Development And Experimental Research On New Soil Conditioner Materials For Sandy Pebble Stratum

Soil conditioning is one of the key technologies to ensure the smooth progress of EPB construction.There is still no good solution to the construction problems often encountered in the construction of sand-pebble stratum,such as high torque,pebble accumulation and water spewing.Study the new soil conditioner materials suitable for sand-pebble stratum is very important to expand the adaptability of EPB to different stratums.In this study,new soil conditioners were studied through theoretical analysis,laboratory experiments and field verification.The main results are as follows:(1)A set of foam half-life test methods and foam agent performance evaluation indicators are proposed.The factors influencing foam stability and commercial foam agent performance characteristics are studied,and the performance optimization indexes and evaluation methods of self-made foam agents are determined.(2)Six foam conditioners with different stability were obtained,and their half-life was between 10-60 min.In the winter,the Kraft-point of the foam conditioner can be reduced by adding diethylene-glycol-butyl-ether to the foaming agent.Comprehensively comparing the foaming performance,acid,alkali and salt tolerance of self-made foaming agent and commercial foaming agent stock solution and their effect in low temperature environment,it is concluded that self-made foaming agent is superior in all aspects.(3)The regularity characteristics of the effect of foam parameters on sand-pebble conditioning were studied,and the conditioning effect of foam stability on sand-pebble permeability was verified.The effects of different foam parameters on the fluidity,permeability and friction reduction of sand-pebble soil are summarized,and the effect of foams with "high stability,medium expansion ratio and injection ratio" on sandpebble is more suitable.(4)A new type of polymer thixotropic mud material was developed.A / B liquid was mixed to form thixotropic mud to solve the improvement problem of large-grained sand and pebble soil below the groundwater level.Combining the slump and permeability test results,the concentration and ratio of each component are preferably: 13wt% slurry: 20wt% N-thixotropic agent : 34wt% sodium silicate: 0.5wt% hydroxyethyl cellulose = 10 : 1: 2: 2.(5)The application effect of self-made foaming agent in Beijing Metro Line 19 and Line 8 project was verified.Combined with the results of laboratory experiments and field tests,a reasonable range of foam parameters suitable for reducing the cutter head torque in anhydrous sand pebble stratum and reducing the spewing frequency of the screw machine was obtained.The characteristics of the correlation of tunneling parameters are summarized,and the selection and parameter recommendations of sandy-pebble stratum conditioners are given.