砂土地基中五个扩展基础加载试验成果的分析

Analysis of Loading Test Results of Five Spread Footings in Sand

采用修正弦线模量法对Briaud和Gibbens所做的一系列砂土地基中的基础加载试验成果进行比较分析.首先对不同基础加载试验曲线进行归一化处理,获得不同基础荷载与相对沉降的归一化曲线,该曲线与计算曲线相吻合;其次,对基础加载后分层土随深度变化的应变规律进行总结,修正弦线模量法计算结果除基底附近浅部土层外,其余土层大致吻合,其应变值随深度增加而减少,基底附近浅部土层例外的原因在于基底粗糙度对地基的侧向变形.分析结果表明:修正弦线模量是一种地基的等效模量,采用该模量按分层总和法预测地基在各级荷载下的总沉降比较可靠,但预测每一分层土的沉降还不够准确,原因在于修正模量法未考虑基础底面粗糙度对地基土侧向变形的约束作用.

Results of a series of load tests performed by Briaud and Gibbens （1993） on five squared spread footings in sand are analyzed and compared with correction chord modulus method. Firstly, different loading test curves of spread footings is unified, and their unified curve of pressure versus settlement over width （S/ B） is obtained, which can be predicted accurately with correction chord modulus method. Secondly, the natural laws in strain with depth is summarized. It is indicated that this is consistent with the theory of correction chord modulus except close to the bottom of the footing, where the strain decreases due to the lateral confinement brought about by the roughness of the footing base. It seems that the correction chord modulus is an e quivalent modulus of foundation; and the modulus can be used by stratified summation method to predict total settlement at all levels of the foundation load reliably; but each layer of soil forecasting settlement is not accurate enough; the reason is that the confining action of basic bottom roughness to the lateral deformation of the foundation soil is not considered for the correction chord modulus method.