膨胀力在非饱和土强度理论中的作用

The Role of Swelling Pressure in the Shear Strength Theory of Unsaturated Soils

回顾了Ｂｉｓｈｏｐ和Ｆｒｅｄｌｕｎｄ提出的两种用吸力（ｕａ－ｕｗ）计算吸附强度的理论公式，提出了非饱和土抗剪强度是由以下三个部分组成：①真凝聚力ｃ；②外力产生的摩擦强度（σ－ｕａ）ｔｇφ；③吸力所产生的内摩擦强度（吸附强度）τｓ。并对三种理论公式及吸附强度计算式进行了总结对比，指出Ｂｉｓｈｏｐ和Ｆｒｅｄｌｕｎｄ公式因其吸力及参数均复杂难以测定，至今尚未能在工程实际中广泛应用，而本文公式因膨胀力ｐｓ和参数ｍ测定技术简便易行，可为非饱和土抗剪强度的研究工作提供一条新的探索与发展途径。

The shear strength of unsaturated soils is composed of 3 parts:(1) the true cohesion, c;(2)the frictional strength due to external forces, (σ-u)tgφ; and (3) the internal friction produced by suction. The third component is called “suctional strength” and denoted by the symbol τ s in this paper. Although the shear strength theory of unsaturated soils has been established by Bishop and Fredlund in 1960 and 1978 respectively, it has rarely been adopted in engineering practice because of the difficulty in measuring suction and related parameters. It was discovered that the swelling pressure p s of unsaturated soils measured under constant volume condition might be in linear relationship with the suctional strength τ s. Some investigations in early 90′s further proved the above discovery and are reported is the paper. Since the measurement of swelling pressure is much more easier than that of suction, it may provide a new and convienent method of approach to this problem.