Study On The Weakening Law And Early Warning System Of Improved Soil In Coupling Field

Gravity pier structure in the northern plain river network area has a very wide range of applications,the conventional design is mostly used to throw fill 10 ~ 100 kg of stone as a wall behind the decompression prism,in order to effectively reduce the wall behind the soil pressure,but the amount of stone required is larger.In recent years,the country is paying more and more attention to ecological protection,and the restriction on quarrying has led to a shortage of stone and a significant increase in price,which has led to difficulties in the implementation of the traditional design of the stone prism in the engineering process.Due to its low price and good mechanical properties,modified soil has been widely used in road and construction projects,while water conservancy projects have fewer applications due to the influence of the endangered water environment.In this paper,an in-depth study on the application of improved soil in quay engineering is carried out using a combination of indoor tests,numerical simulations and field prototype experiments to explore the feasibility of using improved soil as a decompression prism material behind gravity quay walls.On this basis,the early warning threshold of soil damage was established and the corresponding safety warning system was constructed.The main research contents are as follows:(1)Experimental research on the basic physical and mechanical properties of improved soilsThe study selects representative cement and lime as the improved cementitious materials for the in-situ soil,and obtains the physical properties of the improved soil under different mixing conditions.Based on the physical test methods of unconfined compressive strength,consolidation undrained shear and permeability,the variation rules of compressive and shear strength and permeability coefficients of cement and lime soils with the admixture of cementitious materials,dry density,moisture content and maintenance age were obtained,the correlation between compressive strength and internal friction angle,cohesion,permeability coefficient and other indicators were analysed,and the correlation regression equation was established.(2)Study on the weakening law of improved soil under different field conditionsFirstly,the weakening law of improved soil under the action of single stress field was studied by fatigue performance test,and the changes of fatigue damage strength and fatigue life of improved soil were clarified with respect to the amount of cementitious materials and the age of maintenance,and the three-parameter power function mathematical model of fatigue life with stress amplitude and fatigue stress was established,and the correlation of compressive strength with fatigue damage strength and fatigue life was analyzed.Secondly,based on Comsol software,the deformation law and overall stability of different fillers under the action of coupling field are simulated and analyzed,the trend of change of stability safety coefficient of improved soil fillers is clarified,and the damage threshold of fillers under different working conditions is obtained.(3)Research on the safety warning system of improved soilThe ultrasonic testing of improved soil specimens before and after damage was carried out to obtain the variation of wave velocity of improved soil with respect to the amount of cementitious material admixture,dry density and curing age,and the relevant regression equation was established to clarify the response characteristics of wave velocity of different improved soils before and after damage under different working conditions,thus establishing the link between damage threshold and wave velocity.The results of SEM electron microscopy and XRD diffraction studies show that the macroscopic appearance and microscopic shape of improved soil with cement dosing less than 6% and lime dosing less than 8% are more obvious,while the damage characteristics of improved soil with dosing greater than this amount are extremely small.(4)Field application researchThe field prototype research was carried out based on intelligent means.Firstly,through the system platform built by the network,the basic parameters such as temperature,moisture content,earth pressure,deep horizontal displacement,settlement,pore water pressure,stratified vertical displacement and groundwater level of the improved soil filler were obtained in real time;secondly,they were correlated and analysed with the fluctuation parameters obtained in the field;finally,the structural damage threshold of the improved soil obtained by the finite element software was input into the platform as the basis of multi-level warning,and based on this,the The early warning system for improved soil fill was constructed.