带承台高喷插芯组合单桩荷载传递特性试验研究

 高喷插芯组合桩(JPP)是由高压旋喷桩和预应力混凝土芯桩构成的一种新型组合桩。为了对带承台单桩荷载传递特性有更深入的认识，以自行开发的大型桩基试验模型槽为依托，对带承台单桩进行静载试验。通过埋设在JPP中的监测仪器和承台下传感器得到如下荷载传递特性：与不带承台JPP单桩相比，带承台单桩承载力显著提高，承台可以承担较大比例的荷载；桩土应力比为20～100，且桩顶处桩土应力比基本维持在22左右，为承台与桩截面面积比的2倍；承台的存在限制了桩土相对位移，摩阻力不易发挥；承台对桩侧摩阻力有“削弱”作用，特别是对上部摩阻力，对桩端阻力有“增强”作用，并且与不带承台单桩相比，达到极限摩阻力所需位移增大。这些成果对JPP与承台共同作用特性研究具有一定的意义。

EXPERIMENTAL RESEARCH ON LOAD TRANSFER BEHAVIORS OF SINGLE JET GROUTING SOIL-CEMENT-PILE STRENGTHENED PILE WITH CAP

Jet grouting(JG) soil-cement-pile strengthened pile(JPP) is a new kind of composite pile composed of high-pressure jet grouting pile and prestressed core pile. In order to make a further research on load transfer mechanism of single JPP with cap，the large-scale model test has been done on the self-developed foundation model slot. With the prearranged instrument in JPP and soil under cap，the following main characteristics of load transfer are drawn. (1) Compared with single JPP，JPP with cap has larger bearing capacity，and the ratio of load carried by cap is higher. (2) The relative displacement between JPP and soil is controlled by cap，which leads to the fact that the friction resistance does not exert sufficiently. (3) Pile-soil stress ratio of JPP with cap is between 20 and 100，and the ratio on the pile top is around 22，about twice the ratio of cap area and pile area. (4) The cap of JPP makes friction resistance decrease and tip resistance increase；and the displacement of the ultimate resistance is larger than that of JPP without cap. These results are beneficial for cap-JPP-soil interaction research.