采用修正割线模量法分析地基的非线性沉降

提出了一种考虑时间因素的地基非线性沉降计算新方法，即修正割线模量法．该方法的计算原理是利用反馈修正技术依据地基载荷试验曲线反求各级荷载下地基土不同附加应力水平区段的修正割线模量，附加应力计算采用Boussinesq弹性理论解，采用分层总和法计算地基沉降．采用修正割线模量法对Briaud和Gibbens（1993）所做的一系列砂土地基中的基础加载试验成果进行分析．通过对不同基础加载试验曲线进行归一化处理，获得不同尺寸基础的荷载与相对沉降的归一化曲线，该曲线与计算曲线相吻合；采用修正割线模量法计算得到的不同尺寸基础对应于沉降25mm及150mm的荷载Q25及Q150与实测结果的误差在10％以内，根据南侧及北侧3m基础30min加载试验确定的蠕变指数m分别为0．036和0．030，计算得到2014年（20年后）2个3m基础所发生的总沉降分别为39．6mm和36．7mm．

Nonlinear Analysis of Foundation Settlement by Modified Secant Modulus Method

A new technique namely modified secant modulus method（MSMM）considering time factor for non- linear settlement computation of foundation is proposed. The principle of MSMM is using correction technique of reverse solution to solve modified secant modulus （MSM） of foundation under different additional stress levels by load-settlement test curve; and the additional stress calculation using Boussinesq solution of elastic- ity theory, then layer wise summation method is adopted to calculate the total settlement of foundation. A se- ries of loading test results of footings performed by Briaud and Gibbens （1993） on sand foundation are ana- lyzed by MSMM. Normalized settlement curves over width versus pressure for all footings can be obtained by normalization processing; and the calculation curve by MSMM agrees well with the normalization curves; The loads of Qz5 and Q150 corresponding to the settlements of 25mm and 150mm respectively of different size foot- ings are calculated; and the errors of them are within 10% compared with testing results; and the creep expo- nent of south and north footing for 30 minutes load test was 0. 036 and 0. 030; then the calculated total settle- ment in 2014 （ 20 years later） is 39.6 and 36.7mm respectively.