滇藏铁路玉峰寺深埋隧道重大工程地质

本文结合中国地质调查局“滇藏铁路沿线地壳稳定性调查评价”项目,在收集、分析前人研究成果的基础上,采用多学科理论和方法,针对滇藏铁路滇西北段的控制性工程——玉峰寺深埋隧道建设中可能存在的重大工程地质问题进行深入研究,取得了以下进展和认识:1、在滇西北区域地质背景和地壳稳定性分析的基础上,重点阐述了新构造和活动断裂发育特征,将区域主要活动断裂大致划分为前第四纪断裂、早-中更新世活动断裂、晚更新世活动断裂和全新世活动断裂四类,初步提出了适合地壳运动活跃地区断裂活动性的评价标准:即以断裂活动速率及诱发地震震级作为指标,将断裂活动性划分为强、中强、中等和弱4个等级。2、区域现今应力场分析表明:滇西北地区区域应力场方向为NNW向(340°左右),与走向310°的玉峰寺隧道小角度相交,有利于隧道的稳定。玉峰寺隧道场区地应力水平高,主要受区域应力场和地形地貌的影响。根据三维数值模拟结果,隧道进出口段的最大、最小主应力变化速度快,差异应力较大;隧道中间段应力值较高且相对稳定,差异应力不大。3、在系统分析影响岩爆相关因素的基础上,应用岩爆倾向性判据、岩爆应力判据和刚度判据,采用岩石力学试验和应力场数值模拟等方法,分析计算了隧道围岩的弹性能量指标、冲击能量指标、巴顿应力指标、拉森斯指标等多种岩爆指标。结合玉峰寺隧道的地质构造和工程地质条件分析,对玉峰寺隧道岩爆危险性进行了多层次预测。结果表明,块状玄武岩地段可能发生中等-强烈岩爆,长约3500m,占隧道总长的32%,其中1000-1500m区段危险性最大(占隧道总长的4%),可能发生严重岩爆;隧道中部层状碎屑岩段,仅在局部厚层状砂岩发育部位可能发生岩爆,烈度为轻微-中等;隧道出口段发生岩爆的可能性小,局部有轻微岩爆。在隧道断面上,拱顶部位岩爆程度最高,其次为底板、边墙与仰拱交界部位,边墙岩爆程度最低。4、从最小势能原理观点出发,采用岩石力学全应力-应变试验和数值模拟方法,研究了隧道围岩力学系统的相互作用过程,采用岩爆的刚度判据得出玉峰寺隧道3种围岩塑性破坏后的刚度曲线和对应弹性围岩体的刚度曲线,结果表明,块状玄武岩体的岩爆危险性最高,其次是厚层状灰岩,层状碎屑岩的岩爆危险性最低。5、工程地质类比和综合分析表明,玉峰寺隧道可能发生涌突水的地段主要集中在文海断层段和隧道出口附近灰岩向斜储水构造区段。其中,前者为岩溶、岩性接触面与断层复合机制涌突水,涌突规模中等-大;后者可能发生中等规模以下的涌突水。
活动房
On the basis of collecting and analyzing predecessor’s information, filed geological work,remote sensing, indoor examination analysis and simulative calculation, using multidisciplinary theory like engineering geology, rock body mechanics and so on, this dissertation, combining with practical project, studies the important engineering geological problems of the Yufengsi tunnel of Yunnan-Tibet railway. In the light of general analysis in many aspect such as region geology, crust stability, activity fault, seismic hazard and engineering geology conditions of tunnel site, combining with the analyzing region stress field and 3-D FEM simulation of tunnel site, the dissertation gives general studies and prediction about rock burst and water bursting of Yufengsi tunnel , and besides , it studies the rigidity criterion for rock burst of tunne wall. By more than three years’study, we have obtain some progress and conclusion as follows: 1.Based on analyzing the region geology condition and crust stability in the NW of Yunnan, the dissertation studies the features of arel neotectonic and activity faults, and then classified activity faults to four kinds as pre quaternary faults, early-mid pleistoncene activity faults, late pleistoncene activity and Holocene faults. A preliminary evaluate criterion for instability crust region is put forward, in which the velocity of fault movement and the seismic magnitude are parameters by which the activity of faults can be divided into four degree.2.Region present stress field analysis shows:1 the present region stress field in the NW of Yunnan is mainly in the NNW direction extrusion(about 340°),and intersects at small angle with Yufengsi tunnel of N310°W direction, which is propitious to the tunnel’s stability. 2,in the tunnel site ,the stress value is high and is influenced by region stress field and landform. In the light of 3-D simulation for tunnel site, two stress type can be partitioned off. On the two end of the tunnel, stress field featured that the principle stress alters quickly and the discrepancy between maximum principle stress and minimum principle stress is large. In the mid tunnel, stress field featured that main stress alters slowly and the discrepancy between maximum main stress and minimum main stress is small .3.On the basis of systemically analyzing eight influencing factors of rock burst occurrence, using multi-criterions for rock burst occurrence such as stress criterion, burst potential and rigidity criterion, coupling with rock mechanical property test and stress field simulation, many parameters of rock burst have been worked out suck as Wet index, Wcf index, Barton index and Russenes index. Considering these parameters and engineer geology conditions of tunnel site, the plat of rock burst occurrence and intensity class at Yufengsi tunnel in three levels as follows: lithology, tunnel segment and section of tunnel, are predicted emphatically. The prediction results shows: middle-strong rock burst occurs at basalt tunnel segment which is 3500m length, about 32% of the total tunnel length. Among the basalt tunnel segment, strong rock burst may concentrates on the segment from 1000m to 1500m which is about 4% of the total tunnel. None but light or middle rock burst is likely to occurs at thick bedded sandstone in the middle of tunnel with layered clastic rock. Among the rest ,it need attention to the exit end of the tunnel with thick bedded limestone without karst water in which the light or middle rock may occur. In tunnel section, the intensity of rock burst is high at arch top. The bottom and arch springing is light. the side wall has no rock burst.4.The rigidity criterion for rock burst is studied and applied in Yufengsi tunnel of Yunnan-Tibiet railway based on the minimum energy theory. Firstly, the three kinds rock failure process in different confining pressure is analyzed according to the complete stress-strain curves experiment of rock specimens, in-situ stress data and digital simulation results. Secondly, the rigidity curves of either tunnel plastic rockmass or elastic rockmass is obtained by the analysis and simulation results. Finally, the tunnel rockburst hazard of three kinds rockmass are estimated by rigidity criterion. The basalt rockburst hazard is the most heavily, and the layered sandstone rock burst hazard is the most light.5.The plats where water gushing occurs in Yufengsi tunnel are predicted and evaluated. The result shows: the segment where industrial scale water gushing occurs mostly concentrates on the Wenhai fault zone and scyncline structure segment on the exit end of the tunnel. Wenhai fault zone, which is fault and karst and rock boundary multiple-unit control plats, may occurs middle-large scale gushing water and results in a set of environment problems. Moderate or below scale water gushing is occurs in the scyncline structure on the tunnel exit segment