Exprimental Study On Static And Dynamic Characteristics Of Muddy Soil And Its Solidified Soil In Nansha,Guangzhou

In recent years,in the treatment of soft soil foundation such as silt and muddy soil,it is an effective way to improve the properties of the original soil by adding additional solidified materials,and it is widely used in the foundation treatment of large-scale construction projects such as buildings,highways,bridges and tunnels in the coastal area.At present,in the study of muddy soil and its solidified soil,on the one hand,due to the complex nature of muddy soil and the different causes of soil in different regions,the properties are quite different,and there are many kinds of solidified materials,so it is necessary to study muddy soil and different kinds of solidified materials in different regions;on the other hand,few scholars have systematically analyzed the material ratio and static and dynamic characteristics of muddy soil and solidified soil under different influencing factors.In view of the complex muddy soil formed by the river and sea alternation in Nansha area,Guangzhou,this paper uses the composite solidified material with cement as the main and lime-fly ash as the auxiliary to solidify the original soil sample.Through a series of routine geotechnical tests,static triaxial tests and dynamic triaxial tests,the static and dynamic characteristics parameters of the muddy soil and its solidified soil are studied,and the better composite solidified material ratio is determined,the influence of the content of solidified material,curing time,initial moisture content,confining pressure and vibration frequency on the static and dynamic properties of solidified soil is analyzed.The main contents and results are as follows:（1）A series of routine geotechnical tests and static dynamic triaxial tests were carried out on the original muddy soil samples.The mechanical parameters such as the basic physical properties,static dynamic strength,dynamic elastic modulus and damping ratio of the original soil samples were obtained,which were consistent with the characteristics of high moisture content,high void ratio,low shear strength and easy deformation of the muddy soil.（2）The static triaxial test of solidified soil shows that the addition of lime-fly ash can improve the static strength of the pure cement stabilized soil,and when lime-fly ash accounts for 50%of the cement content,the strength of solidified soil increases the most,which is the better proportion of the composite solidified material;at the same time,the increase of the content of solidified material,curing time and confining pressure can improve the static strength of solidified soil,and the increase of initial moisture content will reduce the strength of solidified soil,and the influence degree of the amount of solidified soil is largest among all factors.In the aspect of the characteristics of the stress-strain curve of solidified soil,when the content is 5%or less,the stress-strain curve of solidified soil is hardening type,and the plastic failure of the sample occurs,while when the content is 10% or more,the curve becomes softening type,and the brittle failure of the sample occurs.（3）Through the dynamic strength test,the dynamic strength curves of solidified soil under different factors such as the content of solidified material,curing time,initial moisture content,confining pressure and frequency are obtained,and the fitting analysis is carried out.It is found that the dynamic stress amplitude and the logarithm of failure cycle show a linear decreasing relationship;at the same time,the static and dynamic strength are compared and analyzed,and it is found that the influence of each factor on the dynamic strength of the solidified soil is similar to the static strength,but the dynamic stress amplitude is similar When the content of solidified soil is high,the dynamic strain of the sample will break suddenly and quickly under the action of dynamic load,and there is no sign of failure.（4）It is found that the dynamic backbone curve of solidified soil can be expressed by hyperbolic model,and E_dmax andλ_max values under various factors can be obtained by fitting the model.The expressions and corresponding parameter values of E_d/E_dmax-ε_d and λ/λ_max-ε_d normalized curves of solidified soil are given.Among all the factors,it is found that the increase of the content of solidified material can greatly improve the maximum dynamic elastic modulus of solidified soil,which can reach nearly 400MPa at the maximum;the increase of curing time can make the reaction of solidified material more thorough,the increase of confining pressure and frequency,slightly increase the maximum dynamic elastic modulus of solidified soil,while the increase of water content will significantly reduce the value of dynamic elastic modulus;at the same time,the influence of each factor on the damping ratio is opposite to that of the dynamic elastic modulus.