Research On Monitoring Technology Of Deep Foundation Pits In Collapsible Loess Regions And Its Applications

With the rapid progress of infrastructure in china, more and more construction projectsare carried cut in loess regions. The collapsible property of loess than becomes a hot issue inconstruction engineering. Loess looks stable, but its engineering property changesdramatically after immersion and it even loses original strength. Major factor of engineeringaccidents caused by collapsibility lies in the unsteady support of foundation pits. Thusdeformation monitoring of foundation pits appears to be more and more important.The current “Technical code for monitoring of build founding foundation pitengineering” indicates it is not applicable for collapsible loess regions. In addition, neither“Code for building construction in collapsible loess regions” nor “Technical specifications forsafe retaining and protection of building foundation excavation engineering in collapsibleloess regions” clearly defines monitoring items, frequency or early warning values.Difficult operation in the actual project.Based on specific engineering projects this paper analyzes the current research oncollapsible loess and deformations monitoring of foundation pits. Major contributionsinclude:1. The loess distributions, cause, micro structure, collapsibility mechanics andengineering properties are analyzed.2. Type and feature of support structures for foundation pits in collapsible loess regions,the scopes of their applications, and various monitoring items are introduced.3. Typical measurement methods of foundation pits are expounded. Based on Technicalspecifications, methods are explored to figure out early warning values and monitoringfrequency for foundations pits in collapsibility loess regions.4. According to monitoring data obtained in a foundation pit in Xi`an, a typicalcollapsible loess region, the deformation of support structure is analyzed, and the validity ofthe monitoring frequency and early warning values suggested in this paper are testified.In summary, this paper focuses on the key issues of foundation pit monitoring incollapsible loess regions, and proposes methods of figuring out monitoring frequency andearly warning values for such regions. It is of theoretical and realistic significance to improvethe efficiency of foundation pit monitoring and economic benefits.