| Sea reclamation has become an effective way for coastal cities to ease the land scarcity while dredger fill used for land reclamation is the main way.The dredger fill can't be used for soil foundation directly because of its characteristics with low bulk density,large pore ratio,high water content as well as the low strength and so on.Therefore,it's important and practical for foundation soil treatment of sea reclamation project by the chemical curing agent on dredger fill reinforcement in order to improve the strength of dredger fill.The dredger fill of Hebei province Tangshan City Caofeidian sea reclamation region is taken as the research object and the polyacrylamide(PAM)and water glass(Na2SiO3)are taken as curing agents to design the P-N(PAM and Na2SiO3)solidification scheme.The physical and chemical properties of dredger fill were tested by the means of basic physical properties,particle analysis,compaction test,soluble salt analysis,groundwater quality analysis and XRF analysis.Additionally,by the means of triaxial shear test and unconfined compressive strength test,the deformation and strength characteristics of dredger fill before and after solidification were compared and analyzed,as well as the solidification effect evaluation of PAM and water glass on the condition of single doped or double mixed.Based on orthogonal test,the influencing degree to solidification effect of such factors as the proportion of PAM and water glass as well as curing age were analyzed,and the optimal curing condition was determined.With the help of fuzzy evaluation method,the comprehensive evaluation was obtained for solidification effect of PAM and water glass on the condition of single doped or double mixed.Furthermore,the microstructure characteristics of dredger fill before and after solidification were compared and studied,while the solidification mechanisms of dredger fill were revealed.The researches indicate as follows:(1)Caofeidian sea reclamation area dredger fill is silt,with chloride and sulfate of alkali metal as the main soluble salt,the alkaline groundwater quality,clay minerals as the main mineral composition,and belong to alkaline soil.(2)The unconfined compressive strength and shear strength index C,? of PAM single doped solidified dredger fill are positively related to the proportion of PAM and curing age.With the increase of PAM proportion and curing period,the triaxial stress-strain curves gradually transformed into strain softening from strain hardening.(3)The unconfined compressive strength and shear strength index C,? of water glass single doped solidified dredger fill show positive correlations with water glass proportion and curing period.With the increase of water glass propotion and curing period,the strain softening trend of triaxial stress-strain curves is increasing,thus the non-deformability and strength of solidified dredger fill are improved.(4)With the increase of curing period,the unconfined compressive strength and triaxial shear strength index C,? ofP-N(PAM and water glass)double mixed solidified dredger fill increase more,the triaxial stress strain curves are strain softening,shear strength and non-deformability are improved.(5)According to the fuzzy evaluation method,the comprehensive evaluation is made for the solidified effect of dredger fill,which indicates that the solidified effect of P-N(PAM and water glass)double mixed is better than the single doped,and the solidified effect of water glass single doped is better than the PAM single doped.(6)The influencing degree to solidification effect of such factors as the proportion of curing agent and curing age decrease in order as follows: curing age > water glass proportion >PAM proportion;the optimal solidification conditions are 0.3%proportion of PAM and 4% proportion of water glass and 28 days' curing period.(7)Before solidification,the microstructure of dredger fill is loose with developed pores,and the pore size distribution is dominated by super large pores and large pores.After solidification,the pore ratio and porosity decrease,the pore size distribution is converted into most middle pores and small pores as well,while the fractal dimension increases.The longer the curing age,the smaller the pore amount and pore size of solidified dredger fill are,but the larger the fractal dimensions are.(8)The solidification mechanisms of PAM mainly include flocculation,adsorption and shielding effect that contribute to the network structure formed by bridging action between particles,which strengthen the cementation of dredger fill particles.The solidification mechanisms of water glass are the pores filled with silicic acid gel and calcium silicate gel particles produced by chemical reactions between clay minerals and water glass.The solidification mechanisms of P-N(PAM and water glass double mixed to solidify the dredger fill)are that PAM can strengthen the cohesive force between the particles,while the water glass can react with the dredger fill to produce gel and precipitation to fill pores. |
PDF Full Text Request