复合地基中垫层作用机理

来源期刊：中南大学学报(自然科学版)2001年第6期

论文作者：刘杰 张可能

文章页码：568 - 572

关键词：复合地基;垫层;协调方程;应力比

Key words：the composite foundation; the cushion; correspondence equation; stress ratio

摘    要：以土力学和弹性理论为基础推导出了刚性、半刚性桩复合地基的竖向变形协调方程,从理论上建立了垫层厚度及压缩模量对刚性、半刚性桩复合地基性质和形状的影响的数学表达式.在此基础上,得出了不同的垫层厚度及垫层模量对桩土应力比、桩身最大应力位置、桩身最大应力、桩土荷载传递的影响.研究结果表明:增大垫层厚度及降低垫层模量都能缓解桩顶应力集中程度,但等沉面位置下降,桩端应力增大,因此,靠过多地提高垫层厚度和降低垫层模量来获得较低的桩土应力比不可取;垫层的最佳厚度为0.2~0.5 m ,垫层的最佳压缩模量为30~100 MPa,这与目前工程上常用的垫层厚度和垫层模量相符;利用该方法可对刚性、半刚性桩复合地基进行优化设计.

Abstract: Based on soil mechanics and elastic theory, the correspondence equation of the vertical deformation of the composite foundation of the stiff pile and the half stiff pile is derived in this paper. The mathematics formula of the cushion thickness and compression modulus of influence on the composite foundation of the stiff and the half stiff pile is derived. Based on it, influence of the different cushion thickness and compression modulus on the stress ratio of pile and soil, on the location of the greatest stress and the greatest stress in pile, on the load transfer in pile and soil is determined. The conclusion of relaxing stress concentration on the pile top by improving the cushion thickness and lowering the cushion modulus is obtained, but the location of the equal settlement section is lowered. On the contrary the stress of the pile end is increased. So it isn′t useful to excessively increase the thickness and lower the cushion modulus to acquire lower stress ratio of pile and soil. Synthesis analysis indicates that the best cushion thickness is 0.2~0.5 m and the best compression modulus of the cushion is 30~100MPa. This cushion thickness corresponds with the thickness used in engineering. The optimized design on the composite foundation of the stiff and half stiff pile by the cushion can be performed with this method.