Optimization Research For Stabilizing The Fluvial-lacustrine Soft Soil In Hefei Using Central Composite Design Of Response Surface Methodology

A large of fluvial-lacustrine soft soil is in Binhu New District of Hefei,which is unfit for the urban construction,for its high water content,low bearing capacity and large settlement deformation,and thus the soft soil foundation must be stabilized for project construction.The design theory and application in practical engineering research of composite curing agent for stabilizing the fluvial-lacustrine soft soil were carried out using central composite design of response surface methodology through a combination of experimental research and theoretical analysis.In view of the wide range of applications of cement in the field of soft soil stabilization,cement was selected as the main curing agent,GGBS,gypsum and calcium oxide as external additives to improve fluvial-lacustrine soft soil stabilization.Under the condition of the cement content is 15% and the water-cement ratio is 0.5,the optimizing mixture ratio of composite curing agent were obtained from CCD method,by which the function relationship can be not only established between the influence factor and the target value,but also the interaction law can be analyzed between different factors,with the contents of GGBS,gypsum and calcium oxide as affecting factors,with the unconfined compressive strength values of stabilized soils as response values.It shows that the mutual-influence for GGBS and gypsum is significant and the strength value response to the variation of GGBS content increases first and then decreases with the increase of gypsum content.By mutual-influence analysis,it is found that the optimal ratios of three kinds of curing materials are9.78%(GGBS),4.8%(gypsum),3%(calcium oxide)respectively and under the condition of optimal ratios,the strength of stabilized soil can reach 923.358 k Pa(7 d).The strength model of stabilized soil was established considering the influence of various factors based on the central composite design of response surface methodology.The results show that the interaction between organic matter content and water content,dosage of curing agent and water content have a significant effect on the strength of stabilized soil.Through the analysis of the influence of single factor on the strength,the content change of composite curing agent has the greatest influence on the strength,and when the content of the curing agent was less than 15%,the strength of the stabilized soil was enhanced with the increase of the dosage of curing agent,while the dosage of curing agent was more than 15%,the curing agent did not play a positive role in the strength increasing of stabilized soil.The interaction analysis between initial organic matter content and water contentshows that when the dosage of curing agent is fixed at 14%,the strength of the stabilized soil has the variation tendency of gradually decreasing with the increasing of organic matter content when the water content changing within the scope of the study,and the decreasing tendency of the stabilized soil strength was gradually not significant with the further increasing of water content corresponding to the different organic matter content.The interaction analysis between initial water content and the dosage of curing agent shows that the strength of stabilized soil has the variation tendency of firstly increasing and then decreasing with the increasing of the dosage of curing agent when the organic matter content is fixed at 7.5%,with the water content changing within the scope of the study,and when the strength of the stabilized soil reaches the maximum value,the corresponding dosage of curing agent decreases with the increasing of water content at this point.The results show that there is a negative correlation between the dosage of curing agent and the water content when the optimal value of unconfined compressive strength of 28 days reached.