| The project of study in the context is the Lanjiayan tunnel of mian-mao highway in Sichuan, detailed introduces the principle and application of advance geological forecast technology; focus on the mian-mao road Lanjiayan tunnel complex geological conditions, through the comprehensive application of various kinds of advanced geological forecast technology, accurate forecast the geological situation, the Lanjiayan tunnel is obtained under different geological conditions and the advanced prediction method and the characteristics of judgment from the forecast results;Lanjiayan high geostress of surrounding rock in tunnel are analyzed in numerical simulation, obtained the primary support high geostress surrounding rock deformation and stress distribution, to guide the later work of Lanjiayan tunnel. This article main research content and the results have the following several aspects:1. This paper discusses the working principle of TSP203, geological radar, infrared ground water, technical parameters, and etc., and this paper introduces the advantages and disadvantages of the flat guide in advance and geostress measurement in advance geological forecast methods.2. In the research area near the Lanjiayan tunnel geological information, collecting and sorting the Lanjiayan tunnel project of regional geological data, detailed reading mian-mao road engineering design information, on the basis of those, and considering forecast technical personnel’s technical conditions, ownership, the scene of the applied condition of instruments and equipment factors, combined with the experience of similar projects in the region and the advantages and disadvantages of advance geological forecast method, choose a suitable advance geological forecast method in Lanjiayan tunnel of safe and reliable.3. Detailed discussed the Lanjiayan rich water and weak rock tunnel broken segments, lithological change section, high ground stress period of advance geological forecast method, the judgment mark of above four condition of the paragraph obtained.1) Rich water: TSP detection system features: the vertical and horizontal wave velocity ratio increases, the poisson’s ratio increases suddenly, shear wave reflection is stronger than longitudinal-wave, density and young’s modulus decreased; Electromagnetic wave characteristics of intermittent phase axis, radar wave amplitude is stronger, and there are multiple reflection phenomenon; Infrared field strength value mutation, larger more than the critical TVC.2) Soft and broken section: TSP detection system features: the shear and longitudinal wave velocity and poisson ratio is reduced, density and young’s modulus decreased; Electromagnetic wave characteristics of discrete event, radar wave amplitude is stronger.3)The lithological changes: on the basis of TSP such as long distance forecast, geological radar, and other key short advance geological forecast for advance geological forecast, lithological change of electromagnetic wave characteristics mainly considering the change of frequency, the strength of the signal.4) High geostress: rock tunnel Lanjiayan three main stress increases with the burial depth of the tunnel, σV linear growth, andσH>σh>σV,aximum principal stress value is 29.2 MPa, According to the stress ratio method the tunnel belong to high geostress. 4. In view of the high geostress Lanjiayan tunnel segment(K50 + 730- K49 + 730), using Flac3 d numerical simulation software, analyzed in different stress value, the deformation characteristics of surrounding rock, as the ground stress increases, the vault subsidence, and inverted arch uplift and horizontal convergence, all Lanjiayan high geostress section of the maximum deformation of rock tunnel is 103.46 mm, within the range of allowable deformation; Initial supporting stress distribution law of initial support of vertical stress at the wall is larger, the vertical stress of the vault is small, the level of the primary support to the stress in the arch is bigger, smaller wall place, for the compressive stress, and increases with the increase of geostress. According to the results of numerical simulation and monitoring found that high geostress Lanjiayan tunnel segment(K50 + 730- K49 + 300) large deformation will not occurred. The initial support stress distribution law show that the vertical stress of initial support is larger at the side wall, the vertical stress of arch crown is small, the horizontal stress of initial support is larger in the vault, smaller in the side wall,and both of them are compressive stress which will increase with the increase of stress. The distribution law of plastic zone of surrounding rock show that the shape is roughly circular and it will increase with the increase of stress. |
