Experimental Research On The Effect Of Load And Chemical Constituents On The Mechanical Properties And Meso-structure Of Soft Soil In The Reclamation Area

Land reclamation for the purpose of port,wharf,urban construction and industrial land is characterized by large land reclamation area,fast reclamation speed,heavy load and so on;it can fundamentally change the physical and chemical environment of the soft soil at the land reclamation area,as a result of which,the macro-mechanical properties and meso-structure of soft soil is also changed.It is an important foundation for engineering construction to realize the impact of land reclamation engineering on soft soil characters.This paper,with the soft soil at the land reclamation area in Qinzhou and Fangchenggang as the object of study,from the two aspects of macroscopic mechanics and meso-structure,the effect of reclamation engineering on soft soil character is studied systematically.The main research work and results are as follows.1)Environmental disturbance analysis and simulation device developmentThe effect of reclamation engineering on the physical and chemical environment changes of soft soil is multifaceted for the purpose of port,wharf,urban construction and industrial land.From the viewpoint of geotechnical engineering,there are fundamental changes the two aspects of the cover load and the chemical field of pore water of soft soil.The indoor simulation device,"a soil soaking load linkage device",was developed to simulate the change of the load and pore water chemical composition in the soft soil of reclaimed land.The device is used to simulate soft soil cover load and pore water chemical composition in reclamation area,obtained artificial soft soil imprinted with the trace of cover load and pore water chemical composition.2)Experimental researchBased on the experimental study of the physical mechanical properties of artificial soft soil,the effect of load and pore water chemical composition CaC+and Mg2+ on change mechanism of soft soil characters is revealed.The conclusions are as follows:①The void ratio of artificial soft soil decreases with the increase of load,and decreased slightly with the increase of Ca2+ and Mg2+concentration.②The compression coefficient decreases with the increase of load,Ca2+ and Mg2+ concentration.③The adhesion force increases with the increase of load,Ca2+ and Mg2+ concentration.④The angle of internal friction increases with the increase of load and increases slightly with the increase of Ca2+ concentration,but the change is not obvious with the increase of Mg2+concentration.⑤ With the combined action of the load and chemical composition,there is one coupling effect on artificial soft soil between the load and chemical composition.The coupling effects of void ratio,compressibility,cohesive force and permeability coefficient are evident,the coupling effect of internal friction angle is weak.Based on the study of artificial soft soil SEM test and MIP test,the effect of load and pore water chemical composition Ca2+ and Mg2+ on meso-mechanism of soft soil characters is revealed.The conclusions are as follows:①The effect of the increase of load and Ca2+ and Mg2+ concentration on soil particle roundness,average equivalent particle diameter and fractal dimension of particle projection contour is not obvious.②Load has a certain degree of influence on particle arrangement orientation Angle,particle arrangement orientation angle(The Angle of the horizontal direction)decreases with the increase of load,but influence on particle arrangement orientation angle is not obvious with the increase of Ca2+ and Mg2+ concentration.③The effect of load and Ca2+ and Mg2+ concentration on pore average roundness is not obvious.④The pore diameter decreased with the increase of load and Ca2+ and Mg2+ concentration.3)Theory analysisIt is found that the pore ratio becomes smaller and the bonding strength increases with the load.With the increase of load and Ca2+ and Mg2+concentration,a portion of Ca2+ and Mg2+ precipitation crystallization come into being the cementing material,which resulted in the increase of the cementing material,the cementation bonding between particles enhanced,and the bonding strength increased.There is extremely obvious consistency between the macroscopic and mesoscopic scale,the macroscopic scale is the concrete quantification of mesoscopic scale.Under the maximum load of 180kPa,the change of the shape and size of the soil particles is not obvious,and the soil particles are mainly displacement,rearrangement,and the pore size of soil becomes smaller.The chemical composition Ca2+ and Mg2+ concentration increased,a portion of Ca2+and Mg2+ precipitated crystals to come into being cementing material,which enhanced the cementation of soil particles.There is correlation between artificial soft soil macroscopic mechanical properties and mesoscopic structure parameters.There is obvious correlation between the compression coefficient,cohesive force,the permeability coefficient and mesoscopic structure parameters.There is a certain degree of correlation between internal friction angle and microstructure parameters.