Study On Strength Optimization Of Cement-soil Mixing Piles In Coastal Beach Area Of Huanghua

Because of the construction needs of a project in Huanghua port,the cement-soil mixing pile method was used to stabilize the foundation in the field,but the ordinary Portland cement and anti-sulfate cement can not play a very good stabilizing effect on saline soil.It is necessary to optimize the mix ratio and strength of cement-soil mixing pile.Firstly,the preliminary indoor experiments was designed,It is clear that water content,types of stabilizer and slag content are the main influencing factors.Secondly,in view of the above factors,the effects of water content of saline soil,types of stabilizer and cement-fine slag ratio on the strength of stabilized soil were studied by selecting different factor levels.Finally,a variety of experimental methods were used to test the characteristics of stabilized soil:the fracture characteristics and micro-morphology characteristics of stabilized soil were observed,the unconfined compressive strength,the content of hardened materials and the loss on ignition of stabilized soil were tested;the types and contents of hydration products of stabilizer were tested.The strength formation mechanism of stabilized soil is studied from the point of view of the role of water and mineral admixtures in stabilized soil.The results show that:1)The formation of the strength of the stabilized soil is affected by water in two aspects.On the one hand,more hydration products will be produced to improve the strength of stabilized soil;on the other hand,the internal voids will be larger and the strength will be reduced.2)Portland cement stabilizer with 75%slag has the best stabilizing effect.The strength can reach 8 MPa at 28 days and 12 MPa at 90days.The stabilizing effect is better than that of sulfate-resistant cement,ordinary Portland cement and fly ash.3)Cl^-in saline soil is combined with hydration products of stabilizer and forms 3CaO·Al₂O₃·CaCl₂·10H₂O.However,it is not the main reason for the difference of strength of stabilized soil.Compared with the burning loss index,there is a more obvious correlation between the hardened materials content index and the unconfined compressive strength of the stabilized soil.4)The hardened materials formed in the stabilized soil is the main source of the strength of the stabilized soil.The hardened materials is composed of the hydration products of the stabilizer and the soil particles bonded with it.The formation of the consolidation is affected by amount of the hydration products and the aggregation of the stabilizer.The increase of the content of the consolidation improves the strength of the consolidated soil.5)The main reason for granulation is that slag rich in Al produces Al³⁺during hydration,and its ion exchange capacity is much higher than that of Ca²⁺produced by cement hydration.Through ion exchange,the diffusion layer in the double electric layer of soil particles becomes thinner.Particles condense due to the decrease of spacing.The stabilizer of cement-soil mixing pile was optimized in this paper,and the strength of stabilized soil was improved by mixing mineral admixture.The new stabilizer widens the application scope of cement-soil mixing pile,reduces the construction cost,and provides a certain reference for the choice of stabilizer for similar projects.