考虑相变过程岩体孔隙率对寒区隧道温度场时空规律影响研究

为研究寒区隧道围岩在持续低温作用或冻融循环作用过程中，考虑岩体相变过程中多相体各组分变化引起的岩石热学参数差异对围岩温度场时空变化规律的影响，利用已有岩体未冻水含量研究成果，进一步推导不同孔隙率下岩体的热学参数计算公式。基于多孔介质模型建立考虑相变过程的围岩温度场计算模型，分析考虑潜热时不同孔隙率下围岩冻结缘的空间形态变化规律，及相变过程对温度场的影响。研究结果表明： 1）饱和岩体孔隙率越高，对岩体整体热学参数影响越大； 2）低温持续作用围岩时，冻结缘向围岩深处移动并不断变宽，其宽度与其深度呈线性关系； 3）饱和围岩孔隙率对冻结缘移动速度影响较大，但对其宽度基本无影响； 4）由于相变潜热，岩体在冻融循环过程中围岩温度时程曲线出现不对称阶梯状形态，且其阶梯形状宽度与围岩孔隙率呈正相关； 5）冻融循环过程中，升温及降温过程中冻结缘临近岩体温度梯度存在差异引起的传热效率不同直接导致升温、降温时程曲线的不对称性特征出现； 6）沿硐室围岩径向向外，各处围岩体的温度时程函数与加载的温度函数存在着振幅衰减和相位滞后的现象，且岩体孔隙率越高该现象越明显。

Study on Influence of Rock Porosity on Time space Laws of Rock Mass Temperature Field of Tunnel in Cold Region Considering Phase Transition

In order to study the effects of rock thermal parameters difference caused by the change of multiphase components during rock mass phase transition on time space laws of the surrounding rock temperature field, the thermal parameters formula of rock mass under different porosity is calculated. Based on the porous medium model, a temperature field calculation model considering phase change and thermal parameters with temperature dynamics is established. Taking latent heat into account, the change laws of space form at surrounding rock frozen fringe under different porosity and the influence of phase transition on temperature field are analyzed. The research results show that： (1) The higher the porosity of the saturated rock mass, the greater the influence on the overall thermal parameters of the rock mass. (2)When the surrounding rock is affected by low temperature, the frozen fringe moves deeper into the surrounding rock and gets wider, and the width is linear with its depth. (3)The porosity of saturated surrounding rock has great influence on the moving speed of the frozen fringe but has no effect on its width. (4)Due to the latent heat of phase change, the time history curve of the surrounding rock temperature during the freezing thawing cycle shows an asymmetrical step like shape, and the step width is positively correlated with the porosity of the surrounding rock. (5)In the cycle of freezing and thawing, the difference existing in the frozen fringe adjacent to rock temperature gradient during heating and cooling can cause different thermal conductivity and directly leads to the asymmetry of the temperature history curve. (6) Along the radial direction of surrounding rock mass in chamber, amplitude attenuation and phase lag 〖HJ〗are existed in the temperature history function and the loaded temperature function in the surrounding rock mass, and the higher the porosity of the rock mass, the more obvious the phenomenon is.