Study On Synchronous Grouting Reuse Of Shield Muck In Silt Stratum

The excavation of strata during the advance of the earth pressure balance shield machine in stratum would discharge lots of shield mucks.Those shield mucks will not only occupy the construction space and effect the construction schedule,but also consume a large amount of manpower and material resources to deal with shield muck,which results in huge waste of resource and great damage of city environment.At the same time,in order to control the stratum settlement caused by the shield tail gap,the synchronous grouting is needed during the shield tunneling boring,and the preparation of synchronous grouting slurry requires a lot of raw materials.The researches on the reuse of shield muck in synchronous grouting can not only save the cost of materials,but also alleviate the problem of resource waste and environmental damage.Based on this,this paper studies the influence of the mixture of shield muck on the performance of grouting material and its internal mechanism through a large number of laboratory tests,and a scheme of synchronous grouting reuse of shield muck in silty soil stratum is put forward.The main results of this study are summarized as follows:(1)The slurry performance of synchronous grouting material was summed up as fluidity,stability and strength,and the corresponding test methods were put forward:Considering initial value and time-lapse loss of fluidity indexes,the fluidity of the slurry is measured by consistency test,slump test and flow cone test.The stability of slurry includes material stability and volume stability,measured by bleeding test and consolidation shrinkage test.The strength index consists of short-term strength and long-term strength,tested by setting time test and compressive strength test.(2)The influence law and internal mechanism of the slurry performance caused by the mixing of shield muck were proved.The influence of the amount of shield muck on the performance of the slurry was obtained by the way that different raw materials were mixed into the grouting materials: 1)The fluidity and strength of shield muck mixed with fly ash have adverse effects,and the stability of shield muck is slightly improved;2)The fluidity is improved by adding shield muck into bentonite,and the strength is unchanged basically,but the stability is weakened greatly;3)The stability and strength of grouting materials are improved by adding shield muck into fine sand,but the fluidity is seriously lost.The main reasons for the change of fluidity is the influence of muck on the water content and the particle agglomeration ofgrouting materials,and the main reasons for the change of strength is the influence on the compactness and the toughness of block.(3)A scheme of synchronous grouting reuse of shield muck is developed.The improvement schemes of slurry performance were improved based on the understanding of the change mechanism of slurry performance,which is increasing the water cement ratio when the flow performance is poor,and increasing the cement dosage when the strength performance is not enough.Based on this,the mixture ratio scheme of muck reuse was obtained by optimizing and adjusting the mixture ratio of slurry.The feasibility of using shield muck as aggregate was demonstrated by XRD and SEM micro analysis,and the test results show that the muck is more conducive to the hydration than the fine sand.Finally,the engineering value of the reuse scheme of muck is described.The reuse scheme can save about 30% of material cost,which is good for resource recovery and environmental protection.