Underwater Excavation Test And Numerical Simulation Of Reverse Circulation Drilling Tool For Deep Foundation Pit

In municipal engineering,the excavation of a deep-pit excavated water-rich pebble stratum has always been a difficulty in engineering construction.The groundwater recharge ability of this stratum is strong,the traditional dry excavation method is difficult to implement,and the loss caused by precipitation is huge,even To threaten the safety of surrounding buildings,in order to protect the water resources,it is a brand-new attempt to apply the jet reverse circulation device to underwater excavation of deep foundation pits.Although this construction method technology has not yet fully matured,it has the advantages of flexibility,low energy consumption,low cost,safety and environmental protection,etc.It is the main trend of underwater excavation in the future.Based on the construction of the foundation pit project of Yongdingmenwai Station of Beijing Subway Line 8,the design and simulation of the jet device for the underwater excavation of the jet reverse circulation device applied to the deep foundation pit pebble stratum are studied.The main research contents are as follows:(1)According to the site's geological survey report,the selection of the working pump and the parameter design of the jet pump were carried out for the reverse circulation jet device with a pebble particle diameter of less than 10 mm in the foundation pit.The field experiment proved that the reverse circulation jet device can The solid particles in the foundation pit are pumped from the bottom of the pit to the surface and 6.7 cubic meters of solid particles can be extracted per hour.(2)The finite element software FLURNT 15.0 was used to simulate the flow field of the solid-liquid mixture in the 15 m submerged jet pump.Under the condition of fixed flow and keeping the throat diameter unchanged,by changing the single variable method,the area ratio of the four factors affecting the efficiency of the jet pump,the throat distance,the aspect ratio and the diffusion angle progression were numerically simulated.The optimal area ratio ranges from 10.2 to 11.2,the optimum aspect ratio ranges from 4.7 to 5.3,and the optimal diffusion angle ranges from 5.5°to 6.7°.(3)Orthogonal tests are used to determine the parameters within the optimal parameters,and the influence of each parameter on the jet pump efficiency is obtained.Through orthogonal test data analysis,the area ratio has the highest influence on the efficiency of the jet pump,followed by the length-diameter ratio,and the diffusion angle has the lowest impact on the efficiency of the jet pump.Finally,the parameter ratio that maximized the efficiency of the jet pump was achieved,resulting in a 4.5%increase in efficiency of the jet pump.