Seepage Loading Research Articles

Assessing nutrient concentrations and field-scale seepage load under an automated drainage water management system in Ohio

Automated drainage water management (ADWM) leverages technological advancements to control flow volumes and nutrient loads leaving farm fields through the ADWM system outlet while also promoting lateral groundwater seepage through the edge of the field (EOF). The main objective of this study was to assess the impact of ADWM on nutrient concentrations, namely total nitrogen (TN) and total phosphorus (TP), in groundwater and soil water sampled within and across the EOF for an agricultural field located in northcentral Ohio. Water samples collected from shallow groundwater wells showed that TP and TN concentrations were higher at the EOF relative to in the field while water samples collected from suction lysimeters showed that TP and TN concentrations were higher in the field relative to at the EOF. Further, seasonal nutrient loads across the EOF as lateral groundwater seepage were estimated using an application of the Riparian Flow-Concentration Integration method. We found that the maximum contribution of flow volume and nutrient load across the EOF as lateral groundwater seepage occurred in Spring while minimum contributions occurred in the Winter compared to other seasons of the year. The ADWM system considered in this study, which was programmed to automatically open based on water level rise in the outlet structure, appears to achieve the greatest potential for reductions in nutrient load during Winter by altering flow pathways from the drainage system through the EOF.

Degradation of soil arching caused by suffusion in gap-graded soils

To investigate evolution of soil arching during suffusion in gap-graded soils, a new suffusion apparatus was developed for trapdoor tests under a horizontal seepage flow. Glass beads with fine-grain contents ranging from 15% to 45% were adopted to represent coarse-grain controlled soils and fine-grain controlled soils. Coupled computational fluid dynamics (CFD) and discrete element method (DEM) models were developed to further investigate the evolution of soil arching from microscopic views. At the early stage of suffusion, soil arching degraded rapidly under seepage loads in both coarse-grain controlled and fine-grain controlled soils due to the compaction of soil skeleton and the clogging of voids, which increased in the number of fine particles connected to the stress-transfer matrix. At the later stage, soil arching was nearly maintained as the soil skeleton became stable in the coarse-grain controlled soils. In the fine-grain controlled soils, soil arching degraded continuously due to continuous loss of fine particles connected to the stress-transfer matrix. The decrease in the contact number of fine particles also made the soil skeleton more vulnerable to suffusion. The degradation of soil arching resulted in an increase of surface displacement and a decrease of soil arching height in fine-grain controlled soils.

Long-term deformation and damage analysis of marine clay around seawalls under coupled dynamic-seepage loading

The long-term deformation characteristics and damage degree of soft marine-deposited clay must be evaluated to safely design seawalls. According to abundant field evidence, soft marine-deposited clay tends to experience coupled dynamic loading and seepage loading. Determining the critical load and damage index for these complex loading conditions is imperative. With Tianjin marine-deposited clay as an example, we employed an improved cyclic triaxial instrument to analyse the cumulative plastic strain, water discharge and stress–strain relationship of the clay to understand its long-term deformation development. Based on shakedown theory, the critical cyclic stress ratio (CSR) was determined. A multi-factor damage variable method was proposed to evaluate the damage degree. Its comparison with a traditional mono-factor damage variable method illustrated that this method is effective for damage analyses of marine clay around seawalls under coupled dynamic-seepage loading.

Flume tests and corresponding numerical simulation of hydraulic/mechanical behavior of Tangjiashan landslide dam subjected to seepage loading

Landslide dams (LDs) are usually composed of natural debris materials and normally exhibit heterogeneous strata along both the depth and run-out directions. In addition, LDs usually have weaker structures than undisturbed ground and are more vulnerable to seepage loading. Considering that the surface layer of naturally packed LD materials is mostly in an unsaturated state, it is undoubtedly important to investigate the hydraulic/mechanical behavior of LDs with heterogeneous strata subjected to seepage loading. In this paper, a systematic flume test program was firstly conducted, in which the Tangjiashan LD was carefully referenced for its model design. Three different water level rising rates and two different stratal arrangements were considered in the flume tests. Then, soil-water-air coupled finite element analyses were conducted to simulate the flume tests, and all the material parameters of the LD materials were carefully determined based on the results of element tests. A comparison of the test and calculated results showed the possibility of using the proposed numerical method to predict the occurrence of dam breaching and to estimate the risk of LD failure. Moreover, the hydraulic/mechanical behavior of the LD materials and the heterogeneous strata of the LD were proven to be very important to the stability of the LD. Finally, from an engineering viewpoint, the possibility of utilizing a naturally formed LD, and not destroying it after its formation, is also discussed.

Experimental Study of Seepage Characteristics of Filling Structures in Deep Roadway

In order to study the seepage failure mechanism of roadway filling medium consisting of cohesive soil under complex hydrogeological conditions, a large-scale triaxial stress-seepage test system was utilized to investigate the influence of kaolin content and seepage loading rate on the seepage characteristics of filling medium. Through the analysis on the variation rules of sand loss and particle size distribution, the seepage characteristics and whole process of seepage instability of filling medium were explored in depth. It is concluded that (1) The seepage instability process of filling medium can be categorized into three stages: the initiation loss of fine clay, the accelerating loss of soil, and the stable status of soil loss. (2) The seepage failure process rate is proportional to the seepage loading rate and inversely proportional to the content of kaolin. (3) The kaolin and sand content of remaining mixture presented initial>bottom>middle>top status. The research results have guidance value for exploring the instability evolution mechanism of filling medium in deep roadway.

Analytical Computation of Sandy Slope Stability under the Groundwater Seepage and Earthquake Conditions

Groundwater and earthquake are two of the factors behind the occurrence of slope instability. This paper focuses on the computation of the safety factor acting on a sandy slope when subjected to groundwater seepage and earthquake load. Based on the theory of limit equilibrium and a pseudodynamic method of analysis, a general solution for the dynamic factor of sandy slope containing two load conditions is proposed. In the solution, the effects of parameters such as water level, seismic acceleration coefficients, slope angle, and soil internal friction angle on the slope stability have been discussed. In order to evaluate the validity of the present formulation, the dynamic factors of safety computed by the present method are compared with those given by other cases. It is found that the results of the present method are in good agreement with those of the previous method. The results indicate that the dynamic of safety factor increases linearly with an increase in the soil internal friction angle but decreases with the slope angle and groundwater level and that the effects of direction and magnitude of the seismic inertia forces on the dynamic safety factor of sandy slope are different at different times.

Stability analysis of the air-cushioned surge chamber of the diversion system for San Gabán III hydropower station through seepage-stress coupling approach

The design scheme of the air-cushioned surge chamber is adopted for the diversion system of the San Gabán III hydropower station. Due to the combined action of both high internal water pressure and external water pressure, it is necessary to demonstrate the stability of the design scheme of the air-cushioned surge chamber. This paper adopts the seepage-stress coupling analysis method to analyse the two working conditions of the air-cushioned surge chamber, i.e., the construction condition and the normal operation condition. A fine numerical analysis model of the air cushion surge chamber including the drainage holes and the drainage belts is established. The numerical simulation adopts the one-way coupling scheme. Firstly, the actual seepage fields in the air-cushion surge chamber area under the actual waterhead boundary conditions are numerically simulated. Secondly, the equivalent seepage volume forces are calculated based on the seepage fields obtained. After that, the equivalent seepage forces are applied to the surrounding rock of the air-cushion surge chamber to carry out the mechanical simulations. Results show that, most of the seepage loads are borne by the surrounding rock mass because of the drainage effects. While the pore pressure differences between the inner and outer edges of the lining are dramatically reduced, which greatly reduces the load borne by the lining and ensures the stability of the lining structure. In general, the surrounding rock deformations of the air-cushion surge chamber are not large, the stress states are normal, the supporting structures are within the bearing capacities, and the plastic zones of the surrounding rock are within the control range of the rock bolts, indicating that the air-cushioned surge chamber is stable.

Static And Seismic Stability Analysis of Small Hydraulic Structure Under Seepage Load: A Case Study of Rawanduz Dam

The analysis of the reservoir-dam-foundation coupled system is much more complicated than that of the structure alone because of the difference between the characteristics of the foundation and concrete dam. The small hydraulic structure may be built in seismically active regions, where ground movement would impose earth pressures. The safety of these structures should be investigated quite critically by logical and precise methods. Rawanduz dam subjected to EL-Centro earthquake-S00E component excitation was chosen as a typical case of study. The static and dynamic stability of the Rawanduz dam had been analyzed and evaluated. A 2-D Finite Element model employed using ANSYS software to simulated dam response. The water was modeled as an additive mass according to the theory of Westergaard on the back of the dam while leaving the rest of the reservoir inactive. The dam body is presumed homogeneous, elastic, and isotropic properties for mass material. The soil was assumed to be flexible and analyzed as a nonlinear material. When assessing the stability of the structure under the influence of the seepage loads, the structure was founded safe because the exit gradient value was equal to (0.25), which was less than the critical value of the exit gradient (1/6). Results showed that the principal stresses at the heel and toe of the dam were founded important to study the stability. The static and dynamic analysis findings indicate that the stress values are very low, hence satisfy the normal criteria for protection factors relating to the tensile and compressive strength of the concrete.

Assessment of the Bearing Capacity of Foundations on Rock Masses Subjected to Seismic and Seepage Loads

It is usual to adopt the seismic force acting as an additional body force, employing the pseudo-static hypothesis, when considering earthquakes in the estimation of the bearing capacity of foundations. A similar approach in seepage studies can be applied for the pore pressure’s consideration as an external force. In the present study, the bearing capacity of shallow foundations on rock masses considering the presence of the pseudo-static load was developed by applying an analytical solution for the Modified Hoek and Brown failure criterion. Calculations were performed adopting various inclinations of the load and the slope on the edge of the foundation, as well as different values of the vertical and horizontal components of the pseudo-static load. The results are presented in the form of charts to allow an affordable and immediate practical application for footing problems in the event of seismic loads or seepages. Finally, and to validate the analytical solution presented, a numerical study was developed applying the finite difference method to estimate the bearing capacity of a shallow foundation on a rock mass considering the presence of an additional horizontal force that could be caused by an earthquake or a seepage.

Dynamic responses of loess tunnels with different cross sections under the action of earthquakes, rainwater seepage and trains

Four tunnel models with different cross sections were established, and the models were coupled with fluid models to investigate rainwater seepage-, earthquake- and train-induced effects. The displacements, stresses and pore water pressures of key points in the loess tunnels were analyzed, and the dynamic response patterns of loess tunnels under the influence of earthquakes, rainwater seepage and train loading were obtained. The results show that the dynamic responses of loess tunnels with different cross sections vary. Although the patterns of acceleration and displacement in the four loess tunnel sections are basically identical, the peaks of acceleration and displacement are lowest in the circular tunnel and highest in the rectangular tunnel. Furthermore, obvious stress differences exist among the different sections. The stress is lowest in the circular loess tunnel, intermediate in the curved-wall and straight-walled arch tunnels, and highest in the rectangular tunnel. The pore water pressures of loess tunnels increase with increasing depth, but the differences are not large. Shaking-table testing of a curved tunnel was carried out, and the results were consistent with the numerical results.

Analysis of unsteady seepage field and surrounding rock stability of underground cavern excavation

During the cavern excavation, the underground seepage boundaries are constantly changing, and the seepage field is in an unstable state. Meanwhile, most underground caverns are not constructed with grouting curtains and drainage holes during excavation. The caverns are subject to high osmotic pressure, which is prone to water inrush and seepage failure. Based on the Signorini’s type variational inequality, the variable bandwidth iteration method is proposed to effectively simulate the potential overflow boundary in unsteady seepage by loosing restrictions for non-overflow nodes. The advantage of this methods over traditional methods is fast convergence and relatively high accuracy. Subsequently, a simulation method of unsteady seepage field in the cavern excavation process is proposed, and following this we applied the corresponding unsteady seepage load to the surrounding rocks to evaluate the stability of the cavern. The above methods were further applied to the excavation process of Azad hydropower station powerhouse. The results show that during the cavern excavation, the groundwater surface gradually decreases and the flow rate of the cavern generally increases. In addition, although the osmotic load has an adverse effect on the stability of the cavern, the impact is not significant. This research has proofed guiding significance for maintaining stability throughout the underground cavern excavation process.

Experimental Investigation of the Deformation Characteristics of Tianjin Clays under Coupled Dynamic Stress and Seepage Fields

The causes, prevention, and control of clay disasters are of great concern in practical engineering applications. Recently, due to unprecedented economic development, increasing numbers of tunnels and subgrades of tidal flat areas have been built in Tianjin, China. Soft soil ground not only bears the vibration load during operation and construction but also receives seepage effects caused by the bursting of pipelines and variations in groundwater levels. Under the coupling action of dynamic and seepage loads, large settlement can occur in soft soil since the deformation is related to both cyclic stress and seepage. Therefore, it is significant to understand the dynamic deformation characteristics of soil to ensure the safety of engineering applications. In this study, a series of laboratory cyclic triaxial tests were conducted to study the deformation behaviours of Tianjin clays under coupled cyclic stress and seepage fields. To simulate the seepage field, water pressure is applied at the bottom of the specimen, and the water can be drained from the top of the specimen to form a head difference in the specimen during the tests. The effects of the seepage pressure, cyclic stress ratio (CSR), and a number of cycles (N) on the hydraulic conductivity, axial deformation, hysteresis curve and dynamic modulus of Tianjin clays were systematically investigated. The laboratory results show that the hydraulic conductivity (k) decreases with the increasing seepage pressure, CSR, and N, and its range is from 4.6 × 10−8 cm/s to 7.4 × 10−8 cm/s. The axial deformation of the soil increases with increasing CSR and seepage pressure. With an applied water pressure of 150 kPa at the bottom of the specimen and a CSR of 0.3, the maximum cumulative plastic strain reaches 4.78%, increasing by 53.2% compared with a CSR of 0.1. The hysteresis curve gradually becomes denser or thinner with increasing CSR and N; the hysteretic curve tends to a straight line for N of 5,000. The dynamic modulus increases with increasing N and depends on the CSR and seepage pressure. Empirical equations are suggested for calculating the dynamic modulus with different CSR values and seepage pressures. The results of this study can provide reference parameters for the construction and design of tunnels and subgrades of tidal flat areas in clay strata under the influence of water environments.

Influence of stress anisotropy on stress distributions in gap-graded soils

The behaviour of gap graded soils comprising non-plastic fines (sand or silt) mixed with a coarser sand or gravel fraction has received attention from researchers interested in internal instability under seepage loading (a form of internal erosion) as well as researchers interested in load:deformation responses. Skempton and Brogan [1] postulated that resistance to seepage induced instability depends upon the proportion of the overall applied stress that is transmitted by the finer fraction. Shire et al. [2] explored Skempton and Brogan’s hypothesis using DEM simulations to look at the proportion of the applied stress transmitted by the finer fractions (α) in ideal isotropic samples. They showed that at low fines contents (FC< FC*) the average stress transmitted by the finer grains is less than the applied stress (α<1), while for FC>FC+ the fines play a key role in stress transmission (α>1); for FC*<FC< FC+, α depends on the sample density. The current contribution describes a series of constant p’ DEM triaxial test simulations carried out to assess the evolution of stress heterogeneity with shearing. The simulation data generated indicate that a sample can transition from being fines dominated (with the fines transmitting a significant proportion of the applied stress and α ≥1) to coarse or sand- dominated (with α <1) as the material dilates during shear deformation. While α reduces as the samples dilate, the relationship between the α and the sample void ratio is non-trivial. The anisotropy of the coarse-coarse contact network exceeds the overall contact force anisotropy; this indicates that the deviator stress is transmitted through a strong force network passing through the coarse-coarse contacts supported by the fine-coarse contacts.

Failure mechanism of unsaturated landslide dam under seepage loading – Model tests and corresponding numerical simulations

Due to the rapid cracking, sliding and packing of its geomaterials, a landslide dam (LD) is usually weaker in structure than the undisturbed ground and is more vulnerable to seepage loading. In addition, since the naturally packed geomaterials of an LD are mostly in an unsaturated state, it is necessary to use a suitable constitutive model that can describe the mechanical behaviour of the soils under an unsaturated/saturated state in a unified way and whose material parameters can be determined in a rational way in order to accurately simulate the failure mechanism of the LD. In this paper, water retention tests and flume tests were conducted on model LDs prepared with three different ground materials. An unsaturated soil constitutive model was selected for the corresponding numerical simulations. Based on the results of water retention tests and triaxial tests, the parameters of the LD materials were properly determined. Using these parameters, soil-water-air coupling finite element analyses were conducted to simulate the flume tests on the model LDs. By comparing the calculated results with the test results, it was found that the numerical method used in this paper has satisfactory accuracy for describing the different failure mechanisms of the model LDs under seepage loading. The results indicate that the material properties of the LDs, especially the strength and the difference in void ratio between the unsaturated and the saturated states, play important roles. In addition, the influence of the rate of the rise in water head was also investigated by numerical tests. The purpose of this research is to provide a scientific basis for decision-making in the disaster mitigation process of LDs with a comprehensive method for understanding the failure mechanism of these LDs.

Rice Drain Management to Reduce Seepage Exports in the Sacramento-San Joaquin Delta, California.

Many deltas worldwide face subsidence issues due to increased anthropogenic activity. The Sacramento-San Joaquin delta similarly faces ongoing subsidence, more than 8 m in some areas, that increases levee failure risks and threatens the security of this water source for 25 million California residents and 1.2 million ha of agriculture. Rice ( L.) fields are an integral part of a proposed new strategy for managing subsidence because they have been shown to stop subsidence and provide an alternative crop for growers. Two important considerations for implementing rice fields are additional water requirement and the effect on water quality from mobilized dissolved organic carbon (DOC) and disinfection byproduct precursors. To understand constituent transport and potential management opportunities for rice farming, a plug flow reactor mass balance model was used to quantify surface and subsurface hydrologic pathways. Management of adjacent drainage ditch water levels under low and high scenarios were tested as a strategy to reduce seepage and water quality loads. Under high drains, groundwater met 10% of evapotranspiration (ET). Low drains resulted in a 100% increase in ET demand, which was met by surface water applied for irrigation. High drains reduced subsurface seepage by 95%. Subsurface DOC, trihalomethane, and total dissolved nitrogen loads were reduced 10-fold in high drains compared with low drains. Flow rate accounted for 74 to 90% of load variance and was the primary determinant of constituent loads. Thoughtful implementation of rice cultivation, with high water levels in adjacent drains, can be leveraged to reduce irrigation water demand and constituent load outputs.

An analytical solution for design of pressure tunnels considering seepage loads

• In this paper, an analytical solution is proposed, for design of pressure tunnels. • The problem is considered as axial-symmetric. • The medium is assumed to be poroelastic, homogeneous and isotropic. • The applicability of it is illustrated by using illustrative example problems. In a pressure tunnel with a permeable lining, development of flow from the tunnel induces seepage stresses in the surrounding ground and the lining. In this paper, an analytical solution for analysis and design of pressure tunnels is presented, based on a generalized effective stress principle. The problem is considered as axial-symmetric, and the lining and the rock mass are assumed to be poroelastic, homogeneous and isotropic. The proposed method covers various types of pressure tunnels, such as unlined, shotcrete lined, concrete lined, reinforced concrete lined and prestressed concrete lined pressure tunnels. For unlined and uncracked lined pressure tunnels, the hydraulic analysis is independent of mechanical responses; thus, closed-form expressions for stresses, strains and pore pressure are derived. On the other hand, in cracked reinforced concrete linings, the development of cracks are considered in the mechanical and hydraulic responses. In this case, the hydraulic and mechanical analyses are coupled; therefore, the hydraulic and mechanical analyses are carried out by an iterative procedure. The applicability of the proposed solution for the design of pressure tunnels is illustrated and discussed by using an illustrative example problem.

Wave Interaction with Porous Vertical Breakwater in Two-layer Fluid

In this paper, the two-layer fluid model is used to investigate the wave interaction with porous vertical breakwater resting on permeable seabed in two-layer fluid. Based on the Biot seepage consolidation theory and linear wave theory, the analytical solutions to the wave potentials and the seepage pressures inside permeable seabed induced by surface wave and inner wave are derived by applying eigenfunction expansion approach. And accordingly, the analytical expressions of wave-induced uplift force and overturning moment acting on the bottom of porous breakwater are obtained. Numerical results are presented to illustrate the seepage loads caused by inner wave may have same order of magnitude as that induced by surface wave, and the wave-induced seepage loads may have the same order of magnitude as direct wave loads. It is found that the porosity of the breakwater surface may lead an obvious reduction in direct wave loads on breakwater and a certain reduction in wave-induced seepage loads on the bottom of breakwater, especially, lead to a significant reduction in the inner wave-induced overturn moment.

The Seepage Numerical Simulation of High-Pressure Sway-Sprinkle Reinforced Hongze Lake Embankment

The paper uses saturated - unsaturated seepage calculation of FEM, analyzes the seepage numerical of hongze lake dike reinforced by high-pressure Sway-sprinkle technology, provides seepage load for stress and deformation and stability calculation of the dike engineering, evaluates the anti-seepage effect of high-pressure sway-sprinkle cutoff wall. The results show that it reduced invasion of the embankment surface and decreased seepage velocity and flow, high-pressure sway-sprinkle cutoff wall took good effects and greatly improved the overall stability and safety of hongze lake dike.

Multi-Scale Model Of Dam Safety Condition Monitoring Based On Dynamic Bayesian Networks

Abstract In order to monitor dam safety condition better, a Dynamic Bayesian Networks (DBN) model is developed to overcome the shortcomings of the ordinary monitoring methods in this paper. Ordinary methods include comprehensive assessment methods and numerical simulation methods. Comprehensive assessment methods have shortcomings such as weight detemunation, scale difference, variables correlation, etc. In addition, comprehensive assessment methods cannot describe the multi-scale characteristics of monitoring data and dynamic property of large dam. Numerical simulation methods need complex mathematical theory, mechanics methodologies and high performance computer. DBN is a novel model with the consideration of correlations, delay and multi-scale characteristics of the variables such as deformation, seepage, stress and water load and temperature loads, as well as duration at every state. And the new model is also a simpler method with less experience, computational complexity and fewer experiments compari...

Seepage Field Study of Xiaowan Hydropower Project

The Xiaowan Hydropower Project is located in the middle and lower reaches of the Lancang River in Yunnan Province, China. The arch dam of this project, with a height of 294.5m, is by far the highest dam of its type that has been completed in the world. The great water potential makes it necessary to assess the seepage behavior in the dam-foundation system. Due to the complexity of geological conditions and seepage control system, the research is full of challenges. In this paper, the finite element method (FEM) is adopted to simulate the three-dimensional seepage field. The initial flow method and the boundary pre-adjustment method are combined to obtain the seepage free surface and overflow surface under complicated boundary conditions. The hydraulic potential contours, seepage gradient, drainage discharges, and so on, are all analysed and the results show that the seepage control system is reasonable and effective. Furthermore, the results of the seepage field can provide suitable seepage load in the stress-strain and stability analysis for the dam-foundation system of Xianwan. At present, the project is in good operation.