Failure of circular shaft subjected to hydraulic uplift: Field and numerical investigation

Zhao, Guoqing; Yang, Yiqin; Meng, Suyun

doi:10.1007/s11771-020-4293-2

Cited by 12 publications

(3 citation statements)

References 22 publications

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“…Then, by comparing with numerical and experimental models, Madanayaka and Sivakugan [31] validated the fragment method to estimate the hydraulic exit gradient and the flow for circular cofferdams in AXSflow conditions. Zhao et al [32] conducted both numerical analysis (FEM) and full-scale field tests on shaft construction project located in Guangzhou (China), to examine the circular shaft diameter effects on seepage failure by heaving and to analyse its failure mechanisms, as well as to develop a reasonable method of evaluating the stability of the circular shaft exposed to hydraulic upheave. The authors found that the results obtained from the FEM analysis are in good agreement with the phenomena observed at the site.…”

Section: Figure 2 Prismatic Failure Considering Friction In Axisflow ...mentioning

confidence: 99%

Numerical Analysis of Seepage Failure Modes of Sandy Soils within a Cylindrical Cofferdam

2022

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Soil seepage failure within cofferdams is a dangerous phenomenon that always poses difficulties for designers and builders of excavations in zones with high water levels. When the hydraulic head difference H between the upstream and downstream sides reaches a critical height, the downstream soil seepage failure occurs. Depending on soil properties, soil-wall interface characteristics, and cofferdam design, different seepage failure modes can be observed: heaving, boiling, liquefaction, or failure by reduction of the passive earth pressure. In the literature, there are differences, sometimes very large, in the critical value of the hydraulic head loss Hc/D inducing seepage failure given by several methods proposed for stability verification. Then, complex cases are generally approached using simplifying assumptions and adopting large safety factors to take account of uncertainties. In practice, geotechnical engineers deal with many kinds of excavations and different shapes of cofferdams, such as rectangular, square, or circular, which generate three-dimensional (3D) flow conditions. Axisymmetric seepage flow through the soil in a circular cofferdam is often used to model such 3D seepage flow. In this paper, using the numerical code FLAC, several numerical simulations are carried out in axisymmetric groundwater flow conditions to analyze the seepage failure modes of cohesionless sandy soils within a cylindrical cofferdam. The effects of the cofferdam radius, internal soil friction, soil dilatancy, and interface friction on the Hc/D value and failure mode are studied. The numerically obtained seepage failure modes are presented and discussed in various scenarios. The present results, illustrated in both tables and graphs, show a significant decrease in the value of Hc/Dinducing seepage failure, with a decrease in the cofferdam radius. They also indicate the sensitivity of the seepage failure mode to internal soil friction, soil dilatancy, interface friction, and cofferdam radius. As well, new terms are proposed for the seepage failure mode designations based on the 3D view of the downstream soil deformation. Doi: 10.28991/CEJ-2022-08-07-06 Full Text: PDF

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Section: Figure 2 Prismatic Failure Considering Friction In Axisflow ...mentioning

confidence: 99%

Numerical Analysis of Seepage Failure Modes of Sandy Soils within a Cylindrical Cofferdam

2022

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“…Based on the experimental results of Yousefi et al (2016) [18], where they simulated the seepage flow and its behaviour downstream of a sheet pile under inclined and vertical configurations using laboratory models to study the boiling phenomenon, an inclined configuration with an angle of 60° to the horizontal direction and a ratio of sheet pile depths d/D=0.34 and d/D=0.44, in which d is the vertical penetration depth of the sheet pile and D is the thickness of the foundation material for inclined and vertical configurations respectively, have successfully reduced the boiling phenomenon and exit vertical hydraulic gradient. Zhao et al (2020) [19] conducted both an FEM and full-scale in-situ tests in Guangzhou, China, to study the effects of circular shaft diameters on failure by uplift and to analyse its failure mechanisms, as well as to determine a reasonable stability judgement method for circular shafts subjected to hydraulic uplift. The authors found that the observed phenomena on-site have good agreement with the results obtained from the finite element analysis.…”

Section: Figure 1 the Development Of Piping Around Waterfront Structmentioning

confidence: 99%

FEM Optimisation of Seepage Control System Used for Base Stability of Excavation

Ouzaid¹,

Benmebarek²,

Benmebarek³

2020

Civ Eng J

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With the existence of a high groundwater level, the head difference between the inside and outside of an excavation may lead to the loss of stability of the excavation’s surface. Hence, a fundamental understanding of this occurrence is important for the design and construction of water-retaining structures. In some cases, the failure mechanism cannot be predicted exactly because of its mechanical complexity as well as a major lack of protection systems and not adopting effective countermeasures against this phenomenon. The article took a tranche from an 80 km long open sewer located in the Ruhr area, Germany as an example to establish a hydro-geological model and analyse the instability of the excavation base surface caused by the groundwater flow at 45m deep and to present the effectivity of an adopted drainage system inside the excavation pit as 39 columns of sand to relax the pore water pressure. By using the Finite Element Method (FEM) analysis, the failure mechanism was investigated before applying any countermeasures, and the total length of the adopted countermeasure system was minimised. Also, various position tests were performed on the adopted drainage system to confirm the optimised position. The results of this numerical study allowed the deduction of the importance of the used drainage system by achieving 44% more in the excavating process. After achieving the required excavation depth, a further increase of the sand columns’ penetration may be considered non-economic because, after adding extra depth, all the situations have the same safety factor. In addition, this can provide a reference for the optimised position of the sand columns where they must be applied right by the wall and limited by a critical distance, D/2, half of the embedded depth of the wall.

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“…However, these foundation pits are often built next to riverbanks, which pose challenges for designing and safely constructing these structures. Accordingly, the design and construction of circular foundation pits have attracted the attention of many engineers and researchers [1][2][3][4]. For example, Faheem et al [5] used the fnite element method to study the stability of rectangular foundation pits.…”

Section: Introductionmentioning

confidence: 99%

Research on the Stress and Deformation Characteristics of Circular Foundation Pit during Excavation in Sand Soil

Gao

Tian

et al. 2023

Advances in Materials Science and Engineering

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The stress and deformation response characteristics of the support structure in the process of excavation and support of circular sand foundation pit are complex. The existing research results lack a general analysis method for the mutual check between the field monitoring data and the numerical simulation results. This research relies on the excavation and support project of a circular foundation pit in the sandy soil layer of the west anchorage of Humen Second Bridge. The force and deformation characteristics of foundation pit soil are monitored and structure is supported during construction. A new method for checking simulation parameters based on the excursion monitoring data of the diaphragm wall is proposed. The modeling and calculation theory of foundation pit excavation and support process is established. The superposition calculation of pore water pressure is used to realize the foundation pit seepage-stress coupling. The effects of steady-state seepage conditions on the equivalent strain of foundation pit soil, the displacement of the diaphragm wall, and the axial force of the lining are compared and analyzed. The stress and deformation mechanism of the soil layer and supporting structure during the excavation and support of a circular foundation pit in the sand layer is obtained.

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Failure of circular shaft subjected to hydraulic uplift: Field and numerical investigation

Cited by 12 publications

References 22 publications

Numerical Analysis of Seepage Failure Modes of Sandy Soils within a Cylindrical Cofferdam

Numerical Analysis of Seepage Failure Modes of Sandy Soils within a Cylindrical Cofferdam

FEM Optimisation of Seepage Control System Used for Base Stability of Excavation

Research on the Stress and Deformation Characteristics of Circular Foundation Pit during Excavation in Sand Soil

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