Geogrid-reinforced structures are extensively adopted in various engineering fields. At present, the influence of boundary conditions was not considered in design methods, bringing hidden dangers to the safety of the structure. In the current study, a series of pullout tests were carried out on high-density polyethylene (HDPE) geogrid-reinforced coarse sand. The magnitude and growth pattern of pullout resistance and the variation laws of interfacial shear strength indexes under four types of boundary conditions were analyzed. Additionally, the boundary reduction coefficient (BRC) was introduced to establish the relationship between rigid and flexible boundary for the design of the structure. The tests results showed that the boundary conditions cannot be ignored in the design of structures, especially in the front. When the normal loading was up to 120 kPa, the BRC-top and BRC-positive could be taken as 0.9 and 0.5, respectively, and verified by fitting results. The boundary conditions affected the pullout resistance, while the vertical loading corresponding to the maximum pullout resistance was not related to boundary conditions. Investigating the interaction of the geogrid–soil under different boundary conditions can help to improve the understanding of the behavior of reinforced soil structure, and to achieve a more efficient and economical design.

Effect of Boundary Conditions on the Mechanical Behavior of the Geogrid–Soil Interface

Research on the plume stability of air bubble curtains under low transverse flow velocity environment in dredging engineering

This paper investigates the failure mechanism of nonuniform large geotextile-reinforced cofferdam under seepage and excavation effects on soft sediments. A numerical model is established and validated with available testing results. Then, parametric studies are carried out to investigate the potential influence factors. This study found that the difference between the upstream and downstream water levels and the excavation depth both have significant influences on the stability of cofferdams, where excavation is the key influence factor affecting the stability of the cofferdam. Numerical results revealed that the safety factor could reduce by about 20% with excavation of about 1.5 m. An empirical equation is proposed for quantitative prediction of the stability of geotextile-reinforced cofferdams. A thorough understanding about the failure mechanisms of cofferdams as well as an empirical formula for predicting the stability is concluded in this study, which could provide engineering guide for flexible foundations reinforced by geotextiles. 

Stability of Nonuniform Large Geotextile-Reinforced Cofferdam under Seepage and Excavation Effects

This paper analyses the deformation and force behavior of a wood-piled island cofferdam based on the principle of equivalent bending stiffness. The horizontal deformation and bending moments in wood piles and the axial stress in tension bars on top of piles were both analyzed by the finite difference (FD) method. Except for the analysis of the cofferdam construction process, the influence of the pile length, the dam width, the tension bar interval, and the pile interval, among the commonly adopted parameters, were detailly examined in numerical simulations. In addition, a reinforced wood-piled cofferdam model by steel pipe piles has been established to quantify the effect of reinforcement. It was found that the dewatering inside the cofferdam was detrimental to cofferdam stability. The pile deformation reached maxima (roughly 0.6% of the pile length) at solidifying stage after dewatering. The changing trend of the cofferdam structure force within a safe district was consistent with the displacement. The dam width had a vital effect on the stability of the cofferdam, especially on the horizontal deformation. The steel pipe pile reinforcement scheme performed better in further deformation control, providing a new idea for island-type cofferdams with rigorous structural deformation control.

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Deformation and Force Analysis of Wood-Piled Island Cofferdam Based on Equivalent Bending Stiffness Principle

Earth and rock-filled gabions have valuable applications in engineered dams, walls, and foundations, as well as for erosion control and military force protection. A gabion mattress, also commonly known as a marine mattress, is a variation of the gabion that utilizes geosynthetic materials with a relatively small height compared to its much larger length and width dimensions. While gabion baskets and walls are typically used for slope stability, marine mattresses are primarily used to protect against erosion and wave action along slopes. While uplift stability and down-slope sliding are two concerns to be mitigated when incorporating a marine mattress into designs, the presence of a marine mattress on a slope affects the underlying slope’s stability. Slope stability analyses are essential for design of sloped applications of marine mattresses, particularly on soft soils, and the ability to accurately set up analysis software to aid in geotechnical design is crucial in making sound engineering recommendations. While there is some information in the literature regarding slope stability regarding gabion boxes baskets and walls, as well as geosynthetics and revetment stone layers along slopes, there is limited information on modelling revetment stone filled geosynthetic gabion mattresses along a slope. In their recent 2021 software update, the limit equilibrium software used in performing the analysis introduced a reinforcement library to choose specific manufactured geosynthetic products. This consists of a limited selection of products from two manufacturers. While geogrids are not included, a marine mattress was not included in the updated version. In this study, the stability of a partially submerged marine mattress was analyzed in five potential ways including modelling as (1) a high-strength material, (2) an unreinforced layer of revetment stone, (3) a layer of revetment stone enveloped by a geosynthetic material, (4) a layer of revetment stone enveloped by a specific manufactured geo-grid, and (5) a surcharge load with the same unit weight as the revetment stone layer. The advantages and disadvantages of each modeling scenario are discussed, and factors of safety for global failure are compared. 

Analyzing Different Methods to Model a Marine Mattress on a Partially Submerged Slope

This paper proposes a new arrangement of geotextile reinforcement stiffness for large geotextile mat cofferdams that often suffer from the failure of the bottom layer mat. Cofferdams using...

Xiaoliang Wang

Papers

Behavior of Large Geotextile Mat Cofferdam with a New Arrangement of Geotextile Reinforcement Stiffness Lying on Soft Sediments