Study On The Evolution Law Of THCM Characteristic Parameters Of Stabilized Marine Clay And Its Constitutive Model

As the "Strategy for a Powerful Marine Country" and the "Marine Silk Road" proceed,marine clays on the coast and the near/far seas was "forced to work." Due to the high natural moisture content,high compression coefficient,low shear strength and low permeability coefficient,marine clays cannot be used directly for engineering constructions.There it needs to be reinforced before using as engineering structure.The cement reinforcement method is one of the most effective reinforcement methods.The evolution of thermo-hydro-chemo-mechanical(T-H-C-M)characteristic parameters of cement-reinforced marine clay is a key issue of its reinforcement effect.However,there have not yet been systematic studies on this issue.In light of this,the thesis adopted comprehensive research approaches,including laboratory test,monitoring test,numerical simulation and theoretical analysis,to explore the evolution law of the THCM characteristic parameters of stabilized marine clays under different conditions,such as cement content,curing temperature,and initial moisture content.Then,this study revealed the influencing law of multiple factors on THCM characteristic parameters.Meanwhile,the correlation law of THCM characteristic parameters of stabilized marine clays with multi-factors were systematically analyzed.Based on these studies,a damage constitutive model that can comprehensively and accurately reflect the mechanical properties of stabilized marine clays was derived.The main contents of this thesis are as follow:(1)The column test was introduced for the first time into the sample preparation and characteristic parameter monitoring for the stabilized marine clay.The evolution law of THCM characteristic parameters of stabilized marine clays with various cement content was obtained through monitoring tests.More cement leads to an increase of the product of the hydration reaction,thus leading to more dissolved ions in the pore solution.As a result,the peak conductivity(C)increases with cement content.Meanwhile,the process of hydration reaction consumes more water,which induces a decrease of the volumetric water content(H)and an increase of matric suction(H).Furthermore,the heat release due to the hydration reaction will increase the temperature of the sample.With the increase of cement content,more hydration products were generated and precipitated in the pores,which can decrease the permeability coefficient(H),and increase the strength(M),the anti-deformation ability(M),the overall stability(M)and the thermal conductivity coefficient(T).(2)This thesis revealed the evolution law of THCM characteristic parameters of stabilized marine clay at various curing temperature.A higher curing temperature directly increases the internal temperature(T)and accelerates the cement hydration and the selfdesiccation.As a result,more ions were released,which leads to a significant increase in the peak conductivity(C)and a less time to reach the peak conductivity.Also,high temperature accelerates the water consumption in the sample,which decreases the volumetric water content and increases the matric suction.Meanwhile,high temperature contributes the formation of hydration product,thus leading to lower porosity and denser structure.As a result,the strength,the anti-deformation ability and the thermal conductivity increase,while the permeability decreases.(3)The study determines the optimal construction moisture content(22%)of stabilized marine clay at which the unilateral compression strength(UCS)is the largest.The increase of moisture content directly causes the increase of volumetric water content(H)and the decrease of matric suction(H).When the moisture content is lower than the optimal moisture content,the increase of water content leads to the generation of more hydration product.As a result,the UCS(M),CBR(M),peak temperature(T),thermal conductivity(T),peak conductivity(C)increase,while the permeability coefficient(H)decrease.However,when the water content is higher than the optimal construction water,with the increase of water content,the UCS,CBR(M),peak temperature(T),thermal conductivity(T)decrease,while the permeability coefficient(H)increases.(4)The correlation law and correlation mechanism of the THCM characteristic parameters of the stabilized Marine clay showed that the hydration of cement led to the change of conductivity and internal temperature,leading to the decrease of the volumetric water content.On the other hand,the hydration products fill the voids,which leads to the change of the UCS,CBR,thermal conductivity and permeability coefficient.Considering the effect of cement content and curing temperature on the correlation law of the THCM characteristic parameters,the study revealed that the increase of cement content and curing temperature increase the hydration products that fill the pores.As a result,both the intersection of heat conduction coefficient and permeability coefficient,as well as the intersection of matric suction and UCS,were reached earlier.Based on the results,this study obtained the simultaneous deduction figure of THCM characteristic parameters of stabilized marine clay,and developed a theoretical prototype of multi-field performance interaction.(5)Based on the result of SEM test,the evolution of microstructure characteristics of stabilized marine clay was observed.It is found that the reinforcement mechanisms of the marine clay include hydrolytic hydration of cement,interaction between hydration products and soil particles(i.e.ion adsorption exchange and agglomeration,setting hardening,carbonation and hard setting reaction).Then,a structure model of stabilized Marine clay was established.(6)The stress-strain relationship of stabilized marine clay under different conditions is deduced and established.Based on these constitutive equations,a comprehensive damage constitutive model that considers multiple coupling behaviors,including temperature-time coupling,cement content-time coupling,water content-time,and curing temperature-cement content-time coupling model,was proposed.This model was implemented into solid mechanics module of COMSOL Multiphysics for simulating the stress-strain relationship of the stabilized Marine clay under different conditions.The simulation results are in good agreement with experimental data,which demonstrates the reliability of this model.