Experimental study of long-short piles composite foundation in deep soft soils

For researching reinforcement effect and bearing characteristics of long-short cement-soil piles composite foundation in deep soft soils,the test in situ on the bearing characteristics of long-short cement-soil piles composite ground in deep soft soils are carried out.The stresses of long piles,short piles and soil are measured;and pile-soil stress ratio of composite ground with cement-soil long-short piles and its variation with the load in deep soils are also studied.According to pile-soil stress ratio,it has been found that stress ratio increases at first and then decreases and finally tend to stability.It is revealed that the sequence of primary piles and secondary pile are changed after reaching critical load P_c.Based on the result of static load test,computational formulas for bearing capacity characteristic value and bearing capacity coefficient of cement-soil long-short piles composite foundation which have thought of load level are developed in this paper.Result indicates that the value of β ranges 0.778~0.838,β₂ is 0.945~0.971.It is suggested that when s/b is 0.001 48~0.002 04 the value of bearing capasity is bearing capacity characteristics of cement-soil long-short piles composite foundation.