Feasibility Study On Foundation Pit Supporting By Locking With Reinforced Concrete Cast-in-situ Pile And Cement Treated Column

In this thesis, introduces the feasibility study on a new supporting system with reinforces concrete cast-in situ pile and cement-soil secant retaining wall through laboratory experiment and project inspection. It also carries on four levels of single-factor laboratory experiments with three sample soils: clay, cohesionless soil and sandy soil, concerning three elements: cement mixture ratio, age, water content in order to find out the contractibility under different test conditions, and also the permeability of locking surface between cement soil and concrete. Based on similarity theory and model method and cement-soil beam bending test, the comparative bending of cement-soil beam crackability limit is obtained, and finally takes the project inspection on soil pressure, pore water pressure and deep soil horizontal displacement at the testing section. According to cement-soil contractibility experiment, it can be observed that 1.under natural test condition the cement-clay soil's contractibility increases in accordance with the age growth, decreases in accordance with the rise of water content as well as cement mixture ratio, and the contractibility can be effectively decreased by controlling cement mixture ratio at over 15%,2.under natural test condition cohesionless soil expands in the first 14 days and contracts later, the more cement mixture contents or water content, the less it contracts, and the contractibility can be effectively decreased by controlling cement mixture ratio at 20%-25%, expansion rate increases mixed with expander and with age growth, 3.under standard condition cohesionless soil expands in first 14 days and contracts later, the cement mixture ratio should be 15%-20% according to different water-containing soil to improve the cement soil expansion. 4.under standard test condition sandy soil expands in the first 14 days and contracts later, it expands with rise in cement mixture ratio and water content, mixing expander helps expansion but just in the early stage,. Experiments tell the anti-permeability of locking surface between cement soil and concrete reaches 0.18-0.24 Mpa, meeting theoretical demands. By analysis on the inspection data the thesis concludes the requirements and techniques on foundation pit supporting by locking with reinforced concrete cast-in-situ pile and cement treated column. The method was proved feasible and should be spread in practice.