TBM隧道围岩损伤区范围及渗透特性研究

Study of the Range and Permeability Characteristics of Excavation-damaged Zone of TBM Tunnel

开挖损伤区不仅对一般工程的稳定性具有重要影响,同时其渗透特性变化也是一些特殊工程(如高放废物地质处置工程)关心的重点。该文结合桓集隧道四标段工程,通过在隧道洞壁取样而后进行室内超声波波速和渗透试验测试的方法,研究了TBM开挖隧道围岩的损伤区范围和渗透特性变化,同时也对样品洞壁端面的粗糙程度进行了量测,结果表明:(1)该隧道围岩强度较高,且工程区地应力属于低—中等水平,围岩损伤主要由TBM开挖造成。(2)隧道围岩的原岩波速在4713~5376 m/s之间,损伤区波速在2943~4856 m/s之间,围岩质量较好处的原岩波速和损伤区波速均大于围岩质量较差处的对应值,而围岩质量较差处的最大波速降比比围岩质量较好处的数值略大;各样品的损伤区范围在11.0~52.0 mm之间,一般围岩质量越好,损伤范围越小。(3)围岩质量较好处的原岩和损伤样品渗透率均小于围岩质量较差处的对应样品值;同一岩芯的损伤样品渗透率大于原岩样品,本次研究的机械开挖损伤使围岩的渗透率提高1.94~3.75倍。(4)研究的隧道表面波谷和峰高范围在-5~4 mm之间,满足SKB对处置孔壁粗糙程度的要求。

The excavation-damaged zone（ EDZ） has significant influence on not only the stability of rock underground engineering,but also the change of its permeability,which is the focus of some special projects such as nuclear waste disposal project. In order to study the range and permeability characteristics of EDZ,a series of ultrasonic velocity,permeability,and surface roughness tests were conducted on rock samples obtained from the Huanji Tunnel. It was found that（1） Due to the high rock strength and low to medium in-situ stress,the EDZ of the tunnel is mainly caused by the excavation of TBM;（2） The P-wave velocity of intact rock is between 4713 and 5376 m/s and the velocity of the damaged zone varies from 2943 to 4856 m/s. The P-wave velocities of intact rock and damaged zone of high-quality rock masses are larger than those of poor-quality rock masses. At the same time,the maximum decreasing ratio of P-wave velocity of poor-quality rock masses is slighthy larger than that of high-quality rock masses. In addition,the range of the EDZ is between 11. 0 and 52. 0 mm,and usually the surrounding rock with better quality shows a smaller rang of EDZ;（3） The permeability of intact rock and damaged zone of high-quality rock masses is smaller than that of poor-quality rock masses. In this study,the permeability of damaged zone,which was caused by TBM excavation,is 1. 94 ～ 3. 75 times larger than that of intact rocks;（4） The surface roughness of tunnel wall is between-5 and 4 mm,which satisfies the roughness requirement of SKB for disposal holes.