寒区隧道冻胀效应测试与分析

为研究寒区隧道冻胀力随时间和空间的分布规律, 基于温度场变化定义了测试冻胀力, 通过衬砌压力和钢架应力间接反映真实冻胀力的变化规律; 提出了冻胀力简化测试方法, 研发了温度场-冻胀力同步测试系统; 以四川省省道215线鸡丑山隧道为例, 布置5个测试断面开展大规模现场测试, 并选取典型断面K117+700 (简称700断面) 和K117+600 (简称600断面) 分析了隧道环境温度、围岩温度、衬砌压力与钢架应力; 以围岩冻结(12~次年2月) 和未冻(7~9月) 时对应的衬砌压力和钢架应力差值为测试冻胀力, 结合温度场分析了隧道周边各测点测试冻胀力; 采用现有冻胀模型计算理论冻胀力, 并与测试冻胀力进行了对比, 研究了寒区隧道冻胀规律。分析结果表明: 隧道环境温度随时间呈季节性正弦函数变化, 受环境温度影响, 围岩温度呈季节性正负温变化, 并出现季节性冻融现象; 当围岩为负温时处于冻结状态, 支护系统受到围岩压力和冻胀力的共同作用, 且温度越低冻胀效应越明显, 各断面测点应力峰值均出现在1月, 700断面衬砌和钢架最大应力分别为149kPa、31MPa; 当围岩为正温时处于未冻结状态, 支护系统仅受到围岩压力作用; 同一断面不同测点的测试冻胀力差值可达5.23MPa, 说明冻胀力除与围岩温度有关外, 还与富水条件和围岩级别有关; 最大冻胀力实测值比理论计算值小1.25MPa, 因此, 寒区隧道支护设计时建议考虑89.17%的冻胀力折减系数。 

Test and analysis on frost heaven effects of cold region tunnel

To investigate the distribution law of frost heaven force with time and space, the test frost heaven force was defined based on the temperature field. The change law of the frost heaven force was described by the lining pressure and steel arch stress. A new test method of frost heaven force was presented based on the temperature field, and a temperature field-frost heaven force synchronization test system was developed. Took Jichoushan Tunnel of Sichuan Provincial Highway 215 as an example, 5 test sections were set to conduct large-scale field tests, and the typical sections of K117+700 (section 700 for short) and K117+600 (section 600 for short) were selected to investigate the tunnel environment temperature, surrounding rock temperature, secondary lining pressure and steel arch stress. The differences in the stresses of the secondary lining and steel arch between the conditions of freezing (from December to February of next year) and unfreezing (from July to September) were defined as the test frost heaven force, and the testfrost heaven force was analyzed through the temperature field. Subsequently, the theoretical frost heaven force was computed by the existing frost heaven model and compared with the field test result, and the frost heaven law of the tunnel in the cold region was studied. Analysis result shows that the tunnel environment temperature changes with time as a seasonal sine functional variation. The surrounding rock temperature affected by the environment temperature changes as a seasonal positive and negative temperature variation, and a seasonal freezing-thawing phenomenon appears. Under the negative temperature, the surrounding rock is frozen, and the supporting system is affected by the pressure of the surrounding rock and frost heaven force. The lower the temperature, the more obvious is the effect of the frost heaven. The peak value of stress of each section appears in January. The maximum stresses of lining and steel arch of section 700 are 149 kPa and 31 MPa, respectively. Under a positive temperature, the surrounding rock is unfrozen, and the supporting system is only affected by the pressure of the surrounding rock. The maximum difference of frost heaven forces among different test points on the same section can reach 5.23 MPa. It is illustrated that the frost heaven force is not only related to the temperature field, but also to the rich water condition and surrounding rock grade. The test frost heaven force is 1.25 MPa less than the calculated one. Therefore, a frost heaven force reduction coefficient of 89.17% should be considered when designing the supporting.12 figs, 36 refs.