Stability Analysis Of Shaft Excavation Of Adjacent Reservoirs Under Seepage-stress Coupling Action

With the development of economy and society,there are more and more projects involving geotechnical excavation at home and abroad.Due to the relatively complex and diverse engineering environment,more attention should be paid to the design,construction,safety evaluation and stability analysis of such projects.At present,urban water consumption is increasing.A water diversion project is a powerful measure to solve the contradiction between urban water supply and demand.The underground shaft pumping station adjacent to the reservoir has become a new type of pumping station,and it is also a necessary means to obtain the deep quality water source in the water diversion project.The excavation of shaft adjacent reservoirs is the foundation of underground pump station,and the construction condition of this kind of project area is complex and the groundwater seepage is very rich.Due to the influence of mechanical disturbance in the excavation process,the seepage field and stress field are complex and changeable,which have a direct impact on the stability of shaft excavation.Taking the water diversion project from Yellow River to LinxiaZhou as the background,take its the underground shaft pumping station adjacent to the reservoir as the research object.Through theoretical analysis,numerical simulation and analysis and comparison of measured data,study and analysis the stability of shaft and the distribution of seepage field and stress field in the construction process under the seepage-stress coupling effectinfluence,and summarize the law of shaft excavation deformation.The main research contents and results are as follows:(1)Based on FLAC3 D calculation software the model is established,the process of shaft construction of under different excavation conditions the change of seepage field,stress field.The seepage velocity and seepage flow rate increase with the increase of excavation conditions,and the drainage should be timely and reasonably conducted in the condition of serious seepage phenomenon,and the seepage field and stress field of the shaft are U-shaped distribution;(2)The horizontal deformation law of the wellhead and the shaft wall soil mass under various excavation conditions is analyzed.The deformation of the wellhead soil mass first increased and then decreased with the increase of excavation depth,and the maximum horizontal deformation of the wellhead is 10.40 millimeter.The maximum horizontal deformation of shaft wall is 12.33 millimeter.In addition,it was found that the shaft shaft with a depth of 0 to 15 meter had a large deformation,and the shaft shaft with a depth of 15 meter to 29 meter had a small deformation.Therefore,soil support should be strengthened in the first 15 m shaft wall section;(3)Analyzes the mechanical characteristics of shaft support structure and three support schemes.The supporting structure has effectively played its supporting role and reduced the deformation of the vertical shaft towards the void surface.The stress extreme value of thesupport structure conforms to the standard,which verifies the rationality of parameter setting.The first scheme is the most economical one with obvious support effect;(4)Based on the actual monitoring results of the deformation of the wellhead soil in the field construction process,the relationship between the deformation of the wellhead soil and the excavation depth is calculated,and the relationship curve is fitted.The simulated value and the measured value of the monitoring data are compared,and the measured value is slightly larger than the simulated value,but the overall change trend of the two values is roughly the same,which can better reflect the variation law of wellhead soil deformation in the process of excavation.