Study On Grouting Strengthening Technology Of Fine Silty Sandy Layer

Compaction silty sandy in the state of in situ has the structure close,the density is high,the permeability is good characteristic,but when the occurrence of the free surface,will appear the collapse phenomenon.The grouting reinforcement method is usually used to deal with the above problems,but for cement based grouting reinforcement materials,there are particles in the slurry,which are difficult to diffuse under the infiltration of sand,which can not be well penetrated into the soil,and the grouting quality is difficult to guarantee;However,the chemical grout has many problems,such as high viscosity,non adjustable condensation,low strength,poor durability,easy pollution and high price,which is not conducive to the reinforcement of fine sand layer.In order to overcome the shortcoming of grouting in sand stratum,solve the problem of low strength and stability,it is necessary to develop a new type of grouting material for grouting,grouting materials should be good groutability in the fine sand layer,and to improve and enhance the stability of the strength of the formation,at the same time,the economic application of feasible technical requirements.In view of the above problems,according to the engineering characteristics and grouting ability of fine sand,this article developed a composite chemical slurry(hereinafter referred to as AG slurry).The influence factors on the properties of slurry were investigated by using L9(34)orthogonal and single factor test,and discussed the effects of slurry incorporation and moisture content on the physical and mechanical properties of the consolidated sand consolidation.Developed a set of grouting simulation test device.With this device,AG slurry is used as grouting material and silty sand as the injection medium.The influence factors of slurry diffusion radius and intensity of injected body under different grouting pressure and grouting volume are studied.The contents of the study and the results obtained are as follows:1)Based on the analysis of the concept of injectability of fine sand layer,the influencing factors and the evaluation criteria,and the physico-mechanical properties test of fine sand performed on this basis,the fine sand granules have fine gradation and low permeability.When grouting in the formation,it is difficult to inject into the fine sand formation to find the larger particle size of the cement particles;chemical slurry with smaller particle size can be injected.Based on the analysis of the concept of injectability of fine sand layer,the influencing factors and the evaluation criteria,and the physico-mechanical properties test of fine sand performed on this basis,the fine sand granules have fine gradation and low permeability.When grouting in the formation,it is difficult to inject into the fine sand formation to find the larger particle size of the cement particles;chemical slurry with smaller particle size can be injected.2)The orthogonal test of AG slurry was carried out to get the influence rule of main agent AG,initiator AP and water dosage on the gel time,apparent viscosity and plastic strength of AG slurry,and the optimized combination of AG slurry was obtained;The rheological properties of the slurry can be studied by single factor control test,and it is found that the rheological properties of AG slurry can be divided into approximate Newtonian fluid phase,pseudoplastic fluid phase and shear expansion phase.;The apparent viscosity mutation time of the slurry increases first and then decreases with the increase of the main agent AG,and decreases with the increase of the initiator.3)According to the anti-pressure,shear and tensile tests for silty sand grout reinforcement by AG slurry,the incorporation of AG slurry can effectively improve soil physical properties,The physical and mechanical properties of powdery sand are not affected by the curing age,and the mechanical properties are influenced by the amount of AG slurry and water content.The greater the amount of AG slurry is,the lower the water content,the higher the strength of the consolidation body,and vice versa.4)Developed a new type of experimental device capable of simulating soil simulation and grouting process simulation.It can realize grouting simulation test under different grouting conditions of different soils,different combinations,different filling and different groundwater conditions.It can obtain the diffusion of slurry and the change of related parameters in the process of grouting and detecting the spread of the slurry,and then provide guidance for practical engineering design and construction.5)Application of permeation grouting test device,the sand grouting using AG slurry and sand injection through pressure control and flow control,cement slurry is difficult to get into the fine sand,in the same situation,the permeability of AG slurry than ordinary cement slurry have a large effective reinforcement range,grouting effect is good in the silty sand layer.6)The diffusion regularity and consolidation strength of AG slurry in fine sand formation are studied: The more the grouting quantity is,the more regular solid form is,the greater the volume is;The larger the grouting pressure is,the larger the transverse diffusion diameter is,the deeper the grouting reinforcement is;Under the condition of the same grouting pressure and grouting amount,the strengthening strength of the grouting of the solid is basically uniform,and the mechanical properties are relatively stable;In the same stratum,the AG grouting is used,the greater the grouting pressure,the higher the strength of the injected body;and the grouting amount has no obvious effect on the strength of the injected body.7)Based on the application of tunnel engineering of changhe avenue in binhe new area of yinchuan,it is verified that AG slurry is feasible and effective in grouting in fine sand formation,to a certain extent,the design and test purpose and effect are achieved.