Study of Large Deformation Classification Criterion for Layered Soft Rock Tunnels under High Geostress
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摘要: 为探明高地应力层状软岩隧道的非对称变形破坏规律及其支护结构的非对称受力特性，结合碳质千枚岩力学特性与变形破坏机制的各向异性特性，对层状软岩隧道围岩的非对称变形破坏特征进行了分析. 在93座典型高地应力层状软岩隧道变形数据的基础上，系统性地分析了隧道拱顶沉降、水平收敛、最大变形量与地应力、岩体抗压强度、隧道埋深之间的关系. 研究结果表明：高地应力层状软岩隧道的变形量与最大地应力、岩体抗压强度、埋深的分布较为离散，在一定地应力、岩体强度或埋深条件下，隧道变形量既存在于高值区间，也存在于低值区间；隧道变形量随地应力的增大、岩体强度的降低、埋深的升高逐渐向高值区间靠拢，高地应力层状软岩隧道大变形是高地应力、软弱围岩、层理弱面耦合作用的结果；基于隧道最大变形量与隧道强度应力比的幂指数变化规律，提出了高地应力层状软岩隧道的大变形预测分级指标.Abstract: The asymmetric deformation failure characteristics and asymmetric mechanical behaviour of supporting structures in layered soft rock tunnels under high geostress, combined with the anisotropic mechanical properties of carbonaceous phyllite, were investigated. Based on the deformation data of 93 layered soft rock tunnels under high geostress, the relationships between roof settlement, horizontal convergence, largest deformation and geostress, rock compressive strength, and overburden depth were systemically analysed. The results show that the deformations are discretely distributed according to the variations in geostress, rock compressive strength, and overburden depth. Under certain parameters of geostress, rock compressive strength, or overburden depth, the deformations are distributed in both the high- and low-value zones. With increasing geostress and overburden depth, and with decreasing rock compressive strength, the deformations gradually approach the high-value zone. This means that the large deformations of layered soft rock tunnels under high geostress are determined by the combined action of high geostress, weak surrounding rock, and a weak bedding plane. Based on the power exponent variation law between the largest deformation and the strength-stress ratio, a new classification criterion for large deformations is proposed for layered soft rock tunnels under high geostress.
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图 1 碳质千枚岩抗拉强度随层理角度变化的关系曲线
Figure 1. Relationship curve of carbonaceous phyllite’s tensile strength changing with bedding angle
图 2 碳质千枚岩在不同层理角度下的破坏特征
Figure 2. Failure characteristics of carbonaceous phyllite under different bedding angles
图 3 碳质千枚岩在不同加载条件下的峰值强度变化
Figure 3. Changing curves of carbonaceous phyllite’s compressive strength under different bedding angles
图 4 碳质千枚岩在单轴与高围压条件下的破裂形态
Figure 4. Failure modes of carbonaceous phyllite under uniaxial compression and 30 MPa confining pressure
图 5 不同层理角度条件下层状软岩隧道的围岩变形规律
Figure 5. Simulated deformation behavior of the surrounding rock under different inclination angle β
图 6 隧道变形量与地应力的关系
Figure 6. Relationships between deformation and geo-stress of tunnels
图 7 隧道变形量与岩体抗压强度的关系
Figure 7. Relationships between deformation and rockmass compressive strength of tunnels
图 8 隧道变形量与埋深的关系
Figure 8. Relationships between deformation and overburden depth of tunnels
图 9 隧道的最大变形量与强度应力比的关系
Figure 9. Relationship between the largest deformation and strength-stress ratio of tunnel
表 1 典型高地应力条件下深埋长大层状软岩隧道统计结果
Table 1. Statistical results of typical high geostress and layered soft rock tunnels
隧道名称 隧道
长度/m最大
埋深/m穿越地层
岩性最大主应力/MPa 围岩抗压强度/MPa 最大拱顶沉降/mm 最大水平收敛/mm 围岩与支护结构变形破坏特征 奥地利
陶恩6 400 1 000 绿泥石，
千枚岩27.00 1.70 1 200 500 世界上第1座知名的大变形隧道，施工中在层状软岩地层发生了大变形，最大位移速度达20 cm/d. 兰渝铁路木寨岭 19 068 715 薄层状炭质
板岩27.16 5.92 1 712 1 081 极高地应力软岩大变形隧道，开创小导洞应力释放+三层支护+长锚索+单层衬砌的“木寨岭模式”. 南昆铁路家竹菁 4 990 404 页岩，层状
煤层16.09 1.70 1 000 1 600 集高地应力、高瓦斯突出、高涌突水的铁路隧道，在高地应力条件下的层状软岩煤层中发生大变形. 成兰铁路茂县 25 000 675 绢云母千枚岩夹炭质千枚岩，陡倾 27.52 1.95 510 810 发生挤压性大变形，变形增长持续时间长，时间效应显著，岩层陡倾导致隧道水平收敛大于拱顶沉降. 兰新线乌鞘岭 20 050 1 100 千枚岩夹板岩 32.80 0.70~2.50 1 209 1 053 穿越挤压性断层，围岩整体稳定性较差，受强烈挤压变形，变形量大，初期变形速率快，变形时间长. 兰渝铁路两水 4 922 346 千枚岩与碳质板岩 10.50 2.90 750 543 变形迅速而强烈，且持续时间较长，混凝土大量开裂、掉块，部分钢拱架扭曲、断裂，支护结构失稳. 宜万铁路堡镇 11 600 630 炭质页岩 16.00 2.90 640 1 250 变形量大、变形发展快、持续时间长，且时空效应上具有明显的不对称性和不均匀性，顺层偏压严重. 西格二线关角 22 040 500 泥质片岩 22.04 5.00 505 460 隧道底部隆起和两侧边墙挤出，且变形持续时间长，通车不久后再次发生底部隆起，导致行车中断. 兰渝铁路新城子 9 164 749 薄层状碳质
板岩33.82 15.00 356 443 二衬受到强烈挤压产生不同程度的开裂、剥落、掉块现象，部分区段衬砌严重裂损，钢筋完全扭曲. 国道317
鹧鸪山4 423 1 000 薄层状碳质千枚岩，倾角40°～60° 20.00 12.00 300 300 围岩变形量较大，持续的时间长，表现为初期支护破裂、钢拱架扭曲，侵入隧道限界，易产生塌方. 兰渝铁路毛羽山 8 503 700 薄层状板岩，倾角70°～90° 21.28 5.63 540 1 200 围岩变形量大，变形速率快，具有显著的流变效应. 钢拱架严重扭曲、断裂，水平收敛远大于拱顶沉降. 渝沙高速共和 4 779 1 000 薄层状砂质页岩，倾角30°～40° 29.86 11.40 200 300 沿岩层法线方向的右拱肩和左拱脚部位的初期支护出现混泥土纵向开裂与钢架弯曲，围岩偏压严重. 
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表 2 高地应力层状软岩隧道的大变形分级指标
Table 2. Large deformatin classfication criterion for high geostress and layered soft rock tunnel
大变形等级 强度应力比 最大变形量/mm 无 > 0.80 < 100 轻微 （0.60，0.80] （300，100] 中等 （0.32，0.60] （500，300] 严重 （0.18，0.32] （800，500] 极严重 ≤ 0.18 ≥ 800
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