Study On The Force Of Protective Cylinder In The Process Of Full Protective Cylinder And Tube

Problems such as broken pile,shrinkage and segregation occur easily in the construction of cast-in-place pile,which makes it difficult to guarantee the quality of the project.At the same time,the use of mud wall protection in the construction of cast-in-place pile will inevitably bring environmental pollution problems.Under the new situation of increasingly strict environmental protection standards,more requirements are put forward for the construction of cast-in-place piles.As a new construction method,the follow-up process of full protective tube is suitable for all kinds of strata.During the whole construction process,mechanical drive protecting cylinder is used to drill holes to ensure the quality of holes.During the drilling process,there is no vibration effect on the surrounding buildings,and the dry drilling method avoids the environmental pollution caused by mud wall protection.Therefore,under the background of the refined development of the construction of cast-in-place piles,the follow-up process of the full protective tube has a broad application prospect.This paper mainly studies the whole construction process of the follow-up process of the full protective cylinder from three aspects of theoretical analysis model test,engineering application.The theoretical analysis starts with the stress state of the shield and analyzes the two stages of drilling and lifting the shield.The drilling resistance is mainly the end resistance caused by the cutting of the soil at the end of the sheath and the side resistance caused by the friction between the outer wall of the sheath and the soil layer.The main resistance to be overcome in the stage of upper supporting cylinder is side resistance.According to the drilling force of the casing,the casing is divided into three parts₁、₂、₃,the stress state of each section of the sheath and the judging method of damage of the sheath based on the fourth strength theory are given.The model test investigated the influence of the drilling speed of the diameter of the reamer on the growth of the resistance plug at the total resistance end and the resistance side in sand layer.Through the analysis of the experimental results:The resistance of the casing is positively correlated with the drilling depth,the casing diameter.In the process of drilling,the height of the earth plug in the casing increases first and then becomes stable,The final height of the plug is positively correlated with the diameter of the casing.The increasing trend of end resistance and soil plug indicates that the accumulation of soil in the sheath increases the end resistance and results in the decrease of drilling efficiency.The drilling speed of the casing has little effect on the drilling resistance.However,with the increase of rotation speed,the change of resistance fluctuates greatly;the change range of the perpendicularity of the sheath increased.The influence of drilling speed on the final plugging height is not obviousThe engineering application is mainly based on the characteristics of the follow-up process of the full protective tube,and the application of this construction method in the construction of the interlocking pile with underground obstacles removal is summarized,including the solution of technical difficulties in the construction process.