AGS meeting on revetment walls for unsaturated clay. Clay pit at Thebarton : sandy clay which the design using saturated clay and the friction angle from CIU Triaxial Testing. Installing soil nails for the Bakewell Underpass. Underpass Millswood consists of 100mm thick which it is cheaper. Project aims when a design approach need to consider the construction method need to be thick of safety. Field investigation method and lab testing needed to provide input to design.
Mr. John Woodburn who is an expert in unsaturated soil presented the basic stability analysis, background information about soil suction and design suction profiles. Typical underpass like North South Corridor consists of 34m wide and 4m depth of underpass. Australia Standard 4678, 2002 recognizes a class of structure known as revetment wall which utilizes the inherent strength of the soil mass with vertical 70 degrees. Revetment walls relatively shallow sloping cuts in unsaturated soil are stable and not required retaining wall. It can protect the soil surface from wetting and drying. Maximum height of vertical cuts is 4c/γ for cohesive soil. Increase in height helps to stable slope with deceasing face angle. Design consideration row needed to include investigation range of soil and pressure. Large trees will cause shrinkage and foundation problems.
Soil suction at in situ moisture content are normal missing. To argument field test can increase confidence. To characterize the soil can use the Sieve analysis and Atterberg Limits Test. Saturation or equilibration can take weeks, not overnight otherwise results are unreliable in CIU test. Soil strength characterization involves measurement of shear strength and total suction. Soil is wetted by applying hydraulics gradient across and is confined state.
Two contributing factor of soil suction – Governing Freland’s for US which assume the pore water pressure is zero. For dry Hindmarsh clay undrained values Cu = 0 kPa and ϕu 38 degrees. Two broad methods of revetment analysis are limit equilibrium method to seach for lowest factor of safety(FOS) and Finite Element method used for modeling suction profiles. It uses matric suction in kPa and need to convert pF in to kPa.
For excavation or construction need to know likehood of perched watertables, pockets of loose dry sands, saturated sands in old stream channels and blocky clays. Feasibility as for long deep excavation consists of range of soil present. Stage excavation need to be carried out quickly and safely without the need of ground support. Verification of ground condition and implementation of drainage consideration design of revetment wall should be flexible with articulation, drainage required behind the wall to ensure that saturation does not occur. Advantages of precast panel construction over the 1st and 2nd methods as work can proceed rapidly. Final trimming can be made before. Precast concrete for revetment wall would allow rapid and much cheaper construction of underpass.
Mr. John Woodburn who is an expert in unsaturated soil presented the basic stability analysis, background information about soil suction and design suction profiles. Typical underpass like North South Corridor consists of 34m wide and 4m depth of underpass. Australia Standard 4678, 2002 recognizes a class of structure known as revetment wall which utilizes the inherent strength of the soil mass with vertical 70 degrees. Revetment walls relatively shallow sloping cuts in unsaturated soil are stable and not required retaining wall. It can protect the soil surface from wetting and drying. Maximum height of vertical cuts is 4c/γ for cohesive soil. Increase in height helps to stable slope with deceasing face angle. Design consideration row needed to include investigation range of soil and pressure. Large trees will cause shrinkage and foundation problems.
Soil suction at in situ moisture content are normal missing. To argument field test can increase confidence. To characterize the soil can use the Sieve analysis and Atterberg Limits Test. Saturation or equilibration can take weeks, not overnight otherwise results are unreliable in CIU test. Soil strength characterization involves measurement of shear strength and total suction. Soil is wetted by applying hydraulics gradient across and is confined state.
Two contributing factor of soil suction – Governing Freland’s for US which assume the pore water pressure is zero. For dry Hindmarsh clay undrained values Cu = 0 kPa and ϕu 38 degrees. Two broad methods of revetment analysis are limit equilibrium method to seach for lowest factor of safety(FOS) and Finite Element method used for modeling suction profiles. It uses matric suction in kPa and need to convert pF in to kPa.
For excavation or construction need to know likehood of perched watertables, pockets of loose dry sands, saturated sands in old stream channels and blocky clays. Feasibility as for long deep excavation consists of range of soil present. Stage excavation need to be carried out quickly and safely without the need of ground support. Verification of ground condition and implementation of drainage consideration design of revetment wall should be flexible with articulation, drainage required behind the wall to ensure that saturation does not occur. Advantages of precast panel construction over the 1st and 2nd methods as work can proceed rapidly. Final trimming can be made before. Precast concrete for revetment wall would allow rapid and much cheaper construction of underpass.
A little bit confused esp the first para of notes.
ReplyDelete"For dry Hindmarsh clay undrained values Cu = 0 kPa and ϕu 38 degrees." doesn't seem right.
2.7 ex 4