Visual Simulation of Soil-Structure Destruction with Seepage Flows

This paper introduces a method for simulating soil-structure coupling with water, which involves a series of visual effects, including wet granular materials, seepage flows, capillary action between grains, and dam breaking simulation. We develop a seepage flow based SPH-DEM framework to handle soil and water particles interactions through a momentum exchange term. In this framework, water is seen as a seepage flow through porous media by Darcy's law; the seepage rate and the soil permeability are manipulated according to drag coefficient and soil porosity. A water saturation-based capillary model is used to capture various soil behaviors such as sandy soil and clay soil. Furthermore, the capillary model can dynamically adjust liquid bridge forces induced by surface tension between soil particles. The adhesion model describes the attraction ability between soil surfaces and water particles to achieve various visual effects for soil and water. Lastly, this framework can capture the complicated dam-breaking scenarios caused by overtopping flow or internal seepage erosion that are challenging to simulate.

Hydraulic conductivity behavior of soilcrete specimens created from dredging sand, cement, and bentonite

Dredging sand is an inexpensive material utilized to rise elevations of highway embankments and earth levee bodies in the Southern Vietnam. However, high permeability of the dredging sand can cause failures due to seepage flows during annual flood seasons. The dredging sand mixing cement with or without bentonite is expected to be suitable low permeability as an impermeable material. However, hydraulic conductivity of soilcrete and bentonite specimens created from dredging sand taken in the Mekong delta has limit research data. This study aims at better understanding the hydraulic conductivity of dredging sand samples taken in Dong Thap province mixed with cement and bentonite. The effects of the hydraulic conductivity of soilcrete and bentonite soilcrete specimens on time, cement contents, bentonite contents, cement types, and hydraulic gradients were investigated. The tests followed the ASTM D5084 standard using the both falling head-constant tailwater and falling head-rising tailwater methods. The results indicate that: (1) the hydraulic conductivity of the soilcrete and bentonite specimens decreased with increasing in testing duration and cement contents; (2) the hydraulic conductivity of the soilcrete specimens was lower 104 to 105 times than that of the compacted sand; (3) the hydraulic conductivity of the bentonite soilcrete specimens was lower 10 times than those of the soilcrete specimens; (5) the PCS cement can induce long-term reduction of soilcrete hydraulic; (6) effect of hydraulic gradients on soilcrete hydraulic conductivity was ignorable; (6) the soilcrete hydraulic conductivity varies from 10− 9 to 10− 10 m/s.

Anisotropy Properties of Turbulence in Flow Over Seepage Bed

The present study analyses the Reynolds stress anisotropy in the non-uniform sediment beds under the condition of no seepage and downward seepage flow. The results show the estimation of the deviation measure from the isotropic turbulence in view of Reynolds stress tensor for turbulent flow in the presence of seepage through the channel bed. The investigation presents the Lumley triangle for flow turbulence, Eigen values, and the invariant functions for the whole flow depth subjected to no seepage and seepage beds. The longitudinal profile of anisotropy tensor within the near-bed zone for seepage flow provides the higher anisotropic stream than those of no seepage flow, while the remaining (transverse and vertical) profiles of anisotropy tensor in the vicinity of bed for seepage flows provides lower anisotropic stream. The anisotropic invariant maps show the near bed anisotropy inclining to be a two-component isotropy subjected to no seepage and seepage flow. With the increase in vertical distance from bed surface that is close to the water surface, the data sets of anisotropic invariant maps for no seepage and seepage flows show a trend of one-component isotropy, while it has an affinity to develop a three-component isotropy in the vicinity of mid zone of the flow depth. Invariant function data sets present a well two-component isotropy in the near bed region of flow and a quasi-three component isotropy in the outer region of flow for seepage flows as compared to no seepage flow.

Impacts of Consolidation Time on the Critical Hydraulic Gradient of Newly Deposited Silty Seabed in the Yellow River Delta

The silty seabed in the Yellow River Delta (YRD) is exposed to deposition, liquefaction, and reconsolidation repeatedly, during which seepage flows are crucial to the seabed strength. In extreme cases, seepage flows could cause seepage failure (SF) in the seabed, endangering the offshore structures. A critical condition exists for the occurrence of SF, i.e., the critical hydraulic gradient (icr). Compared with cohesionless sands, the icr of cohesive sediments is more complex, and no universal evaluation theory is available yet. The present work first improved a self-designed annular flume to avoid SF along the sidewall, then simulated the SF process of the seabed with different consolidation times in order to explore the icr of newly deposited silty seabed in the YRD. It is found that the theoretical formula for icr of cohesionless soil grossly underestimated the icr of cohesive soil. The icr range of silty seabed in the YRD was 8–16, which was significantly affected by the cohesion and was inversely proportional to the seabed fluidization degree. SF could “pump” the sediments vertically from the interior of the seabed with a contribution to sediment resuspension of up to 93.2–96.8%. The higher the consolidation degree, the smaller the contribution will be.

The problem of the flow of fluid to an imperfect drill hole

This article studies seepage flows arising from the selection of hydrocarbons from imperfect drill-holes. The authors observe the problem of pressure field in a homogeneous isolated isotropic homogeneous reservoir perforated in the range, completely contained in the layer of a common width.<br> To construct an analytical asymptotic solution, the single-layer initial problem is replaced by an equivalent three-layer symmetric, including the piezoconductivity equations for the perforated, covering, and underlying non-perforated layers, the initial and boundary conditions; on the conditional boundary of the perforated and non-perforated layers, the conditions of pressure and flow equality are specified (conjugation conditions). The solution of the problem is assumed to be regular&nbsp;— the value of the desired function, and, if necessary, its derivative at infinity is zero.<br> The problem is formulated in dimensionless quantities for the functions of the pressure deviation from its unperturbed distribution, normalized to the amplitude value of the depression. To solve the problem, the authors have developed an asymptotic method of a formal parameter. The solution of the problems for the zero and first coefficients of the asymptotic expansion is found in the space of the Laplace&nbsp;— Carson images in the variable <i>t</i>.<br> Based on the formulas obtained and the Darcy law, the authors construct graphical depen­dencies for the vertical and horizontal components of the fluid velocity filtered from the periphery to the well.<br> The computational experiment illustrates that there are no vertical flows at the exit to the well in the perforated part of the reservoir, and when removed from the well, these flows are different from zero, which indicates the presence of interlayer flows even in homogeneous imperfect drill holes. In the center of the perforated layer, such flows are absent, since the transverse velocity component vanishes. At the same time, the inflow in an imperfect drill hole is uneven, and the maximum modulus of the horizontal velocity component on all curves is reached at the boundary of the perforation interval.