Study On The Methods Of Water Gushing-out Tunnel Fore Geological Forecast And Prevention Measures

Along with transportation, water conservancy and other infrastructure focus gradually transfer to the extremely complex geological conditions and karst mountainous region of West-China, tunnels and underground engineering construction’ scale and difficulty increases exponentially, in terms of construction, we will face many challenges, particularly in the disaster management of water gushing-out the construction suffered can be called world-class engineering problems. According to statistics, water gushing-out caused by improper disposal accounted for 80% of the tunnel construction accident in our country, water gushing-out often lead to heavy casualties, economic losses and schedule delays, and some are even forced to cease or change the tunnel line. In addition, if the water gushing-out disaster cannot be governed effectively, environmental geological disasters will be easily induced, such as depletion of water resources, surface subsidence, and threat to social stability and economic development. So during excavation taking an accurate Advance Geological Forecasting in front of the tunnel face is of great significance to reduced construction accidents, ensured the safety of construction workers and the construction schedule. But people are the results of previous geological interpretation of the radar system is still of main man experience, lack of interpretation signs, often resulting in "a map of multiple solutions," so further study of the geological characteristics of radar adverse geological body, set up to interpret the results forecast a general rule, precision and accuracy to improve ground penetrating radar has a pivotal role.In this paper, using a gushing Daba Mountain tunnel project as example, through the analysis of a large number of tunnel prediction result, extract the general laws of geological radar spectrum in this paragraph rock; Combined with the results of this geophysical exploration of surrounding detected a general rule, abnormal gushing sections of the tunnel for the proposed special forecasting programs; according to the geological survey data of the tunnel, hydrogeological conditions in and around the tunnel site, combined with the actual characteristics of gushing, gushing occurred analyzed tunnel reasons; Gushing Water Treatment Measures proposed tunnel under the law of groundwater storage space and movement; Finally, according to comparative analysis of tunnel grouting were evaluated before and after the change Inflow treatment effect, the main results obtained in this paper include:(1) Discussed the detection process parameter values according to the geological conditions of the tunnel, geological radar and TSP detection principle.(2) Through a lot of tunnel prediction results of geological radar, for cracks and shale aquifer were analyzed to find out the general rule of ground penetrating radar to detect interpreted the paragraph, fissure segment: the more clutter reflection waveform amplitude changes, alternating phase, accompanied by diffraction, scattering and other phenomena; on the spectrum showed a high frequency(100MHz) based, wide amplitude, near frequency often accompanied by several small peaks. Watery section: electromagnetic wave propagation velocity is low, resulting in strong emission wave, sometimes produce diffraction, scattering phenomenon; the gray image electromagnetic wave amplitude than the full, rounded, often continuous visibility amplitude; as the water content increases, the radar frequency decreased by multimodal gradually shift to a single peak, on the spectrum images showed to low frequency(25MHz) mainly to isolate the spectral peaks form, gradually weakened in the high frequency part, the high frequency part has tended to disappear.(3) With a comprehensive prediction method TSP, ground penetrating radar and infrared probe combination of water at the abnormal gushing of the tunnel, compared to forecast the results of a comprehensive, proven basic wall rock behind the tunnel face: fractured joints, groundwater development, including water tunnel face a slight increased.(4) Through macro-geological conditions in the study area, topography, tunnels sudden gushing features and tunnel excavation revealed geological data, the results ahead of forecasts detection analysis research to identify the causes of sudden abnormal Blow Section of Tunnel: Tunnel in the body side rainfall, surface water rich, have adequate supplies of water; tunnel abnormal water inrush fold core of extruded sections in fracture zones, by tectonic stress, tunnel surrounding rock joint, fractured, groundwater enrichment offers a wide range of storage space; according to characteristics of surrounding rock tunnel face excavation revealed, through the surrounding rock fissures, communicate with each other better, to provide a groundwater migration pathway.(5) Based on the introduction sudden gushing water tunnel common methodologies and governance principles, identified books sudden gushing water tunnel "to block" approach, in combination with other tunnel project management experience, proposed the use of advanced curtain grouting method to manage The tunnel sudden gushing water section and grouting parameters. The use of cement-silicate slurry grouting the whole cross-section, the effective diffusion radius of grouting hole 2m, grouting initial pressure of 1.0MPa, the final pressure 2.0MPa, grouting plugging the effective range of reinforcement outside the excavation contour 5m, excavating face evenly arranged tricycle grouting hole spacing ring are 2m, a grouting length 15 m, every excavation 12 m, 3m remain as the next cycle grouting occluding disk, hole injection slurry injection volume 7.8m3. Inflow before grouting tunnel about 7000m3/d, after grouting tunnel water inflow of about 450m3/d, tunnel gushing disaster control effect is obvious, the validity of the use of advanced technology in the fractured section of curtain grouting of the tunnel governance sudden gushing water.