确定地基承载力的新方法

New method for determination of bearing capacity of soil foundation

地基承载力的合理确定对地基设计是最重要的一个内容。现场原位压板试验被认为是确定地基承载力最可靠的方法。但实际基础的地基承载力不仅与土性有关,还与基础的尺寸、埋深和沉降要求有关,压板试验的尺寸不是实际基础的尺寸,如何由压板试验合理地确定实际基础的地基承载力是一个还没有很好解决的问题。提出一个新的解决方法,即由压板试验反算地基的强度参数和变形指标,然后用这些参数对具体基础采用切线模量法计算基础的荷载和沉降关系的p–s曲线,再根据上部结构对基础的沉降要求和地基强度安全系数要求的双控原则,由p–s曲线确定满足沉降和强度要求的地基承载力,而不是直接由压板载荷试验曲线来确定地基承载力,这样可以更好地考虑基础的尺寸效应。通过案例进行了说明,并与现行的规范方法进行了比较,说明了新方法的合理性。

Reasonable determination of bearing capacity of foundation is the most important part of foundation design.The in-situ plate loading test is the most reliable method to determine the bearing capacity.However,the actual bearing capacity relates to not only soil property but also the size,buried depth and settlement requirement of the foundation.The size of the plate in the plate loading test is not the same as that of actual foundation,and how to determine the bearing capacity of the actual foundation by the plate loading test reasonably is not yet addressed.Thus,a new solution method is proposed in this paper.That is,the strength and deformation parameters are back-computed by the plate loading test.Then,based on those parameters,the tangent modulus method is employed to compute the load- settlement curve(p–s curve) of the foundation.Finally,according to the double controlling principles,the settlement requirement and strength safety factor requirement of the foundation,the bearing capacity of the foundation is determined by the p–s curve.The bearing capacity meets both settlement and strength requirements of the foundation.An example is adopted to illustrate the proposed method,and results are compared with those by the methods of the current codes of China to prove the rationality of this new method.