Experimental Assessment of the Sprinkler Application Rate for Steep Sloping Fields

The Programa para el Manejo del Agua y del Suelo (PROMAS) assists the local farming community in introducing new types of locally available irrigation equipment that are both inexpensive and water efficient. Field experiments enabled determining the maximum application rates that cause zero runoff for slopes above 16% for low-cost sprinkler systems.     

Mitigation of Liquefaction-Induced Lateral Deformation in a Sloping Stratum: Three-dimensional Numerical Simulation

Finite-element (FE) simulations are increasingly providing a versatile environment for conducting lateral ground deformation studies. In this environment, mitigation strategies may be assessed in order to achieve economical and effective solutions. On the basis of a systematic parametric study, three-dimensional FE simulations are conducted to evaluate mitigation by the stone column (SC) and the pile-pinning approaches. Mildly sloping saturated cohesionless strata are investigated under the action of an applied earthquake excitation. For that purpose, the open-source computational platform OpenSees is employed, through a robust user interface that simplifies the effort-intensive pre- and postprocessing phases. The extent of deployed remediation and effect of the installed SC permeability are investigated. The influence of mesh resolution is also addressed. Generally, SC remediation was found to be effective in reducing the sand stratum lateral deformation. For a similar stratum with permeability in the silt range, SC remediation was highly ineffective. In contrast, pile pinning appeared to be equally effective for the sand and silt strata permeability scenarios. Overall, the conducted study highlights the potential of computations for providing insights toward the process of defining a reliable remediation solution.     

Eigenvalue Problem from the Stability Analysis of Slopes

Of the existing methods for the three-dimensional (3D) limit equilibrium analysis of slopes, none can simultaneously satisfy all six equilibrium equations. Except for Fellenius’ method that satisfies only one condition of moment equilibrium, all these methods could encounter numerical problems in their applications. Based on the global analysis procedure that considers the whole sliding body instead of individual columns as the loaded body, it is shown that the 3D limit equilibrium analysis of slopes simply reduces to the solution of a generalized eigenvalue problem in which the largest real eigenvalue is just the factor of safety (FOS). The proposed solution is rigorous and can accommodate any shape of slip surfaces. Under undrained conditions, the problem has a unique solution and the FOS has an explicit expression. In addition, through transforming the volume integrals over the sliding body into the boundary integrals, the proposed method does not need to partition the sliding body into columns.     

Antiplane (SH) Waves Diffraction by a Semicircular Cylindrical Hill Revisited: An Improved Analytic Wave Series Solution

An improved accurate closed-form wave function analytic solution of two-dimensional scattering and diffraction of antiplane SH waves by a semicircular cylindrical hill on an elastic half space is presented. In the previous solution, stress and displacement residual auxiliary functions were defined at the circular interface above and below the circular hill. The method of weighted residues (moment method) was used to solve for the unknown scattered and transmitted waves by requiring each term of Fourier series expansion of these auxiliary residual functions to vanish. It was found that the stress residual amplitudes on both (left and right) rims of the hill (ideally should be zero) are not numerically insignificant, irrespective of how many terms used. It was pointed out that the shear stress at the rim is infinite, and that the stress auxiliary function is discontinuous at both rims of the hill, exhibiting a problem for the numerical solution that is more complicated than Gibbs’ phenomenon. The problem with the overshoot of the stress residual amplitudes at the rim was most likely numerical. In this paper, all displacement and stress waves were expressed as cosine functions, and the solution of the circular hill problem was reformulated in this paper, and, for the solution to be correct, the computed stress and displacement residual amplitudes were shown to be numerically negligible everywhere, including those at both rims of the hill. Displacements at higher frequencies are also computed.     

Block Element Method for the Seismic Stability of Rock Slopes

The seismic stability analysis of rock slope is implemented using a block element method (BEM) in this paper. Based on the formulations of the matrices of stiffness, mass, and damping, the dynamic governing equation for the rock block system is established. The Wilson method is used to solve the dynamic governing equation, and the viscoelastic artificial boundary condition is introduced to treat the unbound domain problem. The proposed method is applied to the seismic stability analysis of the intake slope in a hydropower project, from which the dynamic safety factors of key block element combinations during earthquake and their dynamic amplification factors of acceleration are evaluated.     

Relative Buoyancy Dominates Thermal-Like Flow Interaction along an Incline

This paper describes laboratory investigations of the motion between two fixed volumes of dense fluid (surge-type gravity currents) with different salt concentrations that interact above an incline in the presence of ambient stratification. The experiments include both large and small density contrasts between the interacting surges. Initially, the propagation of each fluid mass assumes a thermal-like nature, but then the lower density surge is quickly caught up by the denser fluid flow because of its higher velocity. There are two key process regarding the surge interaction. With a large density contrasting the fluid volumes, the denser flow moves to the front of the current as an intrusion with no mixing. With a small density difference, pronounced mixing occurs between the surges with the development of a homogeneous underflow. A simple energy parameterization is developed to evaluate the source conditions under which the different flow dynamics develop.     

Taxonomy of interpolation constraints on recursive subdivision surfaces

Published online: 14 May 2002     

基于ABAQUS的土质边坡渐进性破坏数值模拟

具有裂隙性、膨胀性等特性的土质边坡稳定性研究需要考虑渐进性破坏问题。采用基于ABAQUS的有限元强度折减法,进行变形局部化和滑动面渐进式形成过程的有限元数值模拟,获得土质边坡稳定性的安全系数,及边坡坡角和土的剪胀角对边坡安全系数的影响。     

膨胀土渠道边坡的破坏与防治对策

膨胀土边坡的破坏在工程中极为常见,它是岩土工程的一个难题。当前对其破坏形式和破坏机理仍未形成统一的认识,影响了问题的解决。在对膨胀土地层结构分析的基础上,通过两个大型的现场试验,并结合许多滑坡实例,概括出膨胀土坡两种典型的滑动形式,即浅表层的膨胀型滑动(塌坡)和中深部的裂隙性滑坡,对膨胀土边坡的破坏有了新的认识。并分析了滑动的机理和影响因素,并对相应的处治对策提出了建议。