高地温环境下隧道初期支护力学性能研究

Mechanical Characteristics Analysis of Initial Support of High Geothermal Tunnel

以川藏铁路桑珠岭超高地温隧道为研究对象,采用现场实测和热-力耦合数值模拟手段,对超高地温环境下初期支护的力学特性展开研究。结果表明:隧道开挖后,初期支护混凝土应力在10 d内变化较快,18 d后基本稳定;初期支护轴力和弯矩随温度的升高而成增大趋势;随着围岩初始温度的升高,初期支护最大压应力、拉应力与无温度场时的比值逐渐增大,扩大倍数可表示为围岩初始温度的二次函数;当围岩初始温度大于50℃时,初期支护存在破坏趋势;随着围岩温度的升高,初期支护最大压应力的分布范围由边墙扩大到边墙和拱腰,最大拉应力由墙脚扩大到墙脚、拱肩和仰拱。研究结论对高地温隧道初期支护的施工有一定的指导价值。

Based on the study of the high geothermal Sangzhuling tunnel of Sichuan-Tibet railway,a field test and thermal-force coupling numerical simulation were carried out to study the change law of mechanical characteristics of initial support influenced by temperature in high geothermal tunnel.The results show that the initial support concrete stress changes rapidly within 10 days and is almost stable in the following 18 days after the completion of the tunnel excavation.The initial support axial force and bending moment show an increase trend with the increase of temperature.With the increase of the initial temperature of the surrounding rock,the ratio of maximum compressive stress,tensile stress and the stress of temperature-free field in the initial support gradually increases,and the expansion factor can be as expressed as a quadratic function of the initial temperature of the surrounding rock.A destructive trend exists in the initial support when the initial temperature of surrounding rock is above 50℃.With the increase of surrounding rock temperature,the distribution of the maximum compressive stress of the initial support is extended from the sidewall to the side wall and the arch waist,and the maximum tensile stress is extended from the wall foot to the wall foot,the spandrel and the invert arch.The conclusion has certain guiding value for the construction of the initial support of the high geothermal tunnel.