能量守恒原理在吁级围岩隧道衬砌设计中的应用研究

摘要

There exists energy delivery and transformation in the closed surrounding rock - tunnel lining system during the process of tunnel construction. When thermal energy transformation is left out of consideration and the surrounding rock is treated as an elastic body, the release of static energy of surrounding rock equals the increase in the elastic strain energy of tunnel lining. According to this energy conservative principle, Liu Hongyan and other researchers[1 2] calculated the thickness of lining of single track tunnel subject to Ⅲ-class surrounding rock. Based on these research findings, this paper further studies the application of energy conservative principle in V-class tunnel lining design. V-class surrounding rock of the three-dimensional FLAC3D model is established, dynamically simulating the process of tunnel excavation. With MATLAB language to the program of elastic strain energy density function, elastic strain energy of each unit of solid model is obtained, thus, static energy curves of surrounding rock associated with excavation depth within the specific scope of monitoring surrounding rock are finally obtained. According to the above curves, we are able to obtain the release value of static energy of surrounding rock. Additionally, toughness tests of steel fiber reinforced concrete ( SFRC) members are conducted, which leads to the finding of the relationship between energy expenditure of SFRC trisection beam under critical conditions and that of SFRC tunnel lining. Thus, theoretical tunnel lining thickness can be defined by solving the energy equation deduced from the energy expenditure relationship, and proved to satisfy the safety requirements. The research results show that, the tunnel lining design method with energy conservative principles is no longer limited by the conditions of II,Ⅲ-class surrounding rock in small section tunnels, and it is also applicable to the lining design of large section tunnels with Ⅴ-class surrounding rock.%在围岩-衬砌这个封闭系统中，隧道的开挖和支护过程伴随着能量的传递和转化，不考虑热能散失并将围岩视为弹性体，则围岩势能的释放即为衬砌结构弹性应变能的增加。刘红燕等[12]利用该能量守恒原理对Ⅲ级围岩单线铁路隧道进行了衬砌厚度的计算，在此研究成果的基础上进一步研究了能量守恒原理对于V级围岩衬砌设计的适用情况。针对V级围岩建立 FLAC3D模型动态模拟隧道的开挖过程，利用 matlab 语言编写弹性应变能密度函数从而得到实体模型各单元的弹性应变能，最后得到特定范围内围岩势能随掘进深度的变化曲线。由此围岩势能变化曲线可得出隧道开挖后围岩的势能释放值。此外，通过进行钢纤维混凝土(SFRC)构件的韧性试验，确定SFRC 三分梁破坏与 SFRC 衬砌破坏时的能量消耗关系。据此建立能量方程并可得出 SFRC 衬砌的理论厚度，经检算，设计厚度满足安全性要求。结果表明，能量守恒原理的隧道衬砌设计方法不再受Ⅱ、Ⅲ级围岩小断面情形的限制，它同样适用于 V 级围岩大断面隧道的衬砌设计。