岩溶地区高速公路路桥基下伏溶洞顶板力学简化计算模型研究

Mechanical Simplified Calculation Model of Karst Cave Roofs under Highway Roadbed and Bridge Foundation in Karst Area

溶洞顶板力学简化计算模型是溶洞顶板稳定性分析与评价的基础,对岩溶地区高速公路路桥基稳定性判断具有重要的工程实际意义。根据岩溶地区高速公路路桥基下伏溶洞顶板实际受力特点,视均布荷载及中部集中力为路基与桥基下伏溶洞顶板所受上部压力,将溶洞顶板简化为两种荷载作用下的3类简单梁结构模型,即简支梁模型、两端固定梁模型和悬臂梁模型,并基于材料力学理论引入奇异函数的初参数法,推导出6个溶洞顶板力学简化计算模型的挠曲线方程。以广东韶关丹霞高速公路互通区路桥基下伏溶洞为例,利用推导出的挠曲线方程计算出对应简化计算模型的挠度分布,并与有限元数值模拟结果进行对比分析,结果发现:两端固定梁模型的挠度分布曲线与有限元数值模拟的结果最为接近,实际工程中宜采用两端固定梁模型作为路桥基下伏溶洞顶板稳定性评价的基础。

The mechanical simplified model of karst cave is the basis for the analysis and evaluation of the stability of karst cave roof,which plays an important role in stability judgment of highway roadbed and bridge foundation in karst area. According to the real stress characteristics of karst cave roof under highway roadbed and bridge founda tion,the stress above the karst cave roof is replaced by uniform load and central concentrated load, and the karst ca ve roof is simplified into three common beam models （simply supported beam, the beam fixed at two ends, and can tilever beam） with two kinds of load. Based on the material mechanics theory, this paper adopts the initial parameter method of the singularity function to derive the deflection curve equation of the six mechanical simplified models. Taking the karst caves under highway roadbed and bridge foundation of Danxia grade separation area in Shaoguan city,Guangdong for example, the paper obtains the deflection of six mechanical simplified models of karst cave roof by the deflection curve equations,and compares with the results of finite element numerical simulation. The results show that the distribution of the deflection of the beam fixed at two ends is the closest to the numerical simulation results. Therefore,the beam fixed at two ends is more suitable as the foundation for evaluation of the stability of karst cave roof.