软土地基中组合桩水平受荷作用下的试验研究

组合桩为预应力混凝土桩插入水泥搅拌桩中而形成的新桩，为探讨该桩在水平荷载在用下的承载力和破坏模式，通过3根14.0 m长组合桩的水平载荷试验，实测得到该桩在水平荷载作用下桩与土共同作用下的工作性状和破坏特征，分析了组合桩受水平力作用时的临界和极限荷载、破坏模式、地基土的水平抗力比例系数以及桩帽对组合桩抗水平力的有利作用。为合理地评价组合桩的水平承载力，探讨组合桩在水平荷载作用下的计算方法：临界荷载法和转折点法，并给出计算公式。试验和分析结果表明：组合桩具有较好地抵抗水平荷载的能力，有桩帽的组合桩水平受荷性状优于无桩帽的组合桩，桩帽使组合桩由水泥桩和外侧的水泥壳之间相互分开的破坏模式变为外侧的水泥土和土之间分开的模式，保证组合桩在水平荷载下的完整性，用转折点法计算组合桩的水平承载力更为合理。

TEST OF COMPOSITE PILES UNDER LATERAL LOADING IN SOFT GROUND

A new-style composite pile is obtained by inserting a prestressed concrete pile into a cement-mixing pile To study the bearing capacity and failure mode of the composite pile under lateral loading, the lateral loading tests of two composite piles with/without pile cap are carried out and the failure modes and property of interaction of pile and soil are obtained. As a new-style pile, its key characters are analyzed, such as critical load, limit load, lateral deformation, failure modes of two composite piles with/without pile cap, influence of lateral resisting-force coefficient of soil and pile cap on lateral bearing capacity and failure mode. To reasonably evaluate the test results, the limit load and deformation are also analyzed. Test and analysis results show that the pile cap plays an important role in resisting lateral load and the property of resisting lateral force of the composite pile with pile cap is higher than that of the composite pile without pile cap. Composite piles with pile cap have better lateral bearing capacity. Pile cap changes the failure mode between prestressed concrete pile and cement soil into the failure mode between cement soil and soil. To calculate the lateral bearing capacity of composite piles, the calculation formulae of lateral bearing capacity based on critical method and turning point method are studied and the turning point method shows more reasonable and operational than the critical method in application.