Experimental Study Of Set-up Mechanisms Of Bearing Capacity Of Jacked-in Piles

Soil/pile set-up, which is time-dependent increase in jacked-in pile capacity, is an important problem in geotechnical engineering. If it were possible to incorporate the effects of set-up during design, it may be possible to reduce building cost of projects. Based on the results of the experimental tests on ISO sand and silty clay with GDS system, the factors affecting the long-term bearing capacity are analyzed and some useful conclusions are gained as follows.1) A series of drained and undrained Strain-holding tests were implemented on ISO sand with GDS by means of respective-loading manner. Based on the analysis of the results under different drained condition, a conclusion is reached that the soil around the pile in sand experiences the process of consolidation and shearing creep, not stress relaxation.2) The same test procedure is used for silty clay under drained condition, furthermore, some samples were reloaded after axial stress stabilizing. The analysis shows the soil around the pile experiences the process of primary consolidation and secondary consolidation, and both the shear strength and the initial shear modulus increase after consolidation and secondary consolidation.3) The results of tests on ISO sand and silty clay are analyzed and compared, and it shows that: for sand, short-term setup of bearing capacity of the pile depends on the consolidation of surrounding soil, and long-term setup depends on shear swelling, which causes the radial stress to increase around the pile; for the clay, the setup of bearing capacity of the pile depends on the consolidation, and secondary consolidation has not remarkable effect on soil/pile set-up.