In order to evaluate the shear strength and dilatancy behavior of coarse granular soils reinforced with geogrid a large direct shear apparatus (1000×1000×940 mm) was built. A series of shear tests were carried out to study the effect of geogrid orientation and soil volume changes on shear strength. A numerical model is proposed to calculate the shear strength increase. This is verified by the experimental results. Tensile strains in the geogrid can also be calculated using this model.
In order to overcome the limitations of the current standard small direct shear box in testing the shear strength of coarse granular backfill materials, a large direct shear apparatus (1000 by 1000 by 940 mm) was constructed at Carleton University and a series of direct shear tests were conducted with coarse granular soils. In addition, several direct shear tests on soils reinforced with geogrids were also conducted, and the shear strength parameters of the composites were compared with those of natural soils. It is shown that the controlled large direct shear test, though time consuming, provided a useful way of evaluating the behavior of the natural granular soils and reinforced soils.
Properly simulating multiphase flow involving non‐isothermal processes in unsaturated soils requires the development of water retention curve (WRC) models with temperature effects. However, the majority of the existing WRC models are developed for isothermal conditions. This study aims to develop a new WRC model describing the effect of temperature on suction. Based on an assumption of an isotropic and homogeneous porous medium at the macroscopic scale, the formulations of non‐isothermal suction account for the temperature effects on the surface tension of the water–air interface and air bubble shape. The tension of the water–air interface is expressed as a function of temperature, and the air bubble shape becomes a function of temperature and saturation degree. The suction formulations are then used to extend the van Genuchten equation to non‐isothermal conditions. The final equation of the proposed model is a function of suction, and effective degree of saturation and temperature. A laboratory test was also designed to measure the WRCs of a loamy sand at different temperatures. The proposed model was validated against the measured results as well as experimental data of clayey‐silt sand, Boom clay and FEBEX bentonite reported in the literature. The very good agreements show the capability and feasibility of the model to predict the temperature dependence of water retention behaviour with a wide range of soils.Highlights
A new WRC model was developed for non‐isothermal conditions.
The model considers temperature effects on water surface tension and air bubble shape.
We tested the model against measured and literature data, with very good agreements.
The model is applicable to predict non‐isothermal water retention behaviour of unsaturated soils.
The Chinese government has promoted Sponge City construction in the last five years. The premise for a “Sponge City” was based on the problem of accumulation and rapid discharge of various stormwater and water-environment issues during the urbanization process in China. With reference to the expansion of stormwater management in other developed countries, this study summarizes related research results in China. Unlike other stormwater management systems put forward by other countries, such as low impact development, water sensitive urban design, etc., this study investigates stormwater issues at the current developmental stage in China and comprehensively considers the integrated objectives, including water ecology, water security, water resources, water environment, and water culture. Aimed at transforming the traditional extensive urbanization model, it builds on the existing integrated system at the core of stormwater management, which connects with the sewage and / or water supply, and other related systems. This study describes and summarizes the Sponge City’s key fundamentals, targets, technical systems, and extensional relations to guide the further construction of Sponge City and provide important references for other countries.
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