This paper firstly introduces the distribution of weathered layers, and then presents the relationship between watercontent and expansive force and the working model of expansive forces in expansive soil slopes. Takin...This paper firstly introduces the distribution of weathered layers, and then presents the relationship between watercontent and expansive force and the working model of expansive forces in expansive soil slopes. Taking the expansive soil slope ofJing-Yi Expressway as example and applying the Slices Method, this paper puts forward the stability calculation method con-sidering the effect of expansive forces, and also proposes the treatments.展开更多
Soils with strain-softening behavior — manifesting as a reduction of strength with increasing plastic strain — are commonly found in the natural environment. For slopes in these soils,a progressive failure mechanism...Soils with strain-softening behavior — manifesting as a reduction of strength with increasing plastic strain — are commonly found in the natural environment. For slopes in these soils,a progressive failure mechanism can occur due to a reduction of strength with increasing strain. Finite element method based numerical approaches have been widely performed for simulating such failure mechanism,owning to their ability for tracing the formation and development of the localized shear strain. However,the reliability of the currently used approaches are often affected by poor convergence or significant mesh-dependency,and their applicability is limited by the use of complicated soil models. This paper aims to overcome these limitations by developing a finite element approach using a local arc-length controlled iterative algorithm as the solution strategy. In the proposed finite element approach,the soils are simulated with an elastoplastic constitutive model in conjunction with the Mohr-Coulomb yield function. The strain-softening behavior is represented by a piece-wise linearrelationship between the Mohr-Coulomb strength parameters and the deviatoric plastic strain. To assess the reliability of the proposed finite element approach,comparisons of the numerical solutions obtained by different finite element methods and meshes with various qualities are presented. Moreover,a landslide triggered by excavation in a real expressway construction project is analyzed by the presented finite element approach to demonstrate its applicability for practical engineering problems.展开更多
A plant is stabilized by its root system. In congested urban cities such as Hong Kong, ground trenching is frequently seen due to the installation of utility lines along the roadside. Soil nailing, which involves soil...A plant is stabilized by its root system. In congested urban cities such as Hong Kong, ground trenching is frequently seen due to the installation of utility lines along the roadside. Soil nailing, which involves soil coring in slopes, is a common solution to improve the slope stability. However, both activities inevitably pose a risk to the integrity of any root sys- tems present, and thus reduce the root anchorage. To prevent or minimize such damage, a careful design of the excava- tion/drilling location is of prime importance. Ground penetrating radar （GPR） provides a non-destructive method for locating roots by examining the contrast between the dielectric properties of the roots and the surrounding soil. To examine the perfor- mance of GPR and promote its use in Hong Kong, a test bed was prepared using local materials to create a controlled envi- ronment in which to conduct a series of systematic tests evaluating the performance of a 900 MHz GPR. The reflected radar- grams were subject to the influence of the following factors： size and depth of roots, horizontal distance between roots, and contrast between the root and soil water content. Correlations between root size and a number of waveform parameters were also explored. Limiting values for root size, root embedded depth, horizontal separation distance between roots, and water content contrast between root and soil were obtained. A significant correlation was found between the root diameter and time travel parameter T2 （p〈0.001, t=0.795）. Because GPR root detection is highly site-specific, this study provides a local refer- ence for GPR performance in the Hong Kong environment. The findings demonstrate that the 900 MHz GPR is applicable in Hong Kong for the detection of main roots.展开更多
文摘This paper firstly introduces the distribution of weathered layers, and then presents the relationship between watercontent and expansive force and the working model of expansive forces in expansive soil slopes. Taking the expansive soil slope ofJing-Yi Expressway as example and applying the Slices Method, this paper puts forward the stability calculation method con-sidering the effect of expansive forces, and also proposes the treatments.
基金funded by the Chinese National Basic Research Program (2010CB731503)
文摘Soils with strain-softening behavior — manifesting as a reduction of strength with increasing plastic strain — are commonly found in the natural environment. For slopes in these soils,a progressive failure mechanism can occur due to a reduction of strength with increasing strain. Finite element method based numerical approaches have been widely performed for simulating such failure mechanism,owning to their ability for tracing the formation and development of the localized shear strain. However,the reliability of the currently used approaches are often affected by poor convergence or significant mesh-dependency,and their applicability is limited by the use of complicated soil models. This paper aims to overcome these limitations by developing a finite element approach using a local arc-length controlled iterative algorithm as the solution strategy. In the proposed finite element approach,the soils are simulated with an elastoplastic constitutive model in conjunction with the Mohr-Coulomb yield function. The strain-softening behavior is represented by a piece-wise linearrelationship between the Mohr-Coulomb strength parameters and the deviatoric plastic strain. To assess the reliability of the proposed finite element approach,comparisons of the numerical solutions obtained by different finite element methods and meshes with various qualities are presented. Moreover,a landslide triggered by excavation in a real expressway construction project is analyzed by the presented finite element approach to demonstrate its applicability for practical engineering problems.
基金the Research Grants Council of the Hong Kong Special Administrative Region (HKSAR) (Grant Nos. HKUST9/CRF/ 09, HKUST6/CRF/12R)
文摘A plant is stabilized by its root system. In congested urban cities such as Hong Kong, ground trenching is frequently seen due to the installation of utility lines along the roadside. Soil nailing, which involves soil coring in slopes, is a common solution to improve the slope stability. However, both activities inevitably pose a risk to the integrity of any root sys- tems present, and thus reduce the root anchorage. To prevent or minimize such damage, a careful design of the excava- tion/drilling location is of prime importance. Ground penetrating radar （GPR） provides a non-destructive method for locating roots by examining the contrast between the dielectric properties of the roots and the surrounding soil. To examine the perfor- mance of GPR and promote its use in Hong Kong, a test bed was prepared using local materials to create a controlled envi- ronment in which to conduct a series of systematic tests evaluating the performance of a 900 MHz GPR. The reflected radar- grams were subject to the influence of the following factors： size and depth of roots, horizontal distance between roots, and contrast between the root and soil water content. Correlations between root size and a number of waveform parameters were also explored. Limiting values for root size, root embedded depth, horizontal separation distance between roots, and water content contrast between root and soil were obtained. A significant correlation was found between the root diameter and time travel parameter T2 （p〈0.001, t=0.795）. Because GPR root detection is highly site-specific, this study provides a local refer- ence for GPR performance in the Hong Kong environment. The findings demonstrate that the 900 MHz GPR is applicable in Hong Kong for the detection of main roots.
