基于砂岩长期蠕变的隧道施工全过程动态模拟

Dynamic simulation study of construction process of Simian mountain tunnel based on creep characteristics of sandstone

以四面山隧道砂岩段为依托工程,对砂岩试样进行单轴不等距分级加载蠕变试验,研究砂岩长期蠕变特性.根据试验数据,选择ANSYS隐式蠕变11号方程,将其作为砂岩持续变形的本构方程,继而对四面山隧道施工全过程进行动态模拟分析.结果表明:应力加载第一阶段出现典型的减速蠕变阶段和等速蠕变阶段,减速蠕变阶段持续时间较长,应变率随时间增加而变小并逐渐趋于定值,等速蠕变阶段蠕变率保持不变;通过动态模拟获得隧道施工过程水平收敛、拱顶沉降及应力变化曲线,水平收敛和拱顶沉降分别于26和24 d左右变形趋于稳定,其对应值为11.2和11.5 mm,拱腰及拱脚处应力分别稳定于2.26和4.44 MPa;锚杆受最大拉应力为229.97 MPa,衬砌受最大压应力为3.41 MPa,均小于最大允许值,处于安全范围;经验证,模拟结果与现场实测数据基本吻合.

To investigate the long-term creep characteristics of sandstones from Simian mountain tunnel,a multi-stage creep test on sandstones with different creep times was carried out.According to the test results,the No.11 Creep Equation in ANSYS,as a constitutive model capable of describing the continuously deformation process of sandstone,was selected to simulate the construction process of the Simian mountain tunnel.The results show that the typical deceleration creep stage and stable creep stage occur in the first stage of creep.The deceleration creep lasts for a long time,and its strain rate decreases over time and gradually tends to be constant.However,the strain rate at stable creep stage remains unchanged.On the other hand,the curves of horizontal convergence,crown settlement and stress versus time of tunnel model are analyzed concretely.It taks 26 days and 24 days respectively for horizontal convergence and crown settlement to reach the stable state.At the final stable state,the displacements of horizontal convergence and crown settlement are 11.2 and 11.5 mm respectively.The stresses at arch foot and lumbar of tunnel are 2.26 and 4.44 MPa respectively.The maximum tensile stress of anchor bolt during the construction process is 229.97 MPa and maximum compressive stress of lining is 3.41 MPa.Both of them are less than the maximum allowable stress.In addition,the simulation results are agreed with the field investigation data well.