非饱和土条形地基梅耶霍夫极限承载力统一解

Unified solution of Meyerhof’s ultimate bearing capacity for strip foundation resting on unsaturated soils

基于非饱和土的抗剪强度统一解,综合考虑中间主应力、基质吸力和强度非线性,建立非饱和土条形地基的梅耶霍夫极限承载力统一解,对比文献滑移线法解答、上限法解答验证所得统一解的正确性和适用性,讨论与太沙基极限承载力的差异及基底粗糙程度效应,并得出中间主应力、高/低基质吸力以及有效强度参数的影响规律。研究结果表明：太沙基极限承载力将旁侧土的抗剪强度简化为均布荷载,夸大了旁侧土的真实作用,计算结果偏大;基底粗糙程度对承载力系数的确定起关键性作用,梅耶霍夫极限承载力随中间主应力效应的增大而显著增加,不考虑中间主应力影响的Mohr-Coulomb解答过于保守;基质吸力具有双重影响,即在低吸力范围内极限承载力线性增加,而在高吸力范围内却逐渐减小并趋于稳定,这是由非饱和土的强度非线性造成的;有效强度参数的影响亦很重要,且有效内摩擦角较有效黏聚力的影响更明显。由于考虑了中间主应力效应、非饱和特性与旁侧土抗剪强度等工程实际情况,本文结果可为地基优化设计与施工提供有益的参考。

Based on the unified solution of shear strength for unsaturated soils, a unified solution of Meyerhof＇s ultimate bearing capacity for strip foundation is obtained by considering the effects of intermediate principal stress, matric suction and strength nonlinearity. The validity and applicability of the obtained unified solution are demonstrated by comprising it with the results of the slip-line theory and upper-bound theory available in literatures. The differences of the ultimate bearing capacity between the Terzaghi＇s theory and Meyerhof＇s theory and the roughness effect of foundation base are discussed. The influences of the intermediate principal stress, high/low matric suction and effective strength parameters are investigated. The findings show that the Terzaghi＇s ultimate bearing capacity simplifies the shear strength of lateral soils as uniform load, which exaggerates the real effect of lateral soils and leads to a larger result. The roughness of foundation base is critical for determining the bearing capacity factors. Meyerhof＇s ultimate bearing capacity increases significantly with the intermediate principal stress effect, and the results of Mohr-Coulomb criterion are too conservative due to no consideration of the intermediate principal stress. The matric suction has a dual-effect： the ultimate bearing capacity increases linearly in the low suction region, meanwhile it gradually decreases and eventually stabilizes in the high suction region, which is caused by the nonlinear strength of unsaturated soils. The effects of the effective strength parameters are also important, and furthermore the effect of the effective internal friction angle is more obvious than that of the effective cohesion. Due to considering many practical engineering conditions, such as the intermediate principal stress effect, unsaturated characteristics as well as shear strength of lateral soils, this study can provide useful references for the optimization of foundation design and construction.