Study On Reinforcement Treatment And Mechanism Of Soft Foundation Engineering Of A Substation In Pearl River Delta Region

The soft soil in the coastal plain area of the Pearl River Delta has the characteristics of strong compressibility,high water content and low shear strength,which leads to low bearing capacity of foundation and often can not meet the requirements of upper load.Groundwater in this area contains organic matter and has certain corrosiveness,which often leads to the problems of low strength,slow solidification and core shape of cement-soil mixing piles.In this paper,starting from the following aspects,on the one hand,to improve the mechanical properties of the lifting mixing pile;on the other hand,through field tests to explore the soft foundation reinforcement treatment methods,in order to enhance the bearing capacity of the foundation,so as to meet the load requirements of the upper buildings(structures)on the foundation.Based on the soft foundation treatment project of a substation in Zhongshan City,Guangdong Province,the consolidation and treatment of soft soil in the Pearl River Delta region are studied.The effect of drainage plate combined with surcharge preloading and cement mixing pile on soft soil foundation treatment is studied and analyzed,and the suitability of geotechnical solidifying agent for soft soil foundation in this area is also explored.Through laboratory tests,the solidification effect of several solidifying agents and their combination on soft soil in this area is explored.Based on the compressive strength,the reinforcement effect is analyzed,and the optimum mixing ratio and reinforcement technology are selected.The influence of different working conditions on cement-soil is simulated by laboratory test,and the treatment effect of drainage plate combined with surcharge preloading and cement mixing pile on soft soil foundation is studied by field test.The test results show that the activator-geopolymer has better solidification effect on cement-soil;different working conditions have certain influence on the strength of cement-soil;groundwater has relatively greater attenuation effect on cement-soil mainly mixed with sodium silicate solidification,compared with geopolymer cement-soil,the suitability of geopolymer cement-soil is stronger;through the micro-structure test,it is found that the solidified soil is mainly through the formation of a new solidified material.The complex reaction between(hydrated calcium silicate)and soil particles makes the solidified material connect the soil particles,filling the pore between the soil particles,forming a three-dimensional network structure,and improving the strength of cement soil.In the field test,through monitoring the settlement,pore water pressure,groundwater level,deep horizontal displacement and other items,it is found that "pile first" technology is applied to soft foundation.The consolidation effect is relatively good,the settlement and the radius of influence on the boundary and the outside are relatively large;"Pile before pile" is not as good as the former in improving the degree of consolidation of soil,but the settlement tends to be stable first under the same heap load conditions,and the influence on the boundary and the outside is relatively small,at the same time,the construction period can be saved to a certain extent;the combined solidifying agent(activator + geopolymer)has a better effect.The solidification effect is consistent with the indoor test in the field core-pulling test,which can improve the mechanical properties of piles and the bearing capacity of foundation.