Technological Parameter Analysis And Drill Bit Structure Optimization Of Reverse Circulation Drill Rig

The green construction of subway should follow the progress of social science and technology.The basic principles of "green" and "sustainable development" are realized by the optimizing the structure and process parameters of mechanical equipment.As a large pile foundation drilling equipment in subway station,the reverse circulation drilling rig which is also prone to rock debris blocking phenomenon and other faults.Currently,the degree of drill bit serialization and normalization is insufficient,so a kind of drill bit is required to increase stratum adaptability and high drilling efficiency.It took the pile foundation construction of subway station as engineering background.The results show that the drilling rate is the main factor affecting drilling efficiency and drill wear.Increasing the drilling rate of silty clay layer and fine medium sand layer to 2m/h can improve the drilling efficiency.Reducing the drilling rate of pebble layer and increasing the water consumption can increase the possibility of drill wear,drill pipe sticking and enhance the effect of borehole wall protection.Two kinds of Artificial Neural Network prediction models were established according to the drilling parameters of pile foundation,the prediction of drilling condition is realized by adjusting the inverse weight and optimizing the prediction effect of the model.The predicted results show that the average absolute error of drilling parameters of No.10,No.19 and No.20 king-piles is less than 5%,but the average absolute error of No.28 king-pile is more than 5%,indicating that the drilling condition of No.28 king-pile is abnormal.This is consistent with the drilling condition of the construction,the correctness and effectiveness of the two prediction methods are verified from practical project.A drill bit model based on the three-wing drill bit of a reverse circulation drill was established,and the dynamic drilling process of the drill bit was explored by using finite element numerical simulation.It is found that the average equivalent strain of the drilled stratum increases with the drilling time,the average equivalent strain rate was calculated to compare the drilling efficiency of different strata,the drilling effect and efficiency are different greatly,but the efficiency of pebble layer is low.The structure parameters of the drill bit model were optimized by uniform design method,the influences on drilling was explored by changing the structure parameters and drilling rate of the drill bit model to improve the drilling efficiency in the pebble layer.The equivalent strain rate equation is obtained by regression analysis of the simulation results,and the optimum drilling efficiency model is obtained by using this equation,the tip angle of drill bit is 45°,the angle between the drill tooth and drill boom is 45°,the drill tooth diameter is 65 mm,and the rotation speed is 10 rad/s.In order to improve the durability of drill teeth and reduce the wear of drill teeth,on the basis of the single-tooth simulation,the 3D printing technology was used to assist the design and carry out the mechanics experiment of the drill bit model.After pretreatment the outside machined single-tooth metal model,the loading force was applied to drill teeth model by Material Testing Machine,the strain of single tooth varying with loading force was studied.The mechanics experiment results are consistent with the simulation results,and the optimum durable drill tooth model is obtained,the tip angle of drill bit is 60°,the angle between the drill tooth and drill boom is 67.5°,the drill tooth diameter is 12 mm.The main factors affecting drilling efficiency were studied through on-site data analysis according to the established prediction model.The special drilling condition can be judged to reduce the potential risk.The dynamic process of drill bit drilling into different strata was simulated,the structural parameters of drill teeth were optimized in order to improve the drilling efficiency of pile foundation.On the basis of single tooth simulation,the mechanical experiment of drill bit model was studied.The established durable drill tooth model provides a theoretical basis for the industrial application of pile drilling equipment.