Model Test Study Of Mud Thixotropic Controllability For Pipe Jacking

Pipe jacking construction technology has been being used in the construction of urban pipeline network widely,Despite the advantages of pipe-jacking construction,many problems still exist such as pipe-soil friction,Especially after the drag reduction by grouting,launching construction would be more difficult for some reasons,and resulting in inconvenience construction,So further study of pipe-jacking construction technology is of very great significance.Based on the study of mixture ratio,performance and mechanism of thixotropic slurry bentonite on several pipe-jacking construction projects,looking for a new method for friction reduction through model test study.Major research includes:1.By reading the relevant literature,pipe-jacking construction technology and construction process has been well understood.Combining pipe-jacking construction technology and the analysis of the application of thixotropic slurry in pipe jacking construction,different ratio of thixotropic mud in different projects making good effect of drag reduction,In the current project,friction can be controlled in 1Kpa,least or to 0.3Kpa by using mud drag reduction method.Obviously,slurry ratio modification plays a significant drag reduction role.While,more modification of thixotropic slurry ratio might work to the contrary.2.Study on mud properties of bentonite.Through the study,clarify the function of bentonite slurry and its applications in other fields.Construction of pipe jacking applied to sodium bentonite,When thixotropic mud formed in the pipe,pipe-jacking by buoyancy,efficient unit weight becomes smaller,of which the drag reduction is the best.This article summarized the application of thixotropic slurry in different projects,especially on the thixotropic slurry ratio,provide with adequate preparation for late-stage study.3.Study on slip ratio.Through comparative study between several mud proportion,performance test shows the appropriate choice of mud,Ratio of bentonite:CMC: soda: water=10:0.11:0.87:90,ratio of this mud,viscosity,water loss performance to achieve a reasonable requirement,and reflect good thixotropy,theoretically can achieve a better drag reduction effect.4.Manufacture of pipe model.Similar model studies of the theory of learning dimensional analysis method and the analysis method of model test and similarity principle,understand the basic concept of similarity theory,the properties of model materials and their impact on test results.More rational the material is selected,the conclusion of model test would be more accurate,but there is no absolute ideal material.We are going to make pipe through above way.5.Pipe testing the selected thixotropic slurry,analyzing the raw data of experiment,drawing diagram of the relation between the time and the average frictional resistance of tube,Through experimental analysis draw conclusions using this experiment of thixotropic slurry ratio,measured average pipe jacking resistance in0.264~0.422 Kpa,This ratio of slurries plays a good drag reduction effect.As the mud time stagnant growth,resistance increases gradually,once this maximum friction is overcome,average friction after growth has decreased over time,stability within a small area.6.Applying new method to activate mud thixotropy which reduces the pipe-soil friction.By using physical method of vibration,mud was still the selection of an appropriate ratio,the testing process,stalled for too long of mud,in the case of vibration,cut thin,thixotropy is activated,thereby reducing pipe-soil friction.Using concrete vibrator drive vibration within the drop pipe,compared to reduce vibration the measured average skin friction by one-fourth for the first time by this method to achieve the initial effect.