基于Hoek-Brown的双向不等压隧道支护估算及工程应用

现行隧道塑性区分析中常基于轴对称荷载建立分析模型,忽略侧压力带来的影响。增加了对围岩侧压力的考虑,基于Hoek-Brown准则推导了双向不等压圆形隧道的塑性半径及应力计算式。依托滇中引水工程板凳山隧洞的监测数据,结合滑移剪切模型对隧道的极限位移和极限支护应力进行计算。结果表明:在确定围岩材料参数的条件下,塑性边界上的径向应力为恒值;环向应力在θ为0～30°范围内与侧压力成正比,在θ为30°～90°范围内与侧压力成反比,当θ取30°时环向应力为最大值,最终形成蝴蝶状的曲线。隧洞塑性区范围随着侧压力系数的降低呈现出上下端部小,中间部分大的椭圆形,在λ<0.38后,塑性区不再是可完整包裹开挖截面的椭圆形。基于滑移剪切模型对隧洞极限位移和极限支护应力进行计算,完善具有滇中红层特性的隧洞支护特征曲线。根据以上的计算结果对支护方案进行修正,并通过监测结果验证了方案的合理性。

Estimation and engineering application of bidirectional unequal pressure tunnel support based on Hoek-Brown

Abstract] In the current analysis of tunnel plastic zone, axisymmetric load is often used to establish the analysis model, ignoring the influence of lateral pressure. The paper added the consideration of the side pressure of surrounding rock, based on Hoek-Brown criterion, the formulas for calculating the plastic radius and stress of circular tunnel with bidirectional unequal pressure are derived. Based on the monitoring data of Bandun Mountain tunnel of the Central Yunnan diversion Project, the ultimate displacement and ultimate support stress of the tunnel are calculated with the slip-shear model. The results show that: (1) Conditions in determining the material parameters of surrounding rock, the plastic on the border of the radial stress is constant value. Tangential stress is proportional to lateral pressure in = 0~30°, and inversely proportional to lateral pressure in = 30~90°. When is 30°, tangential stress is the maximum value,and a butterfly curve is formed. (2) With the decrease of the lateral pressure coefficient, the plastic zone of the tunnel presents an oval shape with smaller upper and lower ends and larger middle parts, in the middle of the plastic zone after <0.38 excavation section of the oval is no longer a full package. (3) The ultimate displacement and ultimate support stress of the tunnel are calculated based on the slip shear model, and the characteristic curve of the tunnel support with the characteristics of the middle Yunnan red bed is perfected. (4) The support scheme is modified according to the above calculation results, and the rationality of the scheme is verified by the monitoring results.