Hydraulic Slope Research Articles

Combined effects of rainfall and flow depth on the resistance characteristics of sheet flow on gentle slopes

Rainfall and sheet flow (SF) on gentle slopes always appear concurrently. However, the combined effects of rainfall and flow depth on SF resistance are still unclear for gentle slopes. In this study, two sets of experiments, namely, upstream inflow with rainfall and upstream inflow only, were conducted to investigate the resistance characteristics of SF on a flat and smooth flume with three gentle slopes (3°, 5° and 7°). The experimental results indicated that in the tests with upstream inflow only, the Darcy–Weisbach resistance (f) and Manning coefficient (n) decreased following a power function with increasing flow depth. When the Reynolds number (Re) was less than 1070, the n and f of the SF in the upstream inflow alone decreased with increasing Re following the power function. Both the n and f of the SF increased with increasing rainfall intensity for the upstream inflow with the rainfall tests. The rainfall significantly affected the f and n of the SF in the low Re zone (Re < 1070), inflow discharge (<0.06 m2 min−1) and flow energy for all inflow with rainfall cases. Under the conditions of upstream inflow with rainfall, both the f and n of the SF decreased with the increase in the ratio between the flow depth and median raindrop diameter (H/D50) in the power function. This result indicated that a deeper flow could dissipate more raindrop energy. In addition, empirical equations among Re, hydraulic slope and H/D50 were established to predict the n and f of the SF for upstream inflow with rainfall tests. This study will be helpful in understanding the combined effects of rainfall and flow depth on SF and could provide a scientific basis for improving hydrological and soil erosion models.

Study on Critical Hydraulic Gradient Theory of Flow Soil Failure in Cohesive Soil Foundation

The current formula of critical hydraulic gradient is not adapted to solve critical hydraulic gradient of cohesive soil. Assume that the seepage failure mode of the cohesive soil foundation was cylindrical or inverted circular truncated cone, based on the calculation formula of the critical hydraulic gradient of Terzaghi, the analytical formula of the critical hydraulic gradient considering the influence of the shear strength of the soil was derived. Then, the seepage failure process of the clay layer was simulated numerically, and the effects of the clay layer thickness, failure radius, and shear strength indexes on the critical hydraulic slope were analyzed. The comparison results show that the numerical test results are in good agreement with the calculated results of the new formula. In addition, the critical hydraulic gradient of sandy loam and loess under different working conditions was studied severally by a self-made permeation failure instrument. The results show that the critical hydraulic gradient decreases with the increase of soil thickness and failure radius, and the maximum error between the test and the corresponding formula results is no more than 16%.

Freeze-Up Ice Jam Formation in the River Bend, a Case Study on the Inner Mongolia Reach of Yellow River

Concern has been expressed regarding the impacts of climate change on river ice and ice jam formation in cold regions. Ice jams are easily initiated in bends and narrow channels and cause disasters. In this study, observations and remote sensing monitoring are used to study the freeze-up ice jam formation of bends. Sediment transport and freezing process of the river interact, influencing bed changes profile and sedimentary budget. River ice processes, channel evolution, ice hydro-thermodynamics, and ice jam accumulation are explored. The results show that the channel topography determines the river thalweg, and that the channel elevation interacts with the river ice through sediment transport. The channel shrinkage increases the probability of ice jam, and the sharp bend is prone to ice jam formation. Under the effect of secondary circulation flow in the bend and in the outer bank, the juxtaposed freeze-up and the hummocky ice cover occur in the same location, and frazil ice accumulates under the junction of the main channel and the shoals. Affected by the increase of the hydraulic slope and the velocity downstream, open water reaches develops downstream of the ice accumulation. An open water section is emerged upstream of the bend, due to the ice deposition, and partly cut-off supply of the frazil.

Taking into account the spatial variability of the physical and mechanical properties of a hydraulic dump when flushing it

Introduction. Slope stability analysis reliability depends on the level of schematizing the results of engineering-geological survey, hydrogeological monitoring, electrical sounding, and mine surveying data generalization. In order to improve the stability analysis accuracy, it is relevant to use the geomechanical models, which take into account the spatial variability of the adjacent rock mass physical and mechanical properties, with further search for the most hazardous section in the plan. Research aim is to substantiate the relevance of slopes physical and mechanical monitoring by the methods of downhole control and further stability analysis with the use of the geological and geophysical models. Methodology includes the search for the most hazardous section of the rock mass by the ratio of the shearing and restraining forces within the limits of the established zones characterized by the variability of physical and mechanical properties. Results. As a result of generalizing the databases of the engineering and geological study, hydrogeological monitoring, electrical sounding and mine surveying, the volumetric geological and geophysical models were built of the technogenic massif formed at the dump, as well as the slopes of the hydraulic overburden face, represented by the three-level fill of dry overburden. Test areas stability has been analyzed for the actual position, and the comparative analysis of the results was made. Conclusions. When building volumetric geological and geophysical models of man-made rock masses formed at the areas of filled hydraulic waste diposals, in addition to the results of the traditional survey measurements and direct engineering and geological study, it is important to create informative databases on spatial and temporal variations of physical and mechanical properties of alluvial rock conditioned by their fluid loss and consolidation, which with in details at cross hole intervals may be obtained based on the statistical dependences on electrical conductive properties variation by the methods of electrical sounding or tomography; and when making enclosing embankments (bridges) of dry rocks – information about excess pore pressure under these facilities. When using the hydromechanized method for the alluvial rocks, relatively homogeneous in strength properties, the hydraulic overburden face slope stability is determined to the greatest extent by the absolute values of the accumulated strength indicators in the mined area and the unfavorable combination of the edge shape (the presence of protruding sections and face unevenness in the plan) with the entry height. The established range of the stability coefficient was n = 1.03–3.76. The stability of the enclosing structures made of dry rock to the greatest extent depends on weak alluvial layer depth and thickness and the absolute value of excess pore pressure in this layer. The established range of stability coefficient variation for this rock mass section is much narrower and amounted to n = 1.29–1.59.

Сравнение результатов расчета гидравлического уклона самотечных сетей водоотведения по классической и уточненной формуле А. Шези

In the present work, we compare the calculation results by the classical Antoine Chézy formula and refined Prodous - Shlychkov formula. Unlike the classical formula for the hydraulic calculation of gravi-ty drainage networks introduced in 1769, the new formula includes the thickness of an actual deposit layer in pipe water troughs. Using the A. Chézy formula for the hydraulic calculation of new pipes made of different materials provides sufficient practical accuracy; however, no studies have been per-formed for pipes with deposits in the water troughs. The Chézy formula is characterized by the de-nominator having the reduced pipe diameter, which takes into account the effect of the thickness h associated with a sediment layer. To compare the precision of the two formulas, a practical problem should be solved. For that, a specific example is necessary to compare the calculation results of hy-draulic slope i, obtained using the classical Chézy formula and refined Prodous - Shlychkov formula. Analysis of the values of pipe characteristics indicates that the presence of a deposit layer h = 0.1 m in the water troughs leads to an increase in the gravity flow rate from Vn = 0.88 m/s to Vpr = 2.0 m/s (2.27 times) and the hydraulic slope from in = 0.00282 m/m to ipr = 0.02527 m/m (8.96 times). Therefore, in-troducing the dpr value to the formula allows more accurate results in the hydraulic calculation of the hydraulic slope ipr to be obtained for pipes with deposits in their water troughs. An example of hydrau-lic calculation for pipes with deposits and the dependency graph of the hydraulic slope as a function of the actual flow rate are provided. The obtained values are summarised in a table with pipe characteris-tics depending on different gravity flow rates. It is recommended to introduce the refined A. Chézy formula to the normative standard RR 32.13330.2012.

Сравнительный анализ расчетных зависимостей для гидравлического расчета самотечных сетей водоотведения

In this work, we carried out a comparative analysis of empirical dependences (A. Chézy and N.F. Fe-dorov formulas) for the hydraulic calculation of wastewater gravity flow networks. Using these formulas on a specific example, the hydraulic slope of a gravity pipeline was calculated and the error in the val-ues of the actual hydraulic potential characteristics of the pipes was determined. The data obtained showed that calculations using the Chézy formula ensure the highest accuracy. The A. Chézy formula was revised by introducing the concept of reduced pipe inner diameter. The dependency graph i = f (dpr) was plotted, indicating that the revised version of the A. Chézy formula gives more accurate re-sults than the classical one. The revised A. Chézy formula is recommended for the hydraulic calcula-tion of wastewater gravity flow networks. We proposed developing calculation tables for the hydraulic calculation of wastewater drainage flow networks with internal deposits.

Flow characteristics in open channels with aquatic rigid vegetation

In order to study the flow characteristics in water bodies with rigid aquatic vegetation, series of laboratory experiments are carried out in an open channel, in which glass rods are used as plants with diameters of 6mm, 8mm and 10mm, respectively. For each diameter of glass rods, four typical cases are considered with various densities and arrangements of glass rods. The flow velocities in the four cases are measured by the 3-D laser Doppler velocimeter (LDV). The water surface slope, the flow velocity, the water head loss, the vegetation drag force and the hydraulic slope are calculated, analyzed and discussed. The horizontal, vertical and total vegetation densities in the vegetation area are defined and the relationship between these physical parameters and the water surface slope are studied. The head loss and the hydraulic slope in the vegetation area are also calculated, compared and analyzed. It is indicated that the water surface slope and velocity, the head loss and the hydraulic slope in the vegetation area have a close relationship with the arrangement, the density, and the plant diameter of the vegetation.

Study of the Sediment Transport Law in a Reverse-Slope Section of a Pressurized Pipeline

This article reveals the change law of the head loss and critical deposition velocity during hydraulic transmission of a solid–liquid two-phase pipeline. This article also establishes a physical test model. A single variable is used to conduct the experimental research by changing the conditions of the pipeline flow rate, the sediment concentration, and the reverse slope degree. Based on an analysis of the test process, a new formula is proposed to determine the critical sedimentation rate of the pipeline that considers a change in the adverse slope. By analyzing the variation rule of the hydraulic slope of the pipeline sediment in different states and comparing the hydraulic slope of the horizontal pipeline and reverse pipeline in different states, different factors that influence head loss are revealed. Finally, the measured value of this test is compared with the Durand equation and the Worster equation. It was found that the measured value of this test was more similar to the Durand equation. This study not only provides theoretical support for sand removal in pipelines but also promotes sedimentation in reservoirs.

A Physically Based Method for Real‐Time Monitoring of Tidal River Discharges From Water Level Observations, With an Application to the St. Lawrence River

AbstractA fast, physically based, fully nonlinear, and nonsteady reach‐averaged river model is developed to provide instantaneous freshwater discharge rates in the tidally influenced stretch of the St. Lawrence River (Canada) from water level measurements alone at two tide gauge stations. The model does not require any a priori knowledge of the river geometry (width and depth) or hydraulic conditions (hydraulic slope and friction coefficient) as those parameters are inferred by inverse modeling. The model is fast in that several decades of hourly discharges can be reproduced in few seconds on any modern desktop computer. The method is accurate in that it reproduces to within 3% the observed tidal discharge variability at 8 different cross‐sections distributed along the tidally influenced portion of the St. Lawrence River. Although much simpler, the new method performs as well as, or better than, much more sophisticated models for reproducing daily and monthly discharge averages. Being physically based, it is also shown that the model can perform well outside the limited range of measurements that are generally available for calibration. The method is simple and easy to manage in that the main function only contains a few lines of code such that it could be readily implemented as a tool for real‐time discharge monitoring of the St. Lawrence River near Québec City. Being physically based, the model developed here could likely be applied more generally to highly unsteady tidal rivers with flow reversals.

EFFECTIVE PARAMETERS OF TAIL PROCESSING GOLD-BEARING ORE HYDROTRANSPORT FOR VERNINSKAYA PROCESSING FACTORY

The paper shows that in order to increase the efficiency of hydraulic transport systems in mining the transportation of slurries with a high concentration of solids in the slurry flow. Experimental studies have shown that slurry tailings of gold-containing ore with mass concentration of more than 55% are viscoplastic fluids. Experiments on a rotational viscometer allowed us to establish the main rheological characteristics of the studied slurries. Experimental studies of hydraulic transport performed on a laboratory setup, confirmed the results obtained on a rotational viscometer. Curved mixture streams are inclined straight lines that cut off on the axis of the head the sections, which determine the initial hydraulic slope corresponding to the shear stress yield on the rheological curves. According to the results of the experiments, a method has been developed for calculating the hydraulic transport of highly concentrated slurries of tailings of gold-bearing ore. Head loss values increase with increasing concentration. A sharp increase in head loss occurs in the concentration range from 60 to 65% and above

Cinite Element Analysis of Hydraulic Slope Stability Based on Strength Reduction Method

Slope stability analysis is a hot research topic in geotechnical engineering. According to the actual engineering hydraulic slope stress, based on the strength reduction method theory, the finite element software ANSYS is used to analyze the stability of a hydraulic slope engineering, and the effective safety factor of the slope is obtained, which is safe for other slopes. Support design provides a reference.

Effective Parameters of Tail Processing of Gold-Bearing Ore Hydrotransport for Verninskaya Processing Factory

The article is devoted to the analysis of the composition and properties of the materials and liquids during transportation using pipeline and shows that in order to increase the efficiency of hydraulic transport systems in mining a transition to the transportation of slurries with a high concentration of solids in the slurry flow is necessary. Experimental studies have shown that slurry tailings of gold-containing ore with mass concentrations of more than 55 % are viscoplastic fluids. Experiments on a rotational viscometer allowed us to establish the main rheological characteristics of the studied slurries – shear stress and the dynamic effective viscosity. It has been established that over the entire range of concentrations from 55 to 65 %, the flow of slurries is described by the Bingham rheological equation. Experimental studies of hydraulic transport performed on a laboratory setup with a pipeline diameter of 50 mm confirmed the results obtained on a rotational viscometer. The curved of mixture stream is inclined straight lines that are cut off on the axis of the head in the sections, which determine the initial hydraulic slope corresponding to the yield shear stress on the rheological curves. According to the results of the experiments, a method has been developed for calculating the hydraulic transport of high concentrated slurries of tailings of gold-bearing ore. Calculations showed that in a given range the performance of the hydrotransport system and the mass concentration of the solid phase pressure losses vary from 11 to 84 m of water column/m. Head loss values increase with the increasing concentration. A sharp increase in the head loss occurs in the concentration range from 60 to 65 % and higher.

Hydrogeological characteristics of foot caves in a karst peak-forest plain in South China

In karst areas of South China, isolated peaks in peak-forest plains often have foot caves near the water table. Originally, foot caves are formed by surface water on the plain flowing through the peak foot into the underground during the rainy season. Later, surface water might not flow into some foot caves anymore, but foot caves still connect with groundwater. Understanding the role of foot caves is important in comprehending regional groundwater flow and in controlling the damage caused by groundwater flow in cave sites. This study employed a multi-electrode resistivity method to locate karst voids or caves at Zengpiyan cave site, Guilin City (Guangxi Province). Boreholes were used to detect karst features, tracer tests were adopted to assess the flow path and velocity of groundwater, and hydrological observations were conducted on site to reveal groundwater changes. Of the 26 boreholes drilled, 14 found underground caves, with heights ranging from 0.3 to 17.5 m. Groundwater was stored and flowed in four distinct media zones: concentrated flow zone (CFZ), highly fractured zone, cave sediment zone, and matrix-with-fractures zone, in which the foot caves constitute the primary groundwater flow zone. The CFZ was characterized and found to have a minimum hydraulic slope of 0.2%. Thus, the study succeeded in identifying hydrogeological characteristics of foot caves in a karst peak-forest plain and a hydrogeological model of the foot caves was developed. The methodology provides a basis for flood control and groundwater pollution prevention in the hydrogeological unit in which foot caves are located.

Calculation of the parameters of the hydraulic transport of enrichment waste in polyethylene pipes

In the article, a new method is presented for calculating hydraulic slope and critical speed of cleaning reject hydrotransportation through the polyethylene pipelines, which is based on the Methodology for Calculating Hydrotransport Plants for Tailings Transporting and Inwashing at the Iron Ore Mining and Processing Enterprises. This methodology was approved by the State Construction Committee of the Ukrainian SSR in its Temporary Instructions on Technology of the Tailing Dump Arrangement and was used in the design of all of the waste storage facilities in the Krivyy Rih ore-dressing and processing enterprises. For the conditions of the experiments, it was shown that experimental multiplier in the formula for calculating critical speed of hydrotransportation was depended on the pipeline diameter, free fall acceleration, kinematic coefficient of water viscosity and absolute roughness of the pipe inner surface. The acknowledgement of these factors made an empirical constant in the considered formula dimensionless and close to average value of the constants in the formulas obtained by other similar methods. With the considered method, it is proved that experimental constant in the formula for calculating critical speed of hydrotransportation is inversely proportional to the cubic root of the roughness of the pipeline inner surface, while coefficient of proportionality is a universal constant, which does not depend on the properties of the pipeline material and is equal to 10.1. Therefore, for determining critical speed of hydrotransportation through the polymer pipes by using this method, it is necessary to multiply critical speed for steel pipe with a similar diameter by the cubic root of ratio of roughness of the inner surfaces of the steel and polymer pipelines. It is further shown that value of hydraulic slope significantly depends on the operating coefficient, which shows by how many times coefficient of friction hydraulic resistance in the polyethylene pipe operating in supercritical flow regime exceeds the same value in case of critical flow regime for the same pipe. The research results allowed finding formulas for calculating hydraulic slope and critical speed of the iron-ore cleaning reject hydrotransportation through the polyethylene pipelines, which are based on the dependencies obtained for the steel pipes and value of absolute roughness of the pipeline inner surface.

Coupled hydro-mechanical modelling of a 1995 Hong Kong landslide

The paper deals with the modelling of the instability mechanism induced by rainfall in an unsaturated cut-slope. A large-sized landslide occurred in 1995 in Hong Kong (the so-called “Fei Tsui Road landslide”). It was here analysed because it was characterized by unusual dimensions and very large runout distance for the study area. The slope failure was attributed to a decrease in soil shear strength due to the rise of a perched water table above a weak kaolin-rich layer, together with the loss of suction caused by water infiltration during a heavy rainfall event. The hydro-mechanical coupled analyses made through the commercial software Plaxis 2D aimed to investigate the relations between the hydrological variables (i.e., rainfall infiltration, suction, saturation) and the slope response in terms of changes in soil resistance and soil plastic deformations. The study demonstrates that the evaluation of the hydro-mechanical coupling effects on the hydraulic slope response as well as on the stability of the whole slope is a crucial issue to well capture the mechanical behaviour of the unsaturated cut-slope. Different failure scenarios have been also considered in order to match the field observations and to back-analyse the initial condition of the slope before landslide.

Effect of Compaction and Hydraulic Gradient on Subbase Layer Permeability

In order to prevent or at least reduce the deformation of road surface, it is necessary to ensure adequate water permeability of the structural layers and control of groundwater level. In geotechnical engineering, the water permeability of the mineral aggregates or soils is determined using a constant head water permeability apparatus. In order to assess the suitability of the results, it is necessary to take into account particle size distribution of the test object and perform the test at different hydraulic ramps. The aim of this research is to define and clarify unbound mineral aggregate mixtures hydraulic gradient and compaction level of road layer impact on water permeability. The following properties have been determined during the tests: particle size distribution, particle density, Proctor density, optimum water quantity, water permeability under different compaction and hydraulic slopes. Based on the results of the research, low-dustiness non-bonded mineral materials are recommended for frost resistant layers. For the water-permeability coefficient test, it is recommended that the test layer should be compacted to a design compaction ratio and the hydraulic gradient should not be higher than 1.0. Other conclusions and recommendations for further research and for improvement of water permeability functionality in the road pavement are presented.

Numerical Study on Vertical and Horizontal Seepage Deformation of Silty Soil

In this paper, the PFC3D fluid-solid coupling calculation module is used to simulate the seepage deformation process of silty sand under vertical and horizontal seepage. The seepage mechanism such as particle contact, flow field distribution, critical hydraulic slope and particle motion of silty sand under different seepage direction is analyzed. The numerical simulation results show that the critical hydraulic gradient of silt sand in vertical seepage is higher than the critical hydraulic gradient in horizontal seepage.

Feature Analysis and Control Method of Seepage Deformation of Rock and Soil in Port and Coast

ABSTRACT Wang, S.; Liu, D., and Wang, Z., 2018. Feature analysis and control method of seepage deformation of rock and soil in port and coast. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 436–441. Coconut Creek (Florida), ISSN 0749-0208. It is difficult to effectively reflect seepage deformation features and development process of rock and soil by detecting the seepage hazard of rock and soil and concentrated seepage channel using current seepage deformation feature analysis methods. It cannot directly evaluate the anti-seepage performance of coastal rock and soil. This paper presents a method for analysis and control of seepage deformation of rock and soil in port and coast. By determining the type of seepage deformation of soil and the critical hydraulic slope or the allowable hydraulic slope, it is determined whether the dam foundation is deformed due to seepage by the comparison between the critical hydrauli...

Grading opening and shearing deformation of deep outward-dip shear belts inside high slope: A case study

Tectonic shear belts, with their low mechanical strengths, large spatial extents and obvious shearing damage, present challenges for the excavation of high slopes. In this study, we described the basic unloading performances of shear belts induced by excavation through observational data and numerical back analysis. The unloading deformation and failure processes of deep outward-dipping shear belts exposed on a hydraulic slope nearly 300 m tall were investigated first. The field observation and monitoring data indicated that the excavation-induced deformation pattern of the outward-dipping shear belt can be divided into two stages: primarily opening deformation normal to the shear belt during the first stage and primarily shear deformation along the shear belt during the second stage, manifested as opening and shear cracks along the active shear belt. Then, the numerical and analytical analysis were performed to expose the displacement evolution of the shear belt during the multistep excavation of the slope from the top down. The back analysis showed that the grading deformation mechanism of the shear belt was primarily related to the reduction of normal compressive stress on the shear belt's plane due to slope excavation. The reinforcement schemes, including a prestressed anchor cable to limit deep unloading deformation and a prestressed rock bolt to restrain the surface relaxation of the rock mass of the slope, were also discussed. In practice, actual excavation and corresponding monitoring data indicated that the unloading mechanism and supporting measures for the shear belt presented in this study were reasonable and effective. These presented experiences can also enrich the stability analysis and support design for similar high slopes.

Determination of the critical rate of hydrotransport based on measurements in supercritical flow conditions

The article solves the actual problem of determining the value of the critical rate of hydrotransport for a specific hydrotransport unit in terms of its operation in supercritical flow conditions, without violating the process regulations and the required freight traffic for processing. Based on the analysis and generalization of the known methods of calculating the parameters of hydrotransport, a methodical approach was proposed for determining the value of the critical rate of hydrotransportation according to the dependence of the hydraulic slope on the speed and concentration of the slurry. The efficiency of the developed methodology was proved based on the results of measurements of the parameters of the Vilnohirsk State Mining and Metallurgical Plant hydrotransport complex in supercritical conditions. The reliability of the developed technique is confirmed by the fact that the relative error in determining the critical rate of hydrotransport according to the methods improved by the author does not exceed 7 %, and in determining the hydraulic slope does not exceed 6 %, respectively.