Research On The Influence Of The Change Of Foundation Stiffness On The Uneven Settlement Of A High-rise Residential Building

High-rise residential is the most important business type in real estate development,which has developed features of large volume and short construction period.In the construction of different Chinese cities,the uneven settlement of foundations often occurs in the construction of high-rise residential projects due to the complex geological conditions.The damage caused by the uneven settlement of foundation is slow and continuous,which can lead to structural safety accidents,such as continuously cracking and tilting of high-rise residential buildings.The above-mentioned problems have seriously affected the construction progress,as well as the normal operation of the houseowners.However,compared with engineering experience,there are few studies on the uneven settlement of high-rise residential buildings.Accordingly,this study cond ucts an application analysis on the influence of foundation stiffness change on uneven settlement based on a uneven settlement accident of a high-rise residential building.The main ideas and contents of this study are as follows:(1)According to the existing research and engineering experience,the hazards of uneven foundation settlement are listed and three causes of uneven foundation settlement are analyzed.Additionally,the common reinforcement measures for pile foundations and their shortcomings are described.(2)Taking a high-rise residential building as an example,the modeling of the shear wall structure-pile-raft foundation-foundation interaction system is introduced in detail,which includes the establishment and verification of the upper shear wall model,the comparison and selection of raft elements,the comparison and selection of the foundation soil constitutive model,and the setting of the contact between the pile and the soil.(3)Based on the interaction model between shear wall structure,pile-raft foundation,and foundation,the influence of foundation stiffness adjustment on the uneven settlement of high-rise residential buildings is analyzed.By changing the thickness of the raft,the elastic modulus of the foundation soil,and the reinforcement depth of the surface foundation soil,the deformation and stress distribution of the interaction model are studied.Results show that the increase of the raft thickness is beneficial to adjust the uneven settlement of the foundation under the simulated uneven settlement condition.For the analyzed high-rise residential building,the optimal thickness of the raft is about 1.6 m.Meanwhile,the increase of the elastic modulus of the foundation soil helps to adjust the uneven settlement of the foun dation.When the elastic modulus is less than 100 MPa,the adjustment has the best effect.On the contact,the increment has little effect on the uneven settlement of the foundation when the elastic modulus is greater than 100 MPa.In addition,when the reinforcement depth of the surface foundation soil is less than 10 m,the adjustment of the uneven settlement has the best effect.When it exceeds10 m,the adjustment has no significant effect.Therefore,for high-rise residential buildings,the optimal reinforcement depth of the foundation soil under the raft is 10 m.(4)An example of the uneven settlement of a high-rise residential building is introduced.Combined with the previous settlement monitoring and the superstructure investigation results,the ca use of the accident is analyzed.Taking "increasing the stiffness of the foundation" as the idea of the reinforcement,the original pile foundation is converted into a pile-raft foundation,based on which the high-rise residential building is reinforced.The monitoring data after the reinforcement shows that the reinforcement has a significant effect.The idea of the reinforcement in this study can provide a reference for similar reinforcement projects.