Study On The Influence Of Mudcake On Engineering Behavior Of Bored Pile

Through laboratory tests on mudcake and middle soil of bored piles in silt soil,clay and silt in Hangzhou,the influence of mudcake on shaft friction and the difference between mudcake and middle soil of bored piles have been studied.In addition,by using laboratory tests on mixed mud with cement grout,the improved effect on mudcake with cement grout is analyzed.Researching result shows that compared with middle soil,mudcake moisture content increases 6% 16%,void ratio increases 5%¹6%,compressibility reduces 6%²4%,shear strength and friction reduce separately 7%²5% and 14% ³0%.Mudcake is weaker than middle soil and its (σ₁- σ₃)_f reduces 9.2% 17% .Mudcake becomes a weak layer between pileand soil and reduces the shaft friction of piles.As the percent of cement grout increase from 10% to 40%,compressibility increase from 1.86MPa to 8.96MPa,shear strength and friction increase separately from 0.5° to 19°and from 2kPa to 18kPa.Analyze the settlement calculation of boled piles with mudcake.Based on shear displacement method,the analytical expressions for different boundary conditions for axial load-settlement of pile with mudcake were derived.And it is also extended to stratification soil foundation. Analyze the bearing capacity calculation of piles thinking about mudcake and coarse bore.And it is proved with an actual engineering.By using the great FEM programme ,this paper analyses the charaters of bored pile with mudcake in piles of different lenth. And analyses the different charaters of bored pile with different thickness mudcake and different elastic modulus.In addition,through pile models with sediment in pile tip, the influence of sediment in pile tip on the bearing capacity of the piles is analysed.Researching result shows that the shaft friction and bearing capacity of piles is reduced as the thickness of mudcake increases and the elastic modulus of mudcake reduced.And the pile will glide ahead of schedule.The bearing capacity and settlement of the piles with sediment in pile tip is reduced as the thickness of sediment increases.