Julio Ángel Infante Sedano

Modified Ring Shear Apparatus for Unsaturated Soils Testing

This paper presents the design details of an automated modified ring shear apparatus for the testing of unsaturated soils using the axis-translation technique. The components of this automated system are described, as well as the types of tests that it can be used for. The key cell components include a flushing system and a precise volume gage system. The paper presents typical test results including the continuous monitoring of water as the test proceeds. A methodology to correct the water content measurements for the effect of air infiltration and evaporation or condensation of water is included.

Well-balanced central-upwind scheme for a fully coupled shallow water system modeling flows over erodible bed

Intense sediment transport and rapid bed evolution are frequently observed under highly-energetic flows, and bed erosion sometimes is of the same magnitude as the flow itself. Simultaneous simulation of multiple physical processes requires a fully coupled system to achieve an accurate hydraulic and morphodynamical prediction. In this paper, we develop a high-order well-balanced finite-volume method for a new fully coupled two-dimensional hyperbolic system consisting of the shallow water equations with friction terms coupled with the equations modeling the sediment transport and bed evolution.The nonequilibrium sediment transport equation is used to predict the sediment concentration variation. Since bed-load, sediment entrainment and deposition have significant effects on the bed evolution, an Exner-based equation is adopted together with the Grass bed-load formula and sediment entrainment and deposition models to calculate the morphological process. The resulting 5 × 5 hyperbolic system of balance laws is numerically solved using a Godunov-type central-upwind scheme on a triangular grid. A computationally expensive process of finding all of the eigenvalues of the Jacobian matrices is avoided: The upper/lower bounds on the largest/smallest local speeds of propagation are estimated using the Lagrange theorem. A special discretization of the bed-slope term is proposed to guarantee the well-balanced property of the designed scheme. The proposed fully coupled model is verified on a number of numerical experiments.

Experimental investigation of the relationship between the critical state shear strength of unsaturated soils and the soil-water characteristic curve

Abstract This paper presents the comparison of experimental results of the critical state shear strength of an unsaturated glacial till and the predicted shear strength using the Soil-Water Characteristic Curve (SWCC), determined following three different techniques, namely: (i) the conventional SWCC without application of any consolidation stress; (ii) the SWCC measured on a specimen subjected to a net stress equal to the net normal stress of experimental shear tests; (iii) the SWCC derived from the degree of saturation and matric suction of the sheared specimen under critical state conditions. The results of the study suggest that the best predictions of the shear strength are possible using the experimental SWCC information expressed as an apparent SWCC. The study also suggests that the relationship between the apparent degree of saturation and the matric suction of a specimen sheared to critical state is unique, and is not influenced by the shearing mode, or compaction water content (i.e. soil structure).

A coupled two-dimensional numerical model for rapidly varying flow, sediment transport and bed morphology

ABSTRACT This paper presents a coupled two-dimensional model that can produce a more stable numerical simulation of rapid bed evolution than the conventional decoupled model. To solve the coupled bed-load sediment transport terms using a Godunov-type central-upwind method, a novel scheme to estimate the bed-load fluxes which can produce more accurate results than the previously reported coupled model is proposed using a pair of local wave speeds different from those used for the flow. The two-dimensional shallow water equations are used to solve the flow velocities and water depth. The bed level is solved by an Exner-based equation containing bed-load sediment transport as numerical flux terms and sediment entrainment and deposition as source terms. Analytical formulas to compute the eigenvalues of the Jacobian matrix are developed. The linear reconstruction of variables with a multi-dimensional slope limiter, and the second-order Runge-Kutta scheme are employed to achieve higher accuracy in space and time. For the case of rapid bed-erosion, the accuracy and stability of the proposed coupled model are verified by several numerical tests.

Three-dimensional shallow water system

We study a three-dimensional shallow water system, which is obtained from the three-dimensional NavierStokes equations after Reynolds averaging and under the simplifying hydrostatic pressure assumption. Since the three-dimensional shallow water system is generically not hyperbolic, it cannot be numerically solved using hyperbolic shock capturing schemes. At the same time, existing simple finite-difference and finite-volume methods may fail in simulations of unsteady flows with sharp gradients, such as dam-break and flood flows. To overcome this limitation, we propose a novel numerical method, which is based on a relaxation approach utilized to hyperbolize the three-dimensional shallow water system. The extended relaxation system is hyperbolic and we develop a second-order semi-discrete central-upwind scheme for it. The proposed numerical method can preserve lake at rest steady states and positivity of water depth over irregular bottom topography. The accuracy, stability and robustness of the developed numerical method is verified on five numerical experiments.

Assessment and comparison of PHCs removal from three types of soils (sand, silt loam and clay) using supercritical fluid extraction

ABSTRACT Supercritical fluid extraction (SFE) was applied to investigate the removal of petroleum hydrocarbons (PHCs) from contaminated soils. Per an initial set of tests for different extraction modes and time durations, the combination of 10 min static mode followed by 10 min dynamic mode, repeated for 3 cycles for a total time of 60 min resulted in the highest PHCs removal percentages. SFE experiments were performed at 33 MPa pressure and 75°C temperature to investigate the influence of soil texture and grain size. Three types of soils were formed and then were spiked with diesel fuel with a ratio of 5 wt%. Soil A, B and C had different particle sizes and were categorized as sand, silt loam and clay, respectively. Soil A (sand) which had the largest particle size resulted in the highest total petroleum hydrocarbon fractions (TPHF), sum of PHC F2, F3 and F4 fractions, removal percentage (90.4%) while soil C (clay) with the smallest particle size and the highest clay content led to the lowest TPHF removal percentage (47.4%). PHC F2 removal percentage for soil A (sand) was 27.3% greater than soil B (silt loam), and the removal efficiency for soil B was 20.4% higher than soil C (clay). While a similar trend was observed for the extraction of PHC F3, the extraction efficiency of PHC F4 for soil A, B and C were not statistically significant. Regarding soil A (sand), the extraction efficiency for PHC F2, PHC F3 and PHC F4 were 98.4%, 92.7%, and 50.2%, respectively. For soil C (clay), the removal efficiency of all PHC fractions were not statistically different. GRAPHICAL ABSTRACT

Closure to “A coupled two-dimensional numerical model for rapidly varying flow, sediment transport and bed morphology” by XIN LIU, JULIO ÁNGEL INFANTE SEDANO and ABDOLMAJID MOHAMMADIAN, J. Hydraulic Res. 53(5), 2015, 609–621

The Authors would like to express their appreciation of the constructive comments provided by the Discussers. The clarifications by the Authors are given as follows. In the Introduction section of their paper, the Authors mentioned that physical decoupling and numerical coupling are two important aspects to be considered when simulating rapid bed evolution under shallow water flows, and that their study focuses only on the numerical coupling in order to achieve a stable and accurate numerical method for rapid bed evolution. Compared to previous studies, which are also based on physically decoupled models (Castro Díaz, Fernández-Nieto, & Ferreiro, 2008; Cordier, Le, & Morales de Luna, 2011; Hudson & Sweby, 2003; Murillo & García-Navarro, 2010; Serrano-Pacheco, Murillo, & Garcia-Navarro, 2012), the aim of the Authors’ paper was to develop a novel numerical method which avoids excessive numerical diffusion while maintaining the numerical stability for the rapid bed-load transport. In order to emphasize the superiority of the proposed numerical method through the comparisons, the Authors used the same physically decoupled model as in the previous studies (Castro Díaz et al., 2008; Cordier et al., 2011; Hudson & Sweby, 2003; Murillo & García-Navarro, 2010; Serrano-Pacheco et al., 2012). Therefore, the Authors would like to clarify that, in Liu, Infante Sedano, and Mohammadian (2015) the novel numerical methods are developed for accurately and stably simulating bed-load transport with capacity assumption. No special numerical technique is developed for suspended sediment transport, which is only included for presenting a general water–sediment-bed model. The Authors agree with the Discussers that, in order to consider the physical coupling, additional terms with regards to mass and momentum exchange between sediment and water flow should be considered in the hydrodynamics model. One of such complete physical coupling models can be found in Cao, Pender, Wallis, and Carling (2004) and Wu (2007), i.e.:

Using the Continuously Disturbed Line to Estimate the Mechanical Behaviour of Unsaturated Compacted Soils

A simple technique which approximates the continuously disturbed line (CDL) using the relationship between water content and matric suction of compacted fine-grained soils, or apparent continuously disturbed line (CDLa) is presented. The CDL is defined as the relationship between a soils water content and suction reached by a soil specimen sheared under constant water content conditions (Croney and Coleman, in J Soil Sci 5(1):75–84, 1954). The critical state line (CSL), generated from specimens sheared under constant net normal stress, and the approximate continuously disturbed line (CDLa) appear to overlap at higher suction values. From plots of water content against matric suction, the CSL appears as a bi-linear relationship which lies below the CDLa with a shallower slope at lower matric suctions. The intersection point of the CSL and CDLa corresponds to the point where a unique value of the microstructural water content, ewm, can be back-calculated from the shear strength data. The relationship between the void ratio and the water content of compacted specimens provides an indication of the moisture content when the air entry value is reached.

One Dimensional Numerical Simulation of Bed Changes in Irrigation Channels using Finite Volume Method

A one-dimensional Saint Venant model is developed using the Einstein sediment transport formula for simulating hydraulics and bed changes in irrigation channels . The governing equations are discretized using Finite Volume Method. The Central-Upwind method is used in this study to calculate the numerical flux. The model gives a stable and good prediction of sub, super and transcritical flows and captures harp changes such as hydraulic jump without leading to numerical oscillation or diffusion. An experimental test case is adopted to examine the performance of this mode. The simulated results show a good agreement with experimental data in the upstream section, and can predict an average value of measured profile in the downstream section of a steep channel. The knick point movement is successfully predicted by the model. The model appears to be a potential and reasonably accurate tool to predict bed changes in irrigation channels due to the water flow.

Integrated Air Trap and Volume Gauge for Axis Translation Systems

This Technical Note presents the design detail of a combined air trap and volume gauge burette used for flushing air bubbles from under ceramic disks in axis translation systems that are used to measure or apply matric suction to unsaturated soil specimens. Axis translation systems are commonly used in the testing of unsaturated soils to subject soil specimens to matric suction values greater than 1 atm. Diffused air may come out of solution and accumulate below the ceramic disk of the axis translation system, prompting to provide a flushing system to remove them. An apparatus consisting of two concentric glass tubes, alongside a graduated scale, two water vessels permitting the isolation of the water phase to reduce moisture exchange with the surrounding atmosphere, and connected to the flushing groove below the ceramic disk of the axis translation system through two plastic tubes was developed. The apparatus described permits an accurate measurement of the volume of water expelled from the specimen and can allow for the volume of diffused air flushed out.