变坡面浅埋偏压隧道松动围岩压力计算方法

Calculation Method for Loose Surrounding Rock Pressure of Shallow Tunnel under Asymmetrical Pressure on Variable Slope

根据变坡面浅埋偏压隧道的结构和受力建立计算模型,由计算模型推导隧道深、浅埋侧棱体横截面面积的计算公式;再根据极限平衡法求解变坡面浅埋偏压隧道深、浅埋侧的推力,进而推导出变坡面条件下浅埋偏压隧道松动围岩压力的计算公式。由计算公式可知:当地面坡度增大时,水平侧压力系数也随之增大;随着两侧土体对拱顶上覆土层推力的增大,拱顶的垂直土压力减小而隧道的水平侧压力增大。以贵广高速铁路贺街隧道洞口的变坡面浅埋偏压段为例,运用给出的变坡面浅埋偏压隧道松动围岩压力计算公式进行计算,并将计算结果与规范法的计算结果和实测值进行对比。结果表明:在实际工程中,当隧道两侧土体表面坡度变化较大时,给出的变坡面浅埋偏压隧道松动围岩压力计算公式的计算结果更加切合实际。

According to the structure and force of shallow tunnel under asymmetrical pressure on variable slope, a calculation model was proposed to derive the formula for the cross section areas of the prism on deeply and shallowly buried sides of tunnel. Then the thrusts on both sides were obtained by limit equilibrium theory and the calculation formula was derived for the loose surrounding rock pressure of shallow tunnel under asymmetrical pressure on variable slope. It could be seen from the calculation formula that the lateral pressure coefficient increased with the increase of surface slope. Along with the increase in the thrusts of the overlaying soil on tunnel crown induced by the soil body from both sides, the vertical earth pressure on tunnel crown decreased while the lateral pressure of tunnel increased. With a section at the portal of Hejie Tunnel on Gui-Guang high speed railway as an example, the proposed model was used to calculate the loose surrounding rock pressure of shallow tunnel under asymmetrical pressure on variable slope. The obtained results were compared with measured values and those calculated by the code for de- sign on tunnel of railway. Results show that, in practical engineering, when the slope of the soil surface on both sides of tunnel varies greatly, calculation results obtained from the proposed model are more realistic.