General Report - Session 3

This General Report summarizes the 84 papers accepted for the Session 3 focused on: - 3a. Case Histories on Failure and Remediation of Slopes, Dams, Embankments and Landfills (53 papers), - 3b. Case Histories on Failure and Remediation of Retaining Structures, Slurry Walls, and Deep Excavations, Dewatering, Stability (27 papers), - 3c. Improving the Stability and Maintenance of Monuments (4 papers). The papers originate from 26 countries (11 European countries, 3 American countries, 11 Asian countries and 1 African country). The papers cover a number of relevant topics divided into three different sub - sessions. As for the two papers included in Session 3c, only one deals with maintenance and retrofit of historical monuments. Indeed paper 3.03c is more pertinent to session 3b. On the other hand some papers included in Session 3a could also be considered in Session 3b and vice versa

DYNAMIC CONSTRUCTION CONTROL METHOD FOR A DEEP FOUNDATION PIT WITH SAND-PEBBLE GEOLOGY

Taking the water-rich sand and pebble geology deep foundation pit of Jinfu Station of Chengdu Metro Line 6 as the research object, combined with the ladder excavation method of slotting, utilizing finite difference software FLAC 3D as well as on-site monitoring result, the deformation law of the diaphragm wall during the dynamic excavation of the foundation pit is analysed, and the influence of the relative stiffness between the vertical and horizontal walls of the foundation pit on the lateral deformation of the retaining structure is discussed. The results show that while using the ladder excavation method of slotting, the maximum lateral displacement of the underground diaphragm walls decreases gradually with the excavation depth of the foundation pit, which occurs at the intersection of the middle point of the oblique excavation line and the step distance section of the transverse excavation. Additionally, the lateral displacement increases closer to the excavation section. The lateral displacement of the envelope enclosure mainly depends on the relative constraint stiffness of the vertical and horizontal underground diaphragm wall of the foundation pit. The use of the ladder layered excavation method of slotting can effectively reduce the lateral displacement of the underground diaphragm wall. The simulated result and on-site monitoring result are nearly the same. These results can provide a corresponding theory and engineering basis for the selection of excavation methods for the same type of sand and pebble stratum foundation pit

Deformation rule of bored pile & steel support for deep foundation pit in sandy pebble geology

Regarding the whole excavation process of the support system of the Southwest Jiaotong University Station of Chengdu Metro Line 6 (the deep foundation pit bored pile + steel support and support system) as the engineering background, this paper studies the deformation rule of the deep foundation pit bored pile + steel support of the sandy pebble foundation. The deformation rule of this support system, the settlement rule of the ground surface outside the pit, and the rule of the uplift of the loose at the bottom of the pit are studied. A key analysis of the positive corner of the foundation pit is conducted, and the rationality of the optimization of the support scheme is evaluated. This paper provides effective guidance for the subsequent deep foundation pit construction and provides a reference for deep foundation pit construction

Deformation Law and Spatial Effect of Deep Foundation Pits for Subway Construction in Soil-Rock Composite Strata in Seasonally Frozen Areas

The stability and safety of metro deep foundation pit in the soil-rock composite stratum in the seasonally frozen area are the key issues in the design and construction of the foundation pit. In order to ensure the soil-rock composite stratum in the seasonally frozen area, the deformation of the supporting structure is within the safe range when the deep foundation pit is excavated. At the same time, it will reduce the impact of the construction of metro deep foundation pit on the surrounding buildings. During the construction of foundation pit, close monitoring shall be carried out and the actual monitoring data shall be studied and analyzed. During the excavation of each layer of the foundation pit, monitor the displacement change of the foundation pit support structure and the settlement change of the surrounding ground surface, study the deformation law of the subway deep foundation pit in the soil-rock composite layer, and discuss the spatial effect of the foundation pit excavation in the seasonally frozen area. This paper mainly takes the deep foundation pit project of Anxin Road Station of Changchun Metro Line 5 as the research object, and analyzes the actual monitoring results. The results show that: (1) With the long side of the foundation pit, the deformation of the retaining structure of the foundation pit increases with the distance from the pit corner, and the middle of the long side of the foundation pit is less constrained by the retaining structure. (2) During the excavation of soil-rock composite foundation pit in seasonally frozen soil area, the pile displacement, axial force of support and uplift of support structure caused by rock excavation are relatively small, while the lateral displacement of foundation pit below the rock surface and thawing settlement deformation of soil are basically unchanged. The maximum lateral displacement of the foundation pit at the upper part of the rock surface moves upward. During the construction of deep foundation pit, there is a large displacement before the erection of the third layer of steel support. Attention should be paid to the soil properties of the deep silty clay layer, as well as to the rapid construction and synchronous maintenance