他白依隧道软岩大变形控制数值模拟优化分析及现场试验

Numerical simulation optimization analysis and field test for large deformation control of soft rock in Tabaiyi Tunnel

  • 摘要: 以云南他白依隧道为研究工程背景,作为全线地质情况最复杂的隧道,其复杂性表现为:隧址区属构造溶蚀侵蚀区、地质状况多变、穿越多个断层破碎带、局部段落富水、岩石风化严重、构造应力影响剧烈等。在原支护作用下,出现了初支大变形、钢拱架变形、突泥涌水等状况。采用现场调查、岩石结构分析和数值模拟等方法对围岩的变形和破坏机理进行了研究。围岩以强~全、中风化变质砂岩夹片岩和板岩为主。对岩体进行扫描电镜观察发现,片理结构明显、岩体结构相对松散、孔隙较发育。岩石中黏土矿物含量较高,主要成分为伊利石和绿泥石。区域地应力主要以构造应力为主,隧址区地下水受岩性、构造和地形地貌等因素控制,地下水的补给与降雨等密切相关,地下水主要以松散堆积层孔隙水、岩裂隙水和岩溶水形式赋存。在NPR锚索控制体系实施下,大变形治理效果显著,围岩大变形被有效控制在300 mm内。为保证工程安全,提高施工效率,对NPR锚网和立体钢拱架耦合支护进行优化设计,利用FLAC3D与PFC3D软件对多个NPR锚索控制体系进行数值模拟,建立恒阻大变形效果的NPR锚网单元和双层立体钢拱架,对比分析各种方案下模拟得出的围岩变形图和支护结构位移图,再进行现场试验,将米级非对称变形控制结果与数值解进行分析对比,认为NPR锚网和立体钢拱架支护体系能够解决因围岩富水、突泥、破碎和局部高压涌水的工程技术难题,得到以NPR锚索为核心的不同支护工艺的耦合支护参数下隧道围岩的收敛变形演化规律。

     

    Abstract: Taking Yunnan Tabaiyi Tunnel as the background of the research project, as the most complex tunnel in the whole line, its complexity is manifested as follows: the tunnel site area is a tectonic dissolution and erosion area, the geological condition is variable, crossing a number of faults and fracture zones, the local passage is water-rich, the rock weathering is serious, and the influence of tectonic stress is intense, etc. The original supporting action has resulted in large deformation of the initial support, deformation of the steel arch, and sudden mud and water surge. Under the original support, there were large deformation of the initial support, deformation of the steel arch frame, and sudden mud and water influx. The deformation and damage mechanism of the surrounding rock was studied by field investigation, rock structure analysis and numerical simulation. The surrounding rock is strongly—fully and moderately weathered metamorphic sandstone sandwiched with schist and slate mainly. Scanning electron microscopy observation of the rock body shows that the schist structure is obvious, the rock body structure is relatively loose, and the pores are more developed. The clay mineral content in the rocks is high, and the main components are illite and chlorite. The regional ground stress is mainly dominated by tectonic stress, and the groundwater in the tunnel site area is controlled by lithology, tectonics, topography and geomorphology, etc. The recharge of groundwater is closely related to rainfall, etc. The groundwater is mainly stored in the form of pore water of the loose accumulation layer, rock fissure water and karst water. Under the implementation of NPR anchor cable control system, the effect of large deformation management is remarkable, and the large deformation of surrounding rock is effectively controlled within 300 mm. In order to ensure the safety of the project and improve the construction efficiency, the optimization design of NPR anchor network and three-dimensional steel arch coupling support is carried out, and numerical simulation of several NPR anchor cable control systems is carried out using FLAC3D and PFC3D software to establish the NPR anchor network unit and double-layer three-dimensional steel arch with constant resistance to large deformation effect, and the deformation diagrams of the surrounding rock and the displacement diagrams of the support structure obtained from the simulation under the comparison and analysis of the various schemes are then carried out. Field test, the meter-level asymmetric deformation control results and numerical solutions for analysis and comparison, that the NPR anchor network and three-dimensional steel arch support system can solve the water-rich peripheral rock, mud, broken and local high-pressure water influx of engineering and technical problems, to get the NPR anchor cable as the core of the different support process of the coupled support parameters of the tunnel peripheral convergence under the deformation of the evolution of the law.

     

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