混凝土芯水泥土搅拌桩复合地基现场试验研究

混凝土芯水泥土搅拌桩是在水泥土搅拌桩外壳施工完成后插入预制混凝土芯所形成的一种新型复合桩。现有研究对混凝土芯水泥土搅拌桩复合地基的承载力机理讨论很少。为完善混凝土芯水泥土搅拌桩复合地基承载力理论,依托南京绕越高速东北段软基处理工程,通过埋设传感元件,借助复合地基载荷板试验和静力触探试验,分析了其承载力机理。试验结果表明:混凝土芯水泥土搅拌桩的地基加固效果要优于同直径同桩长的水泥土搅拌桩;混凝土芯的插入,有效增大了混凝土芯水泥土搅拌桩的竖向抗压强度;混凝土芯与水泥土搅拌桩外壳之间能有效传递剪应力,且水泥土搅拌桩外壳的大表面积保证了桩土间不会发生剪切破坏;相同的上部荷载下,混凝土芯水泥土搅拌桩复合地基的桩土应力比要大于水泥土搅拌桩复合地基;混凝土芯水泥土搅拌桩施工对桩周土体有一定的挤密加固效果。

Field Test of Concrete-cored DCM Pile Composite Foundation

The concrete-cored DCM pile is a new kind of composite pile created by inserting precast core pile into the deep cement mixing (DCM) column socket. Till now, few researches discuss the working characteristics of composite foundation by the way of concrete-cored DCM pile. By combining sensing elements, plate load tests on composite foundation and cone penetration tests were conducted in Nanjing Surrounding expressway to discuss the bearing mechanism of concrete-cored DCM pile composite ground. Test results show that:With the same diameter and length, the reinforcement effect of concrete-cored DCM pile is better than that of DCM column. Due to the insert of precast core pile, the vertical compression strength of concrete-cored DCM pile is high. The shear stress can be transferred effectively between precast core pile and DCM column socket. The failure of the surrounding soil due to high shear stress transferring from the pile can be avoided according to the large surface of DCM column socket. Under the same upper load, the pile-soil stress ratio of concrete-cored DCM pile composite foundation is larger than that of DCM column composite foundation. The mechanical properties of surrounding soil are influenced largely by the construction of concrete-cored DCM piles.