Translational upper bound limit analysis of shallow landslides accounting for pore pressure effects

Many rainfall-induced landslides are reported to be shallow. Therefore, when regional slope stability analysis, or landslide hazard mapping is carried out, simple approaches, such as the infinite slope model, are often used. However, the infinite slope model is known to underestimate the factor of safety due to the absence of boundary effects. More sophisticated methods that account for the boundary effects at the toe and head of the landslide are much more computationally expensive. In this paper upper bound limit analysis (UBLA) is presented with a novel failure mechanism which consists of a translational parallelogram in the middle slope and two log-spiral components at the slope crest and slope toe to capture the boundary effect. The new approach is derived for a full range of pore water pressure conditions and validated by finite element limit analyses. For shallow landslides the translational UBLA is found to outperform the conventional log-spiral UBLA. The results of a large parametric study using the translational UBLA are then used to develop a novel analytical shallow landslide model which retains the simplicity of the traditional infinite slope model, but yet improves accuracy considerably, making this an attractive alternative for routine analysis such as landslide hazard mapping

Design and modeling of an on-site greywater treatment system for a hotel building

As the United States is making a significant move towards rejoining the Paris Agreement on climate change, there is a high demand for sustainable solutions across various industries, including construction and hospitality sectors. The aim of this project was to design and model an on-site greywater treatment system for a hotel building for the effective reuse of sewage water. The study considered Los Angeles, California, as a case study location and referred to respective climate conditions and construction standards. This study considered various options of greywater treatment plants such as Membrane Bioreactor (MBR), Sequencing Batch Reactor (SBR), and Reverse Osmosis with Upflow Anaerobic Sludge Blanket (RO with UASB) which were carefully reviewed and modeled through the GPS-X software. The design and modeling results were verified by hand calculations and were followed by the estimation of capital and operational expenses required for the implementation of the plants. Having relatively low capital and operational expenditure requirements as well as superior technical performance, the MBR plant proved to be the most effective solution for the considered location and standards and was recommended for use in hotel buildings

Stability and consolidation of sediment tailings incorporating unsaturated soil mechanics

YesTailing dams are commonly used to safely store tailings without damaging the environment. Sand tailings (also called Sediment tailings) usually have a high water content and hence undergo consolidation during their placement. As the sediment tailings are usually placed above the ground water level, the degree of saturation and permeability of the sediment tailing is associated with the unsaturated condition due to the presence of negative pore-water pressure or suction. Current practices normally focus on the analyses saturated conditions. However, this consolidation process requires the flow of water between saturated and unsaturated zones to be considered. The objective of this study is to investigate the stability and consolidation of sediment tailings for the construction of road pillars considering the water flow between saturated and unsaturated zones. The scope of this study includes the unsaturated laboratory testing of sediments and numerical analyses of the road pillar. The results show that the analyses based on saturated conditions overestimate the time required to achieve a 90% degree of consolidation. The incorporation of the unsaturated soil properties is able to optimize the design of slopes for road pillars into steeper slope angles

A Synoptic- and Remote Sensing-based Analysis of a Severe Dust Storm Event over Central Asia

Published by [Verlag nicht ermittelbar], Taina

Review of Suspended Sediment Transport Mathematical Modelling Studies

YesThis paper reviews existing studies relating to the assessment of sediment concentration profiles within various flow conditions due to their importance in representing pollutant propagation. The effects of sediment particle size, flow depth, and velocity were considered, as well as the eddy viscosity and Rouse number influence on the drag of the particle. It is also widely considered that there is a minimum threshold velocity required to increase sediment concentration within a flow above the washload. The bursting effect has also been investigated within this review, in which it presents the mechanism for sediment to be entrained within the flow at low average velocities. A review of the existing state-of-the-art literature has shown there are many variables to consider, i.e., particle density, flow velocity, and turbulence, when assessing the suspended sediment characteristics within flow; this outcome further evidences the complexity of suspended sediment transport modelling

Flood Suspended Sediment Transport: Combined Modelling from Dilute to Hyper-concentrated Flow

YesDuring flooding, the suspended sediment transport usually experiences a wide-range of dilute to hyper-concentrated suspended sediment transport depending on the local flow and ground con-ditions. This paper assesses the distribution of sediment for a variety of hyper-concentrated and dilute flows. Due to the differences between hyper-concentrated and dilute flows, a linear-power coupled model is proposed to integrate these considerations. A parameterised method combining the sediment size, Rouse number, mean concentration, and flow depth parameters has been used for modelling the sediment profile. The accuracy of the proposed model has been verified against the reported laboratory measurements and comparison with other published analytical methods. The proposed method has been shown to effectively compute the concentration profile for a wide range of suspended sediment conditions from hyper-concentrated to dilute flows. Detailed com-parisons reveal that the proposed model calculates the dilute profile with good correspondence to the measured data and other modelling results from literature. For the hyper-concentrated profile, a clear division of lower (bed-load) to upper layer (suspended-load) transport can be observed in the measured data. Using the proposed model, the transitional point from this lower to upper layer transport can be calculated precisely

Numerical Modelling of Pipe Loading Using a Linear Interpolation Method

The movement of pipe in sand and clay are presented, formulated and analyzed using a linear interpolation method within the framework of elastic perfectly plastic Mohr Coulomb criteria and a new two-mechanism non-associative piecewise linear Drucker Prager formulation. The two mechanisms are found when the variation of shear strength due to mean effective stress is separated from that due to plastic deviatoric strain. The modelling framework is intended to show thedeformation and displacement of soil surrounding pipe. Furthermore it also describes the relationship between displacement and the force. Horizontal and vertical displacement are applied into pipe and they are modelled using finite element program, CRISP version 4. Slip element (interface) is attached in the vicinity of pipe to compare the deformation produced in this case with those without interface.Different material properties of cohesive and granular soil taken from laboratory tests are set in the model. All main parameters are recorded from lateral and horizontal loading test, as a part of the Collaborative Project on Soil/Pipe Interaction Mechanisms and Modelling. Application of the approach are presented and discussed with emphasis on identifying and optimizing some of the important factors that control the displacement of soil because of the movement of pipe. Several conclusions are drawn regarding the difficulties encountered in the numerical implementation. Illustrative numerical results 'for common geotechnical experiments on clay and sand using finiteelement software demonstrate the stable derivation of the two linear non associative Drucker Prager model

Soil–water characteristic curves of gap-graded soils

Soil–water characteristic curves (SWCCs) of compacted mixtures of residual soil and gravel with different particle sizes were determined from laboratory tests. The study involved compacted mixtures of 50% residual soil by dry mass and 50% gravel of different particle sizes. The compacted mixtures were gap-graded in grain–size distribution with bimodal characteristics, but their SWCCs did not exhibit a bimodal characteristic. The gap-graded nature of the grain–size distribution of the mixtures did not affect the conventional sigmoidal shapes of the SWCCs. The pore-size distribution of the mixtures indicated that large pores within the compacted mixtures were filled with fine-grained soils. The air-entry value of the compacted mixtures was found to be high due to the high dry density of the specimens. The different particle sizes of the gravel used in the mixtures resulted in a variation of air-entry value of the mixtures. The dry density and coefficient of uniformity of the grain–size distributions were found to affect the air-entry values of the mixtures and the SWCC fitting parameters n and m, respectively. The variation of SWCC fitting parameters n and m showed significant correlations between grain–size distribution and pore-size distribution of the mixtures, whereas the SWCC fitting parameter a was not the air-entry value of soil

Robust analysis and design of bored pile considering uncertain parameters

Many high-rise buildings and bridges in the worlds are constructed using bored pile. To provide a safe design of this type of deep foundation, high-quality soil data are needed which are normally obtained from laboratory testing. However, the contractor and the consultant often conduct only a limited field testing without performing laboratory tests. As a result, the capacity of bored pile may deviate from the real value. This study aims to develop a framework for analysis and design of axial and lateral capacity of bored piles when only a few soil parameters are known. The proposed methodology uses analytical methods backed by numerical calculations according to relevant code of practice. The results indicate that as long as the analytical results are supported by the numerical calculations, a robust design can be achieved with only a few soil parameters: a standard penetration test and a cone penetration test