基于板壳理论的防突岩体稳定性研究

Study on the Stability of Water Burst Prevention Rock Mass Based on Plate and Shell Theory

隧道在穿越岩溶区时掌子面前方不可避免存在富水溶腔,在隧道掘进过程中掌子面与溶腔之间的防突岩体厚度逐渐变薄,达到极限厚度将无法承受岩溶水压而发生突水突泥灾害。针对掌子面前方含充水溶洞建立概化模型和相对应的力学模型,基于板壳理论,推导矩形断面隧道防突岩体内力及最小安全厚度的解析解,并与国内外文献研究成果进行对比分析,证明了理论公式的可靠性。最后,基于设置的参数值和理论公式进行参数敏感性分析。结果表明:(1)矩形防突岩体的最大弯矩发生在板的中心,且板的短边方向弯矩大于长边方向弯矩;(2)岩溶水压、隧道断面尺寸、隧道埋深增大均会导致防突岩体的安全厚度增加,对工程安全不利,岩石抗拉强度的增大对岩体防突是有利的。研究成果结合工程中超前预报可有效防治岩溶隧道突水突泥灾害。

Water-rich cavity is inevitable in front of tunnel face crossing karst area.In the process of tunnel excavation,the thickness of water burst prevention rock mass between tunnel face and cavity gradually becomes thinner,reaching the limit thickness will be unable to withstand karst water pressure and cause water inrush disaster.The generalized model and the corresponding mechanical model are established for the water-filled karst cave in front of the tunnel face.Based on the plate and shell theory,the analytical solution of the minimum safe thickness of the water burst prevention rock mass in the rectangular section tunnel is derived.Compared with the existing literature research results,the reliability and feasibility of the theoretical solution are proved.Finally,parameter analysis is carried out based on the set parameter values and theoretical formulas.The results show that:(1)The maximum bending moment of rectangular outburst prevention rock occurs at the center of the plate,and the bending moment in the short side direction of the plate is greater than that in the long side direction of the plate;(2)The increase of karst water pressure,tunnel section size and tunnel buried depth will lead to the increase of safety thickness of outburst prevention structure,which is unfavorable to engineering safety;the increase of rock tensile strength is beneficial to rock outburst prevention.The research results combined with the advanced prediction in the project can effectively prevent and control the water and mud inrush disasters of karst tunnels,so as to provide a basis for engineering construction.