Early warning of settlement and deformation of high-rise buildings on soft foundations in karst areas
The background of this article pertains to a high-rise building project,which encompasses a building land area of about 4,630 m2 and features a roughly square shape in its plane. The safety classification of the building structure is designated as Level 2,while the foundation design is categorized as Level A. The foundation form is raft foundation. This building project is of high engineering importance. According to the survey results,underlying strata of the building foundation are mainly composed of clay and limestone layers,each possessing distinct engineering properties that are generally unfavorable. In addition,the average annual rainfall in the project area is 1,107.27 mm,and the dissolution effect of the bedrock will continue. Even worse,the building has already undergone unfavorable deformation. Therefore,to ensure the safe operation of the building,it is necessary to conduct research on early warning of its settlement and deformation.In this study,a total of three types of warning criteria were constructed,namely,stability criterion,ultimate deformation criterion,and deformation rate criterion. Among them,the implementation of stability criterion involves sharp point mutation analysis. This technique derived mutation characteristic values from sharp point mutation analysis of building settlement data and used these values to assess the stable state of building settlement. The ultimate deformation criterion was calculated with the use of the ultimate displacement formula to obtain the ultimate deformation value. This value was then combined with existing monitoring data to construct corresponding criterion indicators. The implementation of the deformation rate criterion was conducted with the rescaled range method,which calculated the Hurst index through rescaled range analysis of building settlement data. This analysis evaluated the development trend of building settlement and deformation. Giving the differing emphases of the three criteria,the early warning level of building settlement and deformation,determined based on principle of unfavorable conditions,is deemed reasonable and accurate through comparative analysis.According to the analysis results,there is a significant difference in settlement and deformation among the monitoring points of the building,with a range of 22.76-56.27 mm,indicating notable settlement characteristics. The primary causes of this settlement are the soil and groundwater conditions of foundation. In the process of early warning of building settlement and deformation,the analysis mainly focuses on monitoring points JC3-JC5. The stability criterion shows that the △ values of the three monitoring points are all greater than 0,indicating that they are all in a stable state,and their corresponding early warning levels of settlement and deformation fall into Levels I-III. The range of evaluation indicators for ultimate deformation criterion is from 0.61 to 0.74,corresponding to the early warning Levels Ⅱ-Ⅲ of settlement and deformation,that is,the early warning level of JC5 monitoring point falls into Level Ⅱ,and the other two monitoring points are Level Ⅲ. The deformation rate criterion shows that the Hurst index values of the three monitoring points are all less than 0.5,indicating a decreasing trend in the rate of building settlement and deformation. The trend level of JC3 monitoring point is Level 2,while that of the other two monitoring points is Level 1. By comparison,based on the principle of unfavorable conditions,the early warning level of the three monitoring points is determined to be Level Ⅲ. Therefore,the degree of settlement hazard for this building is moderate. It is necessary to not only increase the monitoring frequency to observe subsequent changes but also to take reinforcement measures.Through this study,a novel approach has been developed for the early warning of building settlement and deformation. This method offers a theoretical basis for ensuring the safe operation of buildings in later stages and holds significant practical implications.
万方数据
维普
