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某高层建筑建造于岩溶场地,采用刚性桩复合地基。在现场开展了大型坑下综合性原位试验,包括多项载荷试验、桩与土的应力测试以及沉降观测等。运用BOTDA分布式光纤技术,获得复合地基桩身应力及桩侧摩阻力连续分布曲线。基于试验数据,对复合地基的荷载传递机制、荷载分担变化与发展规律、桩与土承载力发挥状况等进行了分析,研究了土层注浆和桩底后注浆对复合地基承载力与应力分布的影响。研究表明:增强体采用非挤土置换成桩工艺,对桩间土具有加固效果;桩底后注浆对复合地基的加固效果主要体现在加载后期的较高荷载水平下;土层注浆在提高桩间土和复合地基承载力的同时,降低了桩、土相对刚度,总体上有利于发挥土的承载作用;土层注浆对桩侧正、负摩阻力发挥均具有作用,可减少荷载经桩传递产生的下卧层附加应力,有利于下伏溶洞的安全。根据研究结果,给出了采用土层注浆时复合地基承载力发挥系数的建议值。
A high-rise building built in karst sites, the use of rigid pile composite foundation. A large-scale underground comprehensive in-situ test was carried out at the site, including a number of load tests, stress testing of piles and soil, and settlement observation. Using BOTDA distributed optical fiber technology, the continuous distribution curve of pile foundation stress and pile friction is obtained. Based on the experimental data, the load transfer mechanism, load sharing and development of composite foundation and the status of pile-soil bearing capacity are analyzed. The influences of grouting and pile grouting on the bearing capacity and stress of composite foundation are studied. The impact of distribution. The results show that the reinforcements are reinforced by non-compacted soil replacement pile, which has the effect of reinforcing the soil between piles. The reinforcing effect of post-pile grouting on the composite foundation is mainly reflected in the higher load level in the later stage of loading. While increasing the bearing capacity of soil and composite foundation between piles, while reducing the relative stiffness of piles and soil, it is conducive to the bearing capacity of soil as a whole; soil grouting has a positive effect on positive and negative frictional resistance of piles and can reduce the load Additional stress generated by the pile under the sub-layer, is conducive to the safety of the underlying karst cave. According to the research results, the recommended value of the coefficient of bearing capacity of the composite foundation when using soil grouting is given.