Week 01 Preliminaries Works, Soil Investigate & Ground Water Control


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Week 01 Preliminaries Works, Soil Investigate & Ground Water Control

  1. 1. SITE PREPARATIONS Site Investigation Soil Investigation Ground Water Control Preliminaries Works Prepared by: Mr. Syamsul Hendra Mahmud Faculty of Built Environment, UTM
  2. 2. Introduction <ul><li>Every site are different? Why? </li></ul><ul><li>What are the difference between site investigation and soil investigation? Please give some examples? </li></ul><ul><li>Why we need to have site and soil investigation? </li></ul>
  3. 3. Site Investigation <ul><li>Aim is to collect systematically and record all the necessary data which will be needed or will help in the design and construction processes of the proposed work. </li></ul><ul><li>Site investigation includes the overall investigation of the site and it may consists of roads and access analysis, pipes and services analysis, location, development costs and environment analysis, plans etc. </li></ul><ul><li>It also consists of soil investigation which covers the analysis of the existing soil. </li></ul>
  4. 4. Site Investigation <ul><li>Stages of site investigation </li></ul><ul><ul><li>Desk study </li></ul></ul><ul><ul><li>Visiting analysis </li></ul></ul><ul><ul><li>Topography and hydrology analysis </li></ul></ul><ul><ul><li>Construction progress analysis </li></ul></ul><ul><li>Follows BS 5930 : 1981 “Code of Practice for Site Investigation” </li></ul>
  5. 5. Soil Investigation <ul><li>Specifically related to the subsoil beneath the site under investigation and could be part of or separate from the site investigation. </li></ul><ul><li>Objectives: </li></ul><ul><ul><li>Determine the suitability of the site for the proposed projects. </li></ul></ul><ul><ul><li>Determine an adequate and economic foundation design. </li></ul></ul><ul><ul><li>Determine the difficulties which may arise during the construction process and period. </li></ul></ul><ul><ul><li>Determine the occurrence and/or cause of all changes in subsoil conditions. </li></ul></ul>
  6. 6. Soil Investigation <ul><li>How: in a fully annotated and dimensioned plans and sections. </li></ul><ul><li>Includes: any elements on adjacent sites which may affect the proposed works or conversely anything appertaining to the proposed works which may affect an adjacent site should also be recorded. </li></ul>
  7. 7. Soil Investigation <ul><li>Soil samples: </li></ul><ul><ul><li>Disturbed soil samples : these are soil samples obtained from boreholes and trial pits. The method of extraction disturbs the natural structure of the subsoil but such samples are suitable for visual grading, establishing moisture content and some laboratory test. Disturbed samples should be stored in labelled air tight jars. </li></ul></ul>
  8. 8. Soil Investigation <ul><li>Soil samples: </li></ul><ul><ul><li>Undisturbed soil samples : these are soil samples obtained using coring tools which preserve the natural structure and properties of the subsoil. The extracted undisturbed soil samples are labelled and laid in wooden boxes for dispatch to a laboratory for testing. This method is suitable for rock and clay subsoils but difficulties can be experienced in trying to obtain undisturbed samples in other types of subsoil. </li></ul></ul>
  9. 9. Soil Investigation <ul><li>Methods </li></ul><ul><ul><li>Trial pits </li></ul></ul><ul><ul><li>Hand or mechanical auger </li></ul></ul><ul><ul><li>Mechanical auger </li></ul></ul><ul><ul><li>Sampling shells </li></ul></ul><ul><ul><li>Wash boring </li></ul></ul><ul><ul><li>Mud rotary drilling </li></ul></ul><ul><ul><li>Core drilling </li></ul></ul>
  10. 10. Soil Investigation <ul><li>Soil assessment and testing </li></ul><ul><ul><li>Are designed to evaluate the density or shear strength of soils and are very valuable since they do not disturb the soil under test. </li></ul></ul><ul><ul><li>Type of tests: </li></ul></ul><ul><ul><ul><li>Standard penetration test </li></ul></ul></ul><ul><ul><ul><li>Vane test </li></ul></ul></ul><ul><ul><ul><li>Unconfined compression test </li></ul></ul></ul>
  11. 11. Ground Water Control <ul><li>Water can be classified by its relative position to or within the ground. </li></ul>
  12. 12. Ground Water Control <ul><li>Problems of water in the subsoil: </li></ul><ul><ul><li>A high water table could cause flooding during wet period. </li></ul></ul><ul><ul><li>Subsoil water can cause problems during excavation works by its natural tendency to flow into the voids created by the excavation activities. </li></ul></ul><ul><ul><li>It can cause an unacceptable humidity level around finished building and structures. </li></ul></ul>
  13. 13. Ground Water Control <ul><li>Control of ground water always referred to temporary and permanent exclusion. </li></ul><ul><ul><li>Temporary exclusion: lowering of the water table and within the economic depth range of 1500mm using subsoil drainage methods, for deeper treatment a pump or pumps are usually used. </li></ul></ul><ul><ul><li>Permanent exclusion: the insertion of an impermeable barrier to stop the flow of water within the ground. </li></ul></ul>
  14. 14. Ground Water Control
  15. 15. Ground Water Control <ul><li>Temporary exclusion </li></ul><ul><ul><li>Simple Sump Pumping </li></ul></ul><ul><ul><li>Jetted Sumps </li></ul></ul><ul><ul><li>Wellpoint Systems </li></ul></ul>
  16. 16. Ground Water Control <ul><li>Simple Sump Pumping </li></ul><ul><ul><li>Suitable for trench work and/or where small volume of water are involved. </li></ul></ul>
  17. 17. Ground Water Control
  18. 18. Ground Water Control <ul><li>Jetted Sumps </li></ul><ul><ul><li>Almost the same with simple sump methods of dewatering. </li></ul></ul><ul><ul><li>A borehole is formed in the subsoil by jetting a metal tube into the ground by means of pressurised water to a depth within the maximum suction lift of the extract pump. </li></ul></ul><ul><ul><li>The metal tube is withdrawn to leave a void for placing a disposable wellpoint and plastic suction pipe. </li></ul></ul><ul><ul><li>The area surrounding the pipe is filled with coarse sand as filtering media. </li></ul></ul>
  19. 19. Ground Water Control
  20. 20. Ground Water Control <ul><li>Wellpoint systems </li></ul><ul><ul><li>This is a method of lowering the water table to a position below the formation level to give a dry working area. </li></ul></ul><ul><ul><li>Jetting into the subsoil a series of wellpoints which are connected to a common header pipe which then connected to a vacuum pump. </li></ul></ul><ul><ul><li>Commonly use in trench excavation. </li></ul></ul><ul><ul><li>If the proposed formation level is below the suction lift capacity of the pump a multi-stage system can be employed. </li></ul></ul>
  21. 21. Ground Water Control
  22. 22. Ground Water Control
  23. 23. Ground Water Control
  24. 24. Ground Water Control <ul><li>Permanent exclusion </li></ul><ul><ul><li>Thin Grouted Membranes </li></ul></ul><ul><ul><li>Contiguous Piling </li></ul></ul><ul><ul><li>Diaphragm Wall </li></ul></ul><ul><ul><li>Precast Concrete Diaphragm Walls </li></ul></ul><ul><ul><li>Grouting Methods </li></ul></ul><ul><ul><li>Ground Freezing Techniques </li></ul></ul>
  25. 25. Ground Water Control <ul><li>Thin Grouted Membranes </li></ul><ul><ul><li>Work as permanent curtain or cut-off non structural walls or barriers inserted in the ground to enclose the proposed excavation area. </li></ul></ul><ul><ul><li>Suitable for silts and sands and can be installed rapidly but they must be adequately supported by earth on both sides. </li></ul></ul><ul><ul><li>The only limitation is the depth to which the formers can be driven and extracted. </li></ul></ul>
  26. 26. Ground Water Control
  27. 27. Ground Water Control <ul><li>Contiguous Piling </li></ul><ul><ul><li>Forms a permanent structural wall of interlocking bored piles. </li></ul></ul><ul><ul><li>Alternate piles are bored and cast by traditional methods after which the interlocking piles are bored using a special auger or cutter. </li></ul></ul><ul><ul><li>Suitable for most types of subsoil and has the main advantages of being economical on small and confined sites; capable of being formed close to existing foundations and can be installed with the minimum of vibration and noise. </li></ul></ul>
  28. 28. Ground Water Control <ul><li>Contiguous Piling </li></ul><ul><ul><li>To ensure a complete interlock of all piles over the entire length may be difficult therefore the exposed face of the piles is usually covered with a mesh or similar fabric and face with rendering or sprayed concrete. </li></ul></ul><ul><ul><li>Suitable for structures such as basements, road underpasses and underground car parks. </li></ul></ul>
  29. 29. Ground Water Control
  30. 30. Ground Water Control <ul><li>Diaphragm Wall </li></ul><ul><ul><li>Are structural concrete walls which can be cast in-situ or using pre-cast concrete methods. </li></ul></ul><ul><ul><li>Suitable for most subsoil and their installation generates only a small amount of vibration and noise. </li></ul></ul><ul><ul><li>The high cost of these walls makes them uneconomic unless they can be incorporated into the finished structure. </li></ul></ul><ul><ul><li>Normally use for basements, underground carparks and similar structures. </li></ul></ul>
  31. 31. Ground Water Control
  32. 32. Ground Water Control <ul><li>Pre-cast Concrete Diaphragm Wall </li></ul><ul><ul><li>Have some applications with in-situ concrete diaphragm walls. </li></ul></ul><ul><ul><li>Lack in design flexibility. </li></ul></ul><ul><ul><li>The panel or post panel units are installed in a trench filled with a special mixture of bentonite and cement with a retarder to control the setting time. </li></ul></ul><ul><ul><li>This mixtures ensures that the joints between the wall components are effectively sealed. </li></ul></ul><ul><ul><li>To provide stability, the panels of posts are tied to the retained earth with ground anchors. </li></ul></ul>
  33. 33. Ground Water Control
  34. 34. Ground Water Control <ul><li>Grouting Methods </li></ul><ul><ul><li>Are used to form a curtain or cut-off wall in high permeability soils where pumping methods could be uneconomic. </li></ul></ul><ul><ul><li>The curtain walls formed by grouting methods are non-structural therefore adequate earth support will be required and in some cases this will be a distance of at least 4m from the face of proposed excavation. </li></ul></ul>
  35. 35. Ground Water Control <ul><li>Grouting Methods </li></ul><ul><ul><li>Grout mixtures are injected into the soil by pumping the grout at high pressure through special injection pipes inserted in the ground. </li></ul></ul><ul><ul><li>The pattern and spacing of the injection pipes will depend on the grout type and soil conditions. </li></ul></ul><ul><ul><li>Grout types: </li></ul></ul><ul><ul><ul><li>Cement grouts </li></ul></ul></ul><ul><ul><ul><li>Chemical grouts </li></ul></ul></ul><ul><ul><ul><li>Resin grouts </li></ul></ul></ul>
  36. 36. Ground Water Control
  37. 37. Ground Water Control <ul><li>Ground Freezing Techniques </li></ul><ul><ul><li>Suitable for all types of saturated soils and rock and for soils with a moisture content in excess of 8% of the voids. </li></ul></ul><ul><ul><li>The basic principle is to insert into the ground a series of freezing tubes to form an ice wall thus creating an impermeable barrier. </li></ul></ul><ul><ul><li>Takes time to develop and the initial costs are high. </li></ul></ul>
  38. 38. Ground Water Control <ul><li>Ground Freezing Techniques </li></ul><ul><ul><li>The freezing tubes can be installed vertically for conventional excavations and horizontally for tunneling works. </li></ul></ul><ul><ul><li>Normally using magnesium chloride and calcium chloride with a temperature of -15 to -25 degree Celsius which takes 10 to 17 days to form an ice wall 1m thick. </li></ul></ul><ul><ul><li>Liquid nitrogen could be used as the freezing medium to reduce the initial freezing period if the extra cost can be justified. </li></ul></ul>
  39. 39. Ground Water Control
  40. 40. Preliminaries Works <ul><li>What is preliminaries work? </li></ul><ul><li>The reason of having preliminaries works? </li></ul><ul><li>Is there any difference between preliminaries items for different projects? Why? </li></ul><ul><li>Example of preliminaries items that is needed for a project. </li></ul>