Research On Reinforcement Method Of Loess Foundation Under Existing Building

Because of the complexity of the loess foundation and the limitation of design,construction and knowledge level,Large settlement or uneven settlement of loess foundation under existing building arose frequently,It needs to be strengthened to ensure that the building is used properly and safely.In this paper,based on practical engineering,the peculiarities of three reinforcement methods of high pressure jet grouting pile,pit-jacked pile and manual hole digging pile are studied.through indoor and in-situ engineering tests,deformation monitoring and other methods.The main work and conclusions are as follows:(1)Through the calculation and analysis,When it is necessary to consider the negative friction of the thick soil layer,The strength of the high-pressure jet grouting pile is more difficult to meet the requirements;The pit-jacked pile construction is more difficult when pile length is larger to achieve higher single pile bearing capacity.(2)The relationship between pile strength and single pile bearing capacity is obtained by test of soil strength test and static load test of single pile bearing capacity.Deformation monitoring results show that the jet grouting pile is used for existing building foundation reinforcement,can effectively control the ground settlement,and in the reasonable arrangement of construction sequence and construction speed,the additional settlement caused by jet grouting pile construction of raft foundation is small,However,it will cause a large additional settlement to the independent foundation.(3)The pile-sinking resistance of pit-jacked pile is analyzed and studied.It indicates that the pile-sinking resistance is different from the ultimate bearing capacity of the single pile,and the relationship between them is related to the actual soil layer property.For low intensity loess,the side friction of pile in the process of pile-sinking is less than that in the normal working condition,and the ratio is about 0.4~0.6.The critical buckling load of static pile is studied by theoretical analysis.(4)The manual hole digging pile has the advantages of large bearing capacity and reliable construction quality.When the thickness of the filling or collapsible loess is relatively large,it is obviously advantageous to use the artificial digging pile for foundation reinforcement.