Behaviour of diaphragm walls and settlements from deep excavations in a marine clay

2022 ◽  
Vol 14 (2) ◽  
pp. 868
Author(s):  
Mateusz Frydrych ◽  
Grzegorz Kacprzak ◽  
Paweł Nowak

In this article, the authors consider a completely new approach in design, which is related to the use of previously un-adapted technologies known to bridge engineering in geotechnical issues for prestressing of diaphragm wall during deep excavations execution. The bridge technology described here is the prestressing of concrete structures. Hazards related to deep excavations and methods of digging them, such as the ceiling method and top&down method, are presented. Current problems in supporting deep excavation slopes are related to the use of extensive quantities of materials (such as steel struts, ground anchors, or concrete and reinforcement steel). The authors’ method helps to achieve a higher level of sustainability, which is important in a modern approach to geotechnical engineering. The non-linear arrangements of the cables according to the occurrence of the prestressing moments for a given phase are presented. Results related to numerical analysis—showing the correctness of the method and cost optimization results, showing possible savings are presented. The article is a part of the set. In the second (already published) article titled “Modern Methods of Diaphragm Walls Design”, the authors present the concept of the calculation methodology for diaphragm wall design.


2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Chengyong Cao ◽  
Chenghua Shi ◽  
Linghui Liu ◽  
Jianwen Liu ◽  
Mingfeng Lei ◽  
...  

Dewatering using the dewatering systems composed of diaphragm walls and pumping wells is commonly adopted for deep excavations that are undertaken in deep aquifers. However, dewatering can sometimes induce environmental problems, especially when diaphragm walls cannot effectively cut off the aquifers. This paper mainly presents an innovative excavation technique combining dewatering excavation and underwater excavation without drainage, which is employed for a deep shaft excavation in ultrathick aquifers (up to 60–70 m thick aquifer) in Fuzhou, China. The shaft excavation with the depth of 41.6 m below the ground surface (BGS) is divided into two major phases, that is, (1) the first part of the excavation (the depth of 23.6 m BGS) is conducted by the way of conventional dewatering and braced excavation (Phase I) and (2) the second excavation with the depth of 23.6 m to 41.6 m BGS is carried out by the novel underwater excavation without drainage technique (Phase II). Field monitoring results show that the ratios of maximum ground surface settlement δvm to the excavation depth He in this case ranged from 0.03% to 0.1%. Most of the ratios of maximum lateral wall deflection δhm to excavation depth He are less than 0.1%. All these results are lesser than that predicted by empirical methods, which also confirmed the applicability of this innovative excavation. Thus, this innovative solution can be applicable to other deep excavations that are undertaken in ultrathick aquifers, especially for the excavation of coarse sediments with high permeability.


2001 ◽  
Vol 38 (2) ◽  
pp. 338-348 ◽  
Author(s):  
Teoh Yaw Poh ◽  
Ing Hieng Wong

The basement excavation of the Singapore Post Center involved extensive jet-grouting to improve the soft marine clay present within the excavation. The treated soil mass, with much improved strength and deformation characteristics, was intended to act as an internal strut below the bottom of the excavation level, reducing movements caused by the basement excavation. This paper presents the performance of a well-instrumented field jet-grouting trial during the construction of the building basement. Results of monitoring suggest that the jet-grouting trial caused the retaining diaphragm walls and the adjacent soils immediately behind and at some distance away from the walls to move away from the jet-grouted area. The maximum free field lateral soil movements in the excavation side of the jet-grouted mass were much larger than the corresponding lateral movements behind the wall. The results suggest that the diaphragm wall provided considerable restraint, thereby reducing the lateral movements of the soil behind the wall induced by the jet-grouting. Bending moments were induced in the diaphragm walls due to the jet-grouting work. The jet-grouting also caused some increase in the lateral earth pressure and the piezometric levels.Key words: jet-grouting, ground improvement, diaphragm wall, ground movements.


2000 ◽  
Vol 49 (1) ◽  
pp. 46-49
Author(s):  
Takeo SUZUKI ◽  
Toshimitsu KUNITO ◽  
Motohiro NISHI

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