Experimental Study On Mechanical Properties Of Silty Soft Soil Modified By Industrial Solid Waste And Residual Soil

Various types of silty soft soil are widely distributed in our country.There are engineering characteristics such as high water content,high compressibility and low bearing capacity,which are extremely unfavorable to the construction of the project.Therefore,it is essential to strengthen the silty soft soil foundation before the construction.In this paper,the lacustrine silty soft soil is taken as the main research object,and three industrial solid wastes,including slag,fly ash and desulfurized gypsum,as well as engineering muck,are selected to modify the silty soft soil.The modified silty soft soil was prepared by orthogonal test,and the mechanical properties of the modified silty soft soil with different ratios were tested by water content and volume shrinkage test,unconfined compression test,direct shear test and penetration test,and the modified silty soft soil with the best ratio was optimized.In view of the modified silty soft soil samples with different amounts of modified materials,through the moisture content,unconfined compressive resistance and permeability tests of the samples under the condition of dry-wetting cycle,the influence law of dry-wetting cycle on the macromechanics of the samples was analyzed.USES the Fourier infrared spectrum experiment + EDS,SEM,energy spectrum analysis,X ray diffraction experiment,testing different curing age muddy soft soil specimen under the condition of modification of characteristics of microstructure and fabric material,reveal the slag,fly ash,desulfuration gypsum of silt soft soil modified curing mechanism,modification of silt soft soil subgrade as the research object,through the GEO-studio software simulation analysis of modified silt soft soil under embankment of construction and traffic load evolution regularity of stress and strain.Comprehensive experiments and numerical results above,the following conclusions:(1)put forward by slag,fly ash,desulfuration gypsum residue in collaborative project of new type of composite curing agent,the ratio of curing agent on the optimal(engineering: residue in slag,fly ash,desulfuration gypsum = 9:6:3:2),muddy soft soil moisture content of 14 d modified from the rapid decline in more than 38.7% to 5.1%,the volume shrinkage rate between 2.7% ～ 8.6% of 28 d,7 d after the unconfined compressive strength of 10.05 ～ 14.89 MPa.After curing for 7 days,the cohesive force reaches 305～341k Pa,the internal friction Angle is 62.96°～64.78°,and the permeability coefficient is3.99×10-8cm/s.All the mechanical indexes are significantly improved(2)the test analysis ZJ7 dry-wet circulation process,ZJ9 sample macro mechanical properties and microscopic pore structure characteristics,the results showed that with the increase of dry-wet cycles,the wet moisture content falling off,after four times of the dry-wet cycle reduced from 15% to 5%,its moisture content and unconfined compressive strength in the first two times after the dry-wet circulation can improve 15% ～ 25%,the third in the fourth dry-wet circulation started to fall and compressive strength under dry-wet circulation gradually after before;Under the action of four wetting and drying cycles,the permeability coefficient of ZJ7 group increased from 3.99×10-8cm/s to8.39×10-8cm/s and remained within the same order of magnitude,while the permeability coefficient of ZJ9 group increased from 4.40×10-7cm/s to 4.03×10-6cm/s,with a larger variation.The pore sizes of the samples ranged from 4.83 μm to 200μm,and the pore sizes were mainly about 36μm.The porosity ranged from 35% to 42%,and the porosity increased by about 13% after four cycles of wetting and drying.(3)through SEM and EDS,FTIR,XRD and other test,found that the modification of muddy soft soil as internal reaction activation of fly ash,silicon oxygen tetrahedron-Si-O-Si-dissolved,generate silicate and-Si-O-and will-Si-O-polymerization again after formation of hydrated calcium silicate,and hydrated aluminum silicate,hydrated silicate content aggregation form hydration products again,the final form of gel network,through XRD phase analysis of the main components in muddy soft soil modified zeolite,feldspar,alum stone,luster and aluminum phosphate gel material,etc,EDS and FTIR proved that the gel network was mainly C-S-A-H gel network and(C,N)-S-A-H gel network,and quantitatively proved the composition of the above substances from the element content.(4)Geo-studio software was used to simulate the evolution law of stress and strain of the modified silty soft soil subgrade during the filling process and under the action of traffic load.The calculation results showed that the maximum total stress of the modified material was 408 k Pa and the maximum settlement was 2.8mm after the completion of the two-layer filling.Under the action of traffic load,stress and strain of subgrade soil is mainly related to the driving speed and vehicle static load,the maximum total stress increase to 668.93 KPa,and stress concentration in the lower left and lower right corner of the confluence of silty clay layer and mudstone,settlement dramatically increased,but its in the axial load of 100 KN,128 KN and 157 KN is the measure of the settlement of the18.5 mm,the specification within the allowable range.