Research On Safe Construction Technology Of Curtain Grouting In Water-rich Tunnel

The excavation of deep buried tunnel with rich water can easily result in inrush of water,instability of the working face and excessive displacement of the supporting structure,etc.How to achieve fast and safe construction under this geological condition has aroused the continuous concern in the engineering community.Based on the practice of zhengpantai tunnel of jingzhang railway and relevant theories of fluid-solid coupling,this paper applies FLAC^3Dfinite element calculation software to explore how to take safety and economic construction technology into consideration in the high-pressure and water-rich stratum of pyroclastic rock.The content of this research is as follows:?1?Research on adaptability of advance grouting form?scope?.A total of five working conditions were established for comparison of grouting excavation,grouting around the arch wall,full-perimeter grouting,half-section curtain grouting,and full-section curtain grouting.Then the effects of different grouting conditions on the stability of tunnel surrounding rock are evaluated.Research shows that full-section curtain grouting and surrounding grouting can better meet the safety requirements of different seepage sections of the Zhengpantai Tunnel.?2?Research on parameters optimization of full-section advanced curtain grouting circle.On the basis of the full-section curtain grouting proposed in the preceding chapter,a typical section of zhengpantai tunnel is established.A total of five working conditions of different thicknesses of the full-section advanced curtain grouting reinforcement ring are synthesized.It is proposed that under the geological conditions of this dependent project,the thickness of 5 m is a relatively economical and reasonable parameters of the grouting circle.?3?Feasibility study for construction with water.Although the advanced curtain grouting scheme has a remarkable effect of water blocking,the borehole grouting and tunnel excavation interfere with each other in time and space dimension.This paper analyzes the displacement,stress,and seepage fields of surrounding rocks?three-step excavation?at five different water levels in a water-rich tunnel.The main criterion for the instability of surrounding rocks is the sudden change in displacement.Verify the feasibility of constructing a drainage hole on the palm surface to drain water and reduce pressure in advance,excavate the water forcibly through the gushing section,and then use radial grouting to stop the water.The head range suitable for water-bearing operations during the construction of the Zhengpantai Tunnel is clarified.