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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 research on the bearing mechanism of rock-socketed pile in karst area, referring to the research results of punching failure of concrete slab, the criterion of failure of mooring parabolic rock is introduced according to the characteristics of rock mass in karst area. By variational principle The curve equation of the failure body was punched out and the ultimate bearing capacity of the top of the karst cave was deduced based on the functional principle. The minimum safe thickness of the karst roof was obtained. The parameter analysis shows that the failure body d1 / d (lower diameter and pile diameter ratio) increases nonlinearly with the increase of σc / σt (compressive strength and tensile strength ratio). Finally, the engineering example is used to verify the calculation formula of the minimum safety thickness of karst roof, which proves the correctness of the calculation results. It is of practical significance for the preliminary design of rock-socketed piles in karst area.