Papers by Keyword: Hydro-Mechanical Coupling

Abstract: Rammed earth structures are very sensitive to hydric conditions. Experimental studies have been undertaken to understand the link between liquid water transfer and mechanical behavior at structural scale. This study was done on a prismatic rammed earth sample of 15cm x 15cm x 45cm, structured as a wall element with several layers. Samples were subjected to one dimensional drying in an indoor environment. Humidity and temperature sensors were placed on each layer inside the sample. The kinetic of drying was monitored by continuous weighing the sample and humidity measurement at a regular interval. Results of water content evolution suggest that samples dry in two stages; the first stage is associated with relatively high evaporation flux of 13.88 g m^-2h^-1 while the second stage has very low flux of moisture evaporation. Unconfined compressive strength was performed in drying samples after 0, 2, 6 and 8 weeks of drying. In parallel, digital image correlation was used to determine the stiffness of samples. Results show an increase in compressive strength by the rate of 98 kPa per week in the first two weeks, then this rate reduces to 23 KPa per weeks after 8 weeks. These experimental results will allow to enhance the 3D hydro mechanical numerical model developed in the laboratory.

Abstract: Seepage is one of the major influence factors for engineering stability. In this study, the equations of hydro-mechanical coupling in dual-porosity media including the governing equations of deformation and seepage are employed. The fluid gravity in whole system is considered in the seepage governing equation. The solid displacement, pore fluid pressure and fissure fluid pressure are the unknown qualities. The finite element formulation of the governing equations are acquired after using the Galerkin discretization technique. The physical parameters are discussed here. Finally, the state equation method is applied to solve the finite element equations.

Abstract: Deformation of subgrade caused by variation of groundwater level is a problem of hydromechanical coupling. The coupling mechanism of seepage and deformation of subgrade was analyzed, and a model of hydromechanical coupling was then established. The resilient modulus of the model is related to the water content and compactness of subgrade soil. The relationship between them was obtained based on laboratory tests, and was employed to research the influence of rise of groundwater level on resilient modulus and deformation of subgrade. The results showed that the rise of water level had great influence on resilient modulus of subgrade, and the deformation of subgrade can’t be neglected.

Abstract: The causes of water inflow and sand bursting on starting shaft disaster in shield tunnel were analyzed. The analytical model that groundwater seepage from substratum of the reinforced soil to gap in shaft wall on starting shaft in shield tunnelling was established. Using the semi-confined aquifer seepage theory, a practical calculation example was given. The result shows: under the assumption that the reinforced soil was complete exclusion of water, the accidents of water inflow and sand bursting in portal part were influenced by many factors including the length of reinforced soil, groundwater level and so on. The cost and safety of starting shaft engineering had positive correlation with the length of reinforced soil. Lowering the groundwater can significantly reduce water inflow disaster. Comprehensively considered factors of safety, economy, construction period and so on, the reasonable construction parameters can be determined.

Abstract: The mechanical and hydraulic behavior of clay in the excavation damaged zone (EDZ) around underground repository is relevant for the assessment of the safety of geotechnical barriers. By integrating Mohr-Coulomb criterion and damage mechanics considerations, an elasto-plastic damage model is established for clay stone. Based on laboratory and in site investigations, the hydro-mechanical coupled damage model and permeability healing model is developed by the fully coupled hydro-mechanical coupled model, which can predict permeability changes and fractures self-healing in EDZ. Considering the construction of connecting gallery of radioactive waste disposal in deep clay formation in Belgium, a finite element damage model for simulating shield tunneling is proposed. The variations of damage and permeability around the tunnel with time are analyzed in detail. The proposed model is able to effectively depict the main features of hydro-mechanical behaviors of Boom clay.

Abstract: This paper presents a damage model dedicated to unsaturated brittle rocks. It mixes phenomenological and micro-mechanical concepts, and is formulated based on the use of independent state variables (net stress and suction). The expression of the liquid permeability is modified in order to represent the influence of fracturing on interstitial fluid flows.

Abstract: Three-dimensional hydro-mechanical coupling analyses have been conducted on the water-tight structure of the cofferdam for both intake and outlet of Taian pumped storage power station, located in Shandong Province of China. In addition, the effects of excavation on the cofferdam and foundation slopes were also studied by using the 3D FLAC. The calculation results show that the central core of high-pressure grouting has a prefect anti-seepage effect and therefore is able to strengthen the stability of the cofferdam and foundation slopes. The excavation process has only some local effects on the cofferdam and does not greatly affect the global stability of the cofferdam. Therefore, no failure takes place around slope toes. The results show that the width of platform left on the excavation side is reasonable.