Study On The Influence Factors And Engineering Characteristics Of Marine Soft Soil Solidified With Chemical Method

Marine soft soils are widely distributed in the coastal areas and around the coastline,which are characterized by high water content,low permeability,high compressibility and low bearing capacity.However,the traditional treatment methods such as stacking and dumping will occupy a lot of land resources and affect the marine ecological environment.Based on this,chemical stabilization method was used to treat it in this study and the strength and stiffness of marine soft soil can be obviously improved.It is of great value and significance to realize the reuse of waste resources,energy saving and emission reduction.The engineering characteristics of solidified soil was studied by the chemical stabilization method.This study starts from the relatively single kaolin,and then goes further to the study on the solidification and engineering characteristics of the complex marine soft soil.This paper focuses on(i)the engineering properties of solidified soil and the stabilization of kaolin and marine soft soil with chemical method,(ii)the influence of salt and organic matter on engineering properties of marine solidified soil,and(iii)the constitutive model of marine solidified soil.The main work of this paper is as follows:(1)The influence of different admixtures on the strength and deformation characteristics of cement-silica fume-kaolin system was studied.The optimum admixture for improving the unconfined compressive strength of cement-silica fume-kaolin system is sodium hydroxide/calcium chloride.The stress-strain relationship of the solidified soil indicates that most of the solidified soil exhibits strain softening behavior.The relationship between secant modulus of solidified soil and unconfined compressive strength was established,which showed that the secant modulus of solidified soil increased with the increase of unconfined compressive strength.(2)The influence of different admixtures on strength and deformation characteristics of cement-silica fume-marine soft soil system is studied.It is determined that sodium hydroxide and plant ash can promote the unconfined compressive strength of cement-silica fume-marine soft soil system.On the basis of it,the optimum ratio of cement,silica fume,plant ash and sodium hydroxide was determined by orthogonal experiment,and the composite curing agent of marine soft soil was obtained.The X-ray diffraction(XRD)and scanning electron microscopy(SEM)were used to test the solidified soil.The XRD results showed that the addition of curing agent would lead to the decrease of the diffraction peak value of active clay minerals such as quartz and illite in the clay,which confirmed the occurrence of chemical reaction between curing agent and active clay minerals.SEM test results show that the hydration products with gelatinizing properties,such as calcium silicate hydrate and calcium aluminate hydrate,can cement soil particles to form soil skeleton structure,which can significantly improve the compressive strength of solidified soil and effectively resist the influence of external load.(3)Based on the characteristics of high salt content of marine soft soil,the influence of salt content on unconfined compressive strength of solidified marine soft soil was studied.It was found that salt content had a significantly negative effect on the strength of solidified soil.The loss of unconfined compressive strength was defined to express the influence of salt content on strength.On the basis of analyzing the mechanism of salt,the concepts of equivalent cement consumption and salt consumption index are put forward.The theoretical content of curing agent is equal to the sum of the actual content and equivalent consumption.The calculation model for unconfined compressive strength of marine solidified soil with different salt content was established by combining with the water-cement ratio calculation model.(4)The influence of organic matter on the unconfined compressive strength of solidified marine soft soil was investigated.The results showed that organic matter had a significantly negative effect on the strength of solidified soil.The strength loss was defined to characterize the influence of organic matter on the strength.The influence of organic matter on after-curing unit weight and after-curing water content of solidified soil was investigated.The expression of void ratio of solidified soil was obtained.The unconfined compressive strength calculation model of solidified marine soft soil with different organic matter content was established.(5)The expression of total stress-strain relationship in elastic stage,initial yield stage and softening stage of solidified marine soft soil was established.The experimental characteristics of triaxial isobaric consolidation and triaxial undrained shear of solidified soil were investigated.The final stress-strain models of solidified soil mainly depend on the compaction of particles and the damage effect of structure.By comparing the calculated values of the constitutive model with the measured values in laboratory,the results show that the constitutive model can better simulate the strain softening,hardening and dilatancy behavior of solidified soil during shear.Finally,the relationships between the initial structural yield stress,initial cohesive strength of solidified soil and cement contents were established by exponential function.