the difference in Provide data for: - height variations to be readily seen – Selecting suitable gradients for usually enlarged ten times the designing construction works i.e. roads, Horizontal scale. drains, sewers, bridges etc. Study or examine the RLs and select the Calculating earthworks quantities e.g. lowest value. volumes Draw a horizontal line to represent an Calculating depths of excavation arbitrary datum some way below the (cutting) or heights of filling. lowest value of the section. Plot the horizontal chainages to required Fieldworks for Longitudinal Section scale along the datum line and erect perpendicular lines at each chainage Set out or peg out the proposed centre point. line of the work on the ground at regular intervals. BE8133 – Topic 3 Page 1 of 2  Official (Closed), Non-Sensitive Scale the Reduced level of each Make sure that sufficient levels are taken chainage point along the perpendicular to cover slightly more than the total line from the datum line. width of the work. Join the chainage points plotted by straight lines as shown to produce the Plotting of Cross-Sections exaggerated longitudinal section Presentation and Plotting is the same as for the longitudinal section. Note: The lines joining the points MUST However Cross-Sections are plotted to NOT be drawn as curves since all levels the Natural Scale i.e. the H-scale and V- have been taken at changes of slope and scale are the same. therefore the gradient between any two Reduce the levels. points is constant. A line representing the arbitrary datum is selected and drawn for each section Plot the proposed or designed work on the drawing. Scale the chainages to the left and right of the centre-line. The following are usually added: - o Formation Level which is the level to Erect perpendiculars at chainages and which the construction work is to be scale the RL of each point. excavated or filled to. Join the plotted points to form a natural o Finished Level which is the level of profile of the ground. the completed work. Plot the formation levels, the formation The gradients of the formation levels are width and side slopes shown and the levels at each chainage point are calculated and tabulated in the drawing. Calculation of Cut and Fill The difference between the existing and formation (or proposed) levels at each chainage point are calculated and shown as Cut or Fill. RL Difference = Existing RL – Proposed RL Positive (+) RL Difference  Cut (Excess of material) Negative (–) RL Difference  Fill (Shortage of material) Fieldworks for Cross-Section Fieldwork is basically the same to that of observing for a Longitudinal Section. Levels are observed at regular intervals and at changes of slope and their distances measured from the point on the centre-line (left or right of the centre line). BE8133 – Topic 3 Page 2 of 2