中文摘要：

基于三剪统一强度准则和非饱和土双应力状态变量抗剪强度,考虑中间主应力效应、材料拉压不等特性和强度准则差异的影响,建立了非饱和土抗剪强度三剪统一解,并在此基础上推导了非饱和土条形地基太沙基极限承载力的计算公式。通过可行性分析及算例论证,验证了所推公式的正确性,探讨了中间主应力效应、强度准则、基质吸力、有效内摩擦角和有效黏聚力等参数对非饱和土条形地基极限承载力的影响规律。研究结果表明：中间主应力效应和强度准则对非饱和土条形地基太沙基极限承载力具有显著影响,中间主应力效应越显著,极限承载力越高,说明考虑中间主应力效应可以更加充分发挥材料的强度潜能,也说明强度准则差异对地基极限承载力的预测具有重要作用。基质吸力对非饱和土条形地基太沙基极限承载力具有双重影响：在低基质吸力范围内,极限承载力随基质吸力的增大线性提高;当基质吸力增大到进气值时,极限承载力达到峰值;在高基质吸力范围内,极限承载力随基质吸力的增大逐渐降低,最终趋于稳定。非饱和土条形地基太沙基极限承载力随有效内摩擦角和有效黏聚力的增大显著提高。非饱和土太沙基极限承载力三剪统一解包含了多种屈服准则下地基承载力的计算公式,具有较广泛的适用性,可为实际工程应用提供参考。

英文摘要：

Based on the triple-shear unified strength criterion and shear strength of unsaturated soil in terms of two state stress variables, a triple-shear unified solution of shear strength for unsaturated soil is obtained with considering the effects of the intermediate principal stress, strength disparity of materials and strength criterion. A formulation of Terzaghi’s ultimate bearing capacity for unsaturated soil foundation is developed, and validated through the feasibility analysis and example demonstration. In addition, the influences of various factors, including intermediate principal stress effect, strength criterion, matric suction, effective internal frictional angle and effective cohesion, are discussed on the ultimate bearing capacity of unsaturated soil foundation. The results show that the intermediate principal stress and strength criterion have significant impact on the ultimate bearing capacity, namely, the more remarkable the intermediate principal stress effect, the higher the ultimate bearing capacity is. It is also shown that the consideration of intermediate principal stress can fully mobilize the soil strength and the strength criterion plays an important role in predicting the ultimate bearing capacity. The matric suction has dual effects on the Terzaghi ultimate bearing capacity of strip foundation. In low matric suction region, the ultimate bearing capacity increases linearly with the increase of matric suction and attains its maximum when the matric suction reaches the air-entry value. In high matric suction region, the ultimate bearing capacity decreases gradually and finally maintains constant. Moreover, the Terzaghi ultimate bearing capacity increases dramatically as the effective internal frictional angle and effective cohesion increase.