基于莫尔破坏判据的溶洞顶板冲切破坏研究

Study on Punching Shear Failure of Cave Roof in Karst Area Based on Mohr Failure Criterion

在现有岩溶区嵌岩桩承载机理研究的基础上,参考较为成熟的混凝土板冲切破坏研究成果,针对岩溶区岩体特点引进莫尔二次抛物线型岩石破坏判据,通过变分原理求得冲切破坏体的曲线方程,并基于功能原理推导出了溶洞顶板抗冲切极限承载力,由此导得溶洞顶板最小安全厚度。参数分析表明:破坏体d1/d(下部直径与桩径比)随σc/σt(抗压与抗拉强度比)增大而呈非线性增大。最后用工程实例对溶洞顶板最小安全厚度计算公式进行了验证,充分证明了计算结果的正确性,对岩溶区嵌岩桩初步设计具有较好的实践意义。

Based on the existing research on the bearing mechanism of rock socked pile in karst area and more mature research result of punching shear failure on concrete slabs, the quadratic parabolic Mohr failure criterion of rocks have been introduced on the basis of the characteristics of rock mass in karst areas. The curve equation of the punching failure body is acquired through the variational principle, and the ultimate punching shear bearing capacity of cave roofs is derived based on the principle of work and power. Thus, the critical safe thickness of cave roofs is obtained. The parameter analysis shows that d1/d （the ratio of the broken body＇s lower diameter to pile diameter） increases nonlinearly with the increase of σc/σt（ the ratio of compressive strength to tensile strength）. One engineering example verified the formula of the critical safety thickness of cave roofs, which illustrates that this calculation approach is correct and of great significance for the preliminary design of rock -socked piles in karst areas.