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以空间准滑动面(SMP)准则为基础,推导了扩底桩扩孔压力的理论解。从能量耗散的角度分析球孔扩张的全过程,利用应力不变量推导了符合球孔扩张的屈服准则;化简微分方程得到了弹塑性区应力表达式,进而求出位移、应变表达式;分别利用体积守恒和能量守恒性推导出扩孔压力的表达式。该法考虑了塑性区弹性变形,并得到了扩孔压力p、塑性区半径R与扩孔半径a的关系。算例分析表明,该方法计算的扩孔压力与现场试验得出的结果较好地吻合,塑性区半径和扩孔压力均随扩孔半径的增加而增大,但增幅逐渐减小而趋于稳定值,剪胀角对塑性区半径和扩孔压力影响显著,随着剪胀角的增加,塑性区半径和扩孔压力明显增加。
Based on the SMP criterion, the theoretical solution of the reaming pressure of the enlarged bottom piles is deduced. From the perspective of energy dissipation, the whole process of ball expansion is analyzed, and the yield criterion that accords with the expansion of the ball hole is deduced from the stress invariant. The stress and strain expressions of the elastic-plastic zone are deduced by simplifying the differential equations, and the displacement and strain expressions are obtained. The expressions of reaming pressure are deduced by volume conservation and energy conservation respectively. The method takes into account the elastic deformation of the plastic zone and obtains the relationship between the expansion pressure p, the radius R of the plastic zone and the radius a of the expansion hole. The results of numerical examples show that the calculated hole expansion pressure agrees well with the field test results. The plastic zone radius and expansion pressure increase with the increase of reaming radius, but decrease with increasing The stability and dilatancy angle have a significant influence on the radius of plastic zone and the pressure of expanding hole. With the increase of dilatancy angle, the radius of plastic zone and the pressure of expanding hole increase obviously.