高应力粒状土中球形孔的扩张问题

考虑粒状土在高应力下的应力－尖变－体变关系和非线性强度特性，依据扩张过程中的能量守恒和体变平衡原理，给出扩极限压力的解答，用于估算临界深度以下静力触探或桩尖的贯入阻力。分析表明，扩孔极限压力取决于粒状土的应力－应变－体变关系和强度特性，与上覆土压力在大小无关。计算结果表明，考虑曲线型强度包线将减小扩孔极限压力，与中密砂土的静力触探贯入阻力经验值对比，初步证实了该理论的正确性。

PROBLEM OF SPHERICAL CAVITY EXPANSION IN GRANULAR SOIL UNDER HIGH STRESSES

The stress-strain-volume change relationships and nonlinear strength behaviors of granular soils under high stresses are described. The limit pressure of spherical cavity expansion is given by the law of conservation, in which the volume change of spherical cavity is balanced with the compression of granular soil and the energy given out from spherical cavity expansion is absorbed by the volume change and shear strain caused in granular soil. This method can be used to estimate the penetration resistance of static cone penetration test and pile driving below the critical depth. The process of analysis shows that the limit pressure is determined by the characteristics of stress-strain-volume change relationships and strength of granular soil,and has no concern with the pressure of superstratum. The result shows that the calculating value of limit pressure has a few decreases under the influence of curved envelope and agrees well with the experiential data of the penetration resistance for medium dense sand.