变刚度桩筏基础变形特性试验研究

分别以天然地基筏板和4组变刚度桩筏基础模型对比试验为基础，分析基桩平面布置、几何尺寸与基础沉降的关系，从而为桩筏基础变刚度调平概念设计提供试验依据。试验研究表明：与上部结构共同作用的桩筏基础，总体上其沉降分布表现为中心区域沉降较大而边角位置沉降较小；筏下均匀布桩较之天然地基，基础沉降量的最大值大约减少70%；基础中心区域桩长增加1倍或者桩数增加1／3，沉降量的最大值约减少50%；上部结构与核心筒下局部加大基桩几何尺寸和适当增加桩数能够有效地减少沉降量的最大值以及沉降差，从而达到调平的效果；筏下布桩有助于减少基础周边的地表沉降，可使其影响局限于1／4基础宽度范围之内。图11表3参12

Experimental study on deformation behavior of piled raft foundation

Based on experimental study on raft foundations which were located on a natural subsoil and four pile groups respectively, the relationships between the base settlement and the plan layout or the geometric size of the pipes were analyzed in order to provide the experimental basis for the stiffness-balanced conceptual design of the piled raft foundation. The results show that the settlement distribution of the piled raft foundation with superstructure exhibits the feature that the settlement of the center is larger than that of the corner. The maximum settlement of the raft foundation located on the uniform pile reduces about 70% than that located on the natural base, however, if the length of the pile is doubled or the number of the pile is increased by 1/3 in the central region of the raft foundation，the maximum settlement can reduce about 50%. The maximum and the differential settlement of the foundation can be reduced effectively by means of increasing the geometric size or the total number of the pipes under the superstructure which includes the core-tube structure. The raft foundation with the piles can reduced the surface settlement of the ground around the building，and the influenced region is limited within only an extension of 1/4 width of the foundation.