深埋复合式衬砌隧道二衬分担比研究

Study on Secondary Lining Sharing Ratio for Deep-buried Composite Lining Tunnel

为研究深埋复合式衬砌隧道二衬分担比,首先,介绍了基于"叠合梁"理论的初支与二衬荷载传递机理;然后,统计了31座隧道120个断面围岩与初支及初支与二衬间接触压力的监测数据,研究了围岩压力与围岩级别、埋深等参数的相关性,系统分析了经验公式计算的深埋隧道围岩压力与实测值的差异性;最后,将运用修正的"叠合梁"理论计算出的不同围岩级别二衬分担比与实测值对比分析,并讨论了"叠合梁"理论计算二衬分担比的适用性。结果表明:深埋复合式衬砌隧道围岩压力总体随着围岩级别或隧道埋深的增加而增加,而与隧道跨度﹑高度无明显联系;经验公式计算值与实测值接近程度从优到劣依次为:普氏理论、《公路隧道设计细则》(2010)、太沙基公式;《公路隧道设计细则》(2010)适用于埋深小于800 m的围岩压力预测;Ⅲ,IV,V和Ⅵ级围岩的二衬分担比多集中于20%~30%,30%~45%,40%~70%,隧道地应力高、围岩条件差以及初支未及时施作等因素可能是少数断面二衬分担比过高的原因;"叠合梁"理论计算的二衬分担比值受支护材料物理力学参数的影响甚微,而受初支厚度与二衬厚度的影响颇大,"叠合梁"理论不适用于IV级及以下围岩二衬分担比的计算,V和Ⅵ级围岩二衬分担比可按"叠合梁"理论计算值的70%预测。

In order to study the secondary lining sharing ratio of deep-buried composite lining tunnel,first,the load transfer mechanism of primary support and secondary lining based on "composite beam" theory is introduced. Then,the monitoring data of contacting pressure between the surrounding rock and the initial support,the initial support and the secondary lining of 120 sections of 31 tunnels about the are collected,the correlations between surrounding rock pressure and surrounding rock grade,buried depth and other parameters are studied,and the difference between the pressure of surrounding rock of deep-buried tunnel calculated by empirical formula and the measured value is analyzed systematically. Finally,the secondary lining sharing ratio of each surrounding rock grade calculated by the modified "composite beam" theory is compared with the measured value,and the applicability of the "composite beam" theory in calculating the secondary lining ratio is discussed. The result shows that(1) The surrounding rock pressure of deep-buried composite lining tunnel increases with the increase of surrounding rock grade or tunnel depth as a whole,but it has no obvious relationship with tunnel span and height.(2) The approximate degrees between the calculated value by the empirical formula and the measured value from the superior to the inferior are: the Przewalski’s theory,Guidelines for Design of Highway Tunnel(2010),and the Terzaghi formula.(3) Guidelines for Design of Highway Tunnel(2010)is suitable for the prediction of pressure of surrounding rock with buried depth less than 800 m.(4) The secondary lining sharing ratios of surrounding rock Grades Ⅲ,IV,V and Ⅵ are mostly concentrated on 20% to 30%,30% to 45% and 40% to 70%.The factors such as high in-situ stress,poor surrounding rock conditions and the failure of timely construction of the primary support may be the reasons for the high sharing ratio of secondary lining in a few sections.(5) The secondary lining sharing ratio calculated by "composite beam" theory is little influenced by the physical and mechanical parameters of support materials,but it greatly influenced by the thicknesses of primary support and secondary lining. The "composite beam" theory is not applicable to the calculation of the secondary lining sharing ratios of the surrounding rock Grade IV and below,and the secondary lining sharing ratios of the surrounding rock Grades V and Ⅵ can be predicted by 70% of the theoretical value calculated by "composite beam" theory.