Optimization Of Slurry Parameters For Shield Residue Improvement In Sand-clay Composite Stratum

Slag improvement is one of the key technologies to ensure the smooth construction of earth pressure balance shield.Bentonite,as the most common clay mineral modifier,is widely used in soil improvement of earth pressure balance shield.At present,there is a lack of theoretical guidance on the use of mud modifiers for shield tunneling in sand-sticky composite strata,especially with the excavation of shield tunnels,the proportion of sandy soil and clayey soil in the stratum is constantly changing dynamically,and the parameters of mud modification are difficult to control.In addition,when the shield is located in the water-rich sand section of the sand-sticky composite formation,it is difficult to achieve a good improvement effect by using only bentonite,and the mud system mixed with bentonite and artificial polymers such as CMC or polyacrylamide,compared with pure bentonite mud,its performance is more superior,but it is difficult to degrade,and the generation of waste slurry is easy to cause environmental pollution.It is necessary to develop environmentally friendly mud materials suitable for water-rich sand layers.In view of the above problems,this paper studies the performance of bentonite mud and the characteristics of sand-sticky mixed slag through laboratory tests and obtains the shield tunneling mud construction of sand-sticky mixed slag under different sand contents through the satisfaction function-response surface method.parameters,and conduct the configuration of environmental protection mud for water-rich sand layers through indoor tests.The main research results are as follows:(1)Na-based bentonite mud with different concentrations was prepared,and the influence of mud concentration on mud performance was analyzed based on the Marsh funnel viscosity,fluid loss,specific gravity,colloidal rate,and p H values as research indicators,and the sandThe viscosity conforms to the mud concentration range of the formation muck improvement test.(2)According to the characteristics of sand-sticky composite formation,five kinds of sand-sticky mixed dregs with sand content were prepared,and the effects of sand content on plastic flow,shear strength and permeability of sandy-sticky mixed dregs were analyzed According to the law,the problems existing in sand-sticky composite formations under different sand contents are clarified.(3)Taking the slump and internal friction angle as the response value,and the sand content,mud concentration and mixing ratio of the sand-sticky mixed slag as the influencing factors,a quadratic regression equation for the response value was constructed through the CCD central composite test Using the model,the influence of sand content,mud concentration,and mud mixing ratio on the performance of muck under the interaction of sand content,mud concentration and mud mixing ratio are discussed,and the multi-response value is optimized in combination with the satisfaction function,and sand-viscose mixed formations with different content are obtained.Optimal shield tunneling mud construction parameters under sand volume.(4)Based on the analysis of mud properties under the action of single additive and compound additive,the ratio(mass ratio)of environmental protection mud for water-rich sand layer is determined as water: bentonite: guar gum: SA: CMS = 1000: 150: 0.2: 0.6:2.The improvement effect of environmental protection mud on the plastic flow,shear strength characteristics and permeability of water-rich sand layer slag under different mixing ratios was analyzed,and the mixing ratio of environmental protection mud in water-rich sand layer was determined to be 10%.