Study On Mechanism And Influence Factors Of New Curing Agent For Strengthening Soft Soil Of Marine Facies

In recent years,more and more land resources are needed for the expanding construction scale of Jiangsu coastal areas.However,the high quality land resources are limited,which needs it takes advantage of the widespread Marine soft soil with the characteristics of high water content,high liquid limit,low density,low strength,high compressibility and high sensitivity.In the experiment,a new type of curing agent with the characteristics of flash setting and early-strength,high concretion rate with high water-cement ratio was found,which is suitable for curing the Marine soft soil.Further studying on the curing effect and mechanism of new type curing agent curing chlorinated marine soft soil with high moisture content and a certain amount of organic matter is of great significance to guide the engineering practice and promote the application of new curing agent.In this paper,the content of organic matter and chloride were artificially adjusted by adding sodium humate and chlorine salt,and by adding humic acid and fulvic acid to alter the composition of the organic matter in dried Marine soft soil,and the new curing agent was used to curing the soil.Chemical analysis,reinforcement and mechanical tests were carried out.And the microstructure of the solidified soil with new soft soil was studied by scanning electron microscope.The following main achievements and conclusions are obtained:Through the analysis of the hydration reaction mechanism and hydration products of the main components of the new curing agent,and the hardening mechanism of the newly solidified soil was verified by experiments,which is the new type curing agent's dissolution and hydration,and then proceeding ion exchange and aggregation effect.Then a hard coagulation reaction occurred.Finally,the skeleton structure system of the new curing agent-soft soil was formed,and the carbonation reaction of calcium hydroxide had further enhanced the strength of the new curing agent.The effects of organic matter content,organic matter composition,moisture content,chlorine content and curing age on the strength of new curing agent were studied.The researches shows that: The effect of organic matter on the solidified soil has a relative critical value.When the content of organic matter exceeds the relative critical value,the rate of reduction of solidified soil strength will decreases significantly.The furic acid is more acidic than humic acid and has a greater impact on solidified soil.The increase of moisture content will lead to the "lag" of organic matter to the adverse effect on solidified soil,and the intensity decreases with the increase of moisture content.After the content of chlorine salt in soft soil exceeds the range of weak saline soil,the strength of solidified soil will be greatly reduced,and the higher the chloride content is,the slower the strength will increase with the age.The influence mechanism of organic matter,moisture content and chlorine salt on the new curing soil was analyzed.The results show that: The organic matter prevents the hydration of the new curing agent by adsorbing the surface of it to reduce the strength of the solidified soil.The humic acid in organic matter affects the strength of solidified soil through decomposing and corroding the hydration products of new curing agent.Increasing the moisture content,on the one hand,makes the hydration products of new curing agent distribute more uniformly in the soft soil,on the other hand makes the solidified soil porosity improve further,which has a double effect on the strength of the solidified soil.A small amount of chlorine salt indirectly enhances the strength of the solidified soil by inhibiting the dissolution of sulfate.Once the content of chlorine salt reaches the range of weak saline soil,it is mainly dissolved in the form of calcium chloride,resulting in a large porosity of the solidified soil and reducing the strength of the solidified soil.The relationship between quasi-water-cement ratio and unconfined compressive strength was obtained by fitting.The range of recommended values of slurry water ash ratio in different moisture content of the original soil was given.The condition and the corresponding formula of curing agent were put forward to be applied to the deep mixing method and high pressure jet grouting method in construction,and the applicable construction technology process was given too,which provides reference for the engineering application of new curing agent.