Seepage Problems Research Articles

Evaluation of seepage under hydraulic structures using gene expression programming

The problem of seepage under concrete dams was studied numerically using finite difference code in MATLAB, after verification with GeoStudio (2018 R2) to determine the lift force under the dams, the head at the third floor of each of the dams, and the exit gradients, which all affect the functionality of these dams. The main goal of this study was to investigate the effects of cutoff locations and depths on the exit gradient and uplift pressure. An empirical equation was thus developed to predict the exit gradient by employing gene expression programming (GEP) and non-linear regression using IBM SPSS based on parameters obtained from the finite difference code. Multiple (327) runs were executed in the finite difference code for a set difference between head upstream and downstream (H=10 m) withvarious cutoffs depth (d/b), with kx/ky = 1 representing isotropic soil. For each d/b value, various cutoffs locations (x/b) were also used, with results indicating that the minimum exit gradient is observed when the cutoff location ratio at the downstream is x1/b=1 with a maximum relative depth of d1/b=0.6, while the minimum uplift pressure is observed when the cutoff location ratio at the upstream is x1/B=0, with a minimum relative depth of d1/B=0.1. The results further indicate that the maximum exit gradient is observed when the ratio of the length of upstream cutoff to the length of downstream cutoff is d1/d2 = 1. This exit gradient decrease as the ratio of d1/d2 increases. Additionally, the exit gradient decreases with increases in cutoff location and depth, while increasing with uplift pressure. Based on the simulation results, the equation obtained using the genetic expression programming model performed better in terms of predicting the exit gradient than the SPSS model, with a coefficient of determination R2 of 0.892 for training and 0.90 for testing. An empirical equation was thus derived to predict the exit gradient based on cutoff 1depth, cutoff1location, cutoff2depth and cutoff2location.

Comparison of numerical modeling results from laboratory and field obtained unsaturated flow parameters

Moisture and suction variation beneath pavement contribute significantly to the volumetric deformation of expansive subgrade in response to climatic loading. In order to quantify the damage due to climatic loading, estimation of moisture, and suction variation in pavement subgrade is of paramount importance. The objective of the current study is to investigate the moisture and suction variation in response to precipitation events with the aid of numerical modeling in the unsaturated pavement subgrade. In unsaturated soils where the voids are filled with both water and air, the SWCC describes the volume of the voids that remain filled with water as the soil drains pore water. The SWCC has been identified as the vital soil information required to analyze seepage, stability, and volume change problems involved in unsaturated soils. However, the selection of unsaturated flow parameters is typically laboratory-based which represents specific conditions rather than a dynamic scenario of the field. In this study, an attempt was undertaken to conduct numerical modeling using field generated unsaturated flow parameters along with five other predictive models. Results indicated the distinct variation of moisture and suction distribution in subgrade from the same rainfall event while using laboratory versus field generated SWCC unsaturated flow parameters. In addition, predicted model yielded output was also varying with the field generated parameters’ output. Instead of using laboratory-generated static parameters, it was found that field generated dynamic unsaturated flow parameters were able to capture better suction variation at the pavement subgrade.

COMPARISION AND STUDY OF NUMERICAL METHODS FOR DYNAMIC RESPONSE EVALUATION OF SDOF

Written for senior-year undergraduates and first-year graduate students with solid backgrounds in differential and integral calculus, this paper is oriented toward engineers and applied mathematicians. Consequently, this paper should be useful to senior-year undergraduates the finite element method [1]. The scaled direct approach is adopted for this purpose and each step in the finite element solution process is given in full detail. For this reason, all students must be exposed to (and indeed should master). This paper provides the general framework for the development of nearly all (nonstructural) finite element models. The finite element method of analysis is a very powerful, modern computational tool. Applications range from deformation and stress analysis of automotive, aircraft, building, and bridge structures to field analysis of beat flux, fluid flow, magnetic flux, seepage, and other flow problems. This paper presents study and comparison of numerical methods which are used for evaluation of dynamic response. A Single Degree of Freedom (SDF)-linear problem is solved by means of Newmark’s Average acceleration method [2], Linear acceleration method [2], Central Difference method [6,7] with the help of MATLAB. The advantages, disadvantages, relative precision and applicability of these numerical methods are discussed throughout the analysis.

Potential of soil resources of Coconut Research Station, Aliyarnagar, Tamil Nadu, India for agro-technology generation

Potential of soil resources of Coconut Research Station, Aliyarnagar of Tamil Nadu Agricultural University and one of the Centers of ICAR-AICRP (Palms), was assessed by soil profile examination and spatial variability mapping. Three soil profiles were examined, one each in A, B and C blocks of the farm, soils were studied horizon wise samples were collected, and fertility parameters were analyzed. Spatial variability of primary nutrients was mapped employing GIS techniques. Soil profile examination revealed the presence of canker nodules in the lower horizons and the depth of the soil was not a constraint for the cultivation of perennial crops. The texture of the soil varied from loamy sand to sandy clay loam. pH was alkaline and electrical conductivity was less than 2 dSm-1. The content of KMnO4-N was low, and Olsen P, NNNH4OAc-K and organic carbon were medium. Land capability class was IIIew and was highly suitable (S1) for coconut, moderately suitable (S2) for cocoa and marginally suitable (S3) for pepper. The soil taxonomic class is fine-loamy mixed, isohyperthermic Fluventic/Typic Haplustepts. Rock outcrops were noticed over 5 per cent of the area. Top soil erosion and seepage problems resulting in temporary water logging are the major fertility constraints associated with this farm. Scrupulous application of organic manures, split application of fertilizers, providing trenches in areas of water logging, etc., are the strategies to overcome the constraints, which are existing in the farm.

Slope Failure Investigation in Weathered Granitic Rock Mass Using Electrical Resistivity Imaging: Case Study in Kg Bukit Selar, Jeli, Kelantan, Malaysia

The slope failure phenomenon is a common natural hazard in Malaysia in which due to the change in slope angle, weathering, heavy rainfall, and overloading. This research is focusing on analyzing the subsurface condition of slope failure in Kg Bukit Selar, Jeli, Kelantan by the electrical resistivity imaging (ERI) method. Geologically, the study area mainly composed of granitic rocks (microgranite and porphyritic granite). A total of five resistivity survey lines using Schlumberger and Pole-Dipole array with a 200m spread was conducted at the failed slope. ABEM Terrameter LS was used to collect field data, and processed by using RES2DINV software. The results were presented in the form of two-dimensional (2D) resistivity profiles providing a view of the subsurface distribution of the granitic rock, geological structures, and water content. The results show that the slope failed due to the presence of groundwater. The findings in this study show that the resistivity survey is a reliable method for slope failure investigation. The slope failures due to seepage problems were successfully being investigated using the ERI method.

Mesoscale analysis of the suction stress characteristic curve for unsaturated granular materials

There is still no theoretical framework accounting for linkage between seepage and deformation of unsaturated granular materials. Using a mesoscale liquid bridge model, we propose the first approach for deriving the suction stress characteristic curve (SSCC). Then, we verify the method by obtaining both the soil–water characteristic curve and SSCC for cubic and tetrahedral granular packing. The approach is further validated by generating the SSCCs of granular packings with different particle size distributions. On this basis, a new two-parameter model is suggested that satisfactorily predicts the SSCCs of various real granular materials. The nonlinear variation of strength versus suction is also properly described by a new formula for three kinds of soil. We believe that this SSCC model can help resolve solid–fluid coupling in seepage and deformation problems in unsaturated granular engineering.

Numerical simulation on Time-dependent Behavior and Long-term Safety Analysis of Soft Rock Tunnel under Seepage Condition

This study investigates the time-dependent behavior of soft surrounding rocks of the Shanxi Panxiushan railroad tunnel. Based on the viscoelastic-plastic damage mechanics, the rheological problem, mechanical properties of degradation, and seepage problem of the soft rock tunnel are comprehensively considered. The time-dependent deformation and stress of the surrounding rock mass following excavation were simulated using the proposed model of finite-difference software FLAC3D. The stress distribution of the surrounding rock support and reinforcement after the excavation were obtained. The simulation results show that the rationality of the existing reinforcement scheme is verified and the final deformation stability time of the surrounding rock during the operational period is calculated. Furthermore, a novel damage-based long-term safety analysis method is proposed, providing theoretical guidance and technical support for the design and construction of soft rock tunnels. The factor of safety (FOS) of the surrounding rock during the excavation and operational period is analyzed using the proposed analysis method. These results could have reference value for the design and construction of similar soft rock tunnels.

Accurate Empirical Calculation System for Predicting the Seepage Discharge and Free Surface Location of Earth Dam over Horizontal Impervious Foundation

In the numerical analysis of the Laplace equation, which is the governing equation of the seepage phenomena of homogeneous, isotropic earth dams, it has been confirmed that numerical analysis with high accuracy is possible by using the interpolation finite difference method (IFDM). In a previous paper, based on this numerical analysis method, the equivalent Kozeny (KZ) flow method was proposed as a new empirical method to calculate the seepage discharges and free surface locations of earth dams. Although this method is generally a highly accurate method compared with the empirical method of A. Casagrande, owing to calculating the seepage problems within a few percentages of discharge relative errors, several additional studies are necessary. By integrating the finding of this study to the previous literature, an empirical seepage calculation system with high accuracy, the equivalent KZ flow method, is created. Owing to the finally proposed empirical method, called “interpolation-equivalent KZ flow method”, the discharge and free surface location can be predicted with high accuracy in a wide range.

Damage Model and Experimental Study of a Sand Grouting-Reinforced Body in a Seawater Environment

A water-rich sand layer is a common stratum in marine underground engineering. Grouting is a technology for soil or rock sealing, a method to solve the water seepage problem, and can be used to solve geological challenges in water-rich sand layers. A grouting-reinforced body deteriorates by the long-term erosion of seawater, resulting in attenuation of the performance of the solid. Obtaining the decay law of the performance of the grouting-reinforced body can guarantee the safe operation of the underground structure over a long life cycle. To this end, by describing the solid damage after seawater erosion, the stress–strain curve and the relationship between the damage variable and the internal micro-cracks and pores in the grouting-reinforced body were analyzed. Then, a constitutive model of the solid damage in the seawater environment was established. The stress–strain curve of added solid after deterioration was obtained by designing an indoor grouting reinforcement test and an accelerated deterioration test. Finally, the constitutive model of the sand layer plus solid deterioration in a seawater environment was determined. This research is of great importance for improving the deterioration theory under a seawater environment and ensuring the long term safety of tunnel operations.

Finite Element Analysis of Seepage for Hemrin Earth Dam Using Geo-Studio Software

Finite Element Approach is employed in this research work to solve the governing differential equations related to seepage via its foundation's dam structure. The primary focus for this reason is the discretization of domain into finite elements through the placement of imaginary nodal points and the discretization of governing equations into an equation system; An equation for each nodal point or part, and unknown variables are solved. The SEEP / W software (program) is a sub-program of the Geo-Studio software, which is used by porous soil media to compensate for the problems of seepage. To achieve the research goals, a study was carried out on Hemrin dam, which located in the Diyala River 100 km northeast of Baghdad, Iraq. Thus, one cross-section is selected for different elevations (minimum, normal and maximum or flood design elevations) to compute the seepage of water, pore water pressure and phreatic line. By theoretical analysis appeared that when the water reservoir was connected to the flood level, a problem may occur in the downstream face of the dam lead to seepage failure. A set of solutions checked by using the Geo-Studio software has been suggested in this research to solve this problem. In addition, and by analytical approach SLOPE/W (a sub-program of the Geo-Studio software) are used to assess the stability of the downstream slope and calculation factor of safety.

Case Study on Planning and Execution of Residential Building on Complex Hilly Terrain: Sustainable Perspective

This paper depicts a sustainable approach for the safe and cost-effective construction and design of foundations at Devannapet village, Hasanparthy Mandal of Warangal, Telangana State, India. Owing to the uneven topography of the site, the residential building was proposed to be constructed at a relatively higher slope compared to the road level. The uneven distribution of the soil stratum necessitated the adoption of novel and sustainable site-specific foundation technique. To meet the sustainability criteria, the excessive material obtained from the site during the leveling was utilized as construction material (filling, drainage, and as a component in concrete mix design) and in the design of stone masonry earth retaining structure at the downstream side. The engineering philosophy behind designing such a foundation has been discussed in detail in this paper relying on cost–benefit analysis for various components of the foundation. The seepage and drainage problems at the foundation level have been discussed. The details of reinforcements, stability checks, and the resultant design have been discussed in detail in this manuscript. The sustainable method employed in this article will assist the practicing engineers in designing cost-effective foundations for residential buildings when similar terrains are encountered.

Experimental Study and Engineering Application of Polypropylene Fiber Shotcrete for Bored Tunnels in Water-Rich Strata

During the construction of water-rich bored tunnels, it is important to improve the impermeability of the primary support shotcrete to ensure construction safety. This work considers the underground excavation of water-rich strata in the section between the Baisheng Shaft and Xiba River Station of the Beijing Metro Line 12. A polypropylene fiber-reinforced shotcrete (PFRS) was designed using an orthogonal experimental method. The fiber size and content, cement content, sand rate, and water–cement ratio were the key factors in the PFRS performance. Based on the analysis of the experimental data along with numerical simulations and other research methods, a new mix proportion of PFRS is proposed and successfully applied to engineering sites. It is shown that compared with ordinary shotcrete, the impermeability of PFRS is greatly improved as the maximum can be increased by 42.5%. After the application of PFRS on-site, the problems of water seepage and excessive deformation of the tunnel supporting structure in the water-rich strata were alleviated. This fully ensures the overall stability of the tunnel and provides a guarantee for a safe construction site.

Mechanics model and optimum design of PE pellet shell for anti-water-seepage with ease in open

Polyethylene capsule shells are a kind of container for pills with low cost and long-term preservation, after paraffin-sealed. This kind of pellet shell is composed of two hemispheric shells with the seal convex and concave allowances, at which they connect, locate and unify together as a whole by local elastic deformation. However, the water seepage occurs in certain percentage of the pills during paraffin-seal operation. In order to solve the problem of water seepage and further improve the process, the current study presents the tension model under the action of ideal gas in paraffin-sealing, the enhanced cantilever beam model under water cooling, and the simply supported beam model for investigation of the cause of the water seepage. The criterion of impervious water was put forward and developed with anti-inference method. The case analysis shows that the seepage is caused by the unreasonable structure of the seal of PE pellet. On the basis of this, the seal allowance of the shell is improved and optimized in the current design. And the overlap amount of the half shells was increased from 0.15mm to 0.30mm, at least, with protruding and half shot shell with concave is increased and the small Angle of the double V structure is adopted. The results of calculation and test show that the new design is of rational and reliability, and it met the requirements of small force and ease in opening the shell.

Integrated Geophysical and Packer Test for the Water Tightness Evaluation of Gullele Botanic Garden Dam Site, Northwest of Addis Ababa, Ethiopia

Gullele Botanic Garden is one of the largest botanical gardens in Ethiopia, which is found northwest of Addis Ababa. For this garden, a dam was proposed to be constructed for irrigation and recreational purposes. The intended dam will have a height of 30 m and a dam axis length of around 180 m. The main objective of this work is to investigate and evaluate the engineering geological aspects of the proposed dam site based on detailed geological, geotechnical and geophysical investigations. The investigation conducted in the area includes, electrical resistivity imaging, VES, borehole drilling and single packer permeability test. Geologically the area is covered by the different volcanic rock such as ignimbrite, rhyolite, tuff, basalt, and residual soil; and geological structures such as joint, fracture, flow banding, and cooling joint. The dominant orientations of geological structures are N-S and E-W directions. Results from different investigations revealed that three geotechnical layers were identified. These are overburden (completely weathered ignimbrite and soil), highly to moderately weathered ignimbrite and moderately to slightly weathered ignimbrite rock mass. The rock mass permeability test from six boreholes has Lugeon values ranging from 0 to 9. The maximum Lugeon (permeability of the rock mass) values investigated at the left abutment and riverbed of the proposed dam site showed wash out and dilation behavior respectively. The permeability result indicates that possible seepage problem at left abutment, riverbed and reserviour of the proposed dam. Therefore, during the construction of the dam, those specific locations, which are identified as problematic areas, need effective ground improvement works and special monitoring.

Fully-coupled hydro-mechanical cracking using XFEM in 3D for application to complex flow in discontinuities including drainage system

The presence of uplift pressures in cracked plain concrete hydraulic structures is a major concern for their durability, serviceability and stability. To assess the performance of cracked structures several mechanical and hydraulic response parameters must be computed. This paper presents the development, implementation and application of a new nonlinear combined segregated fully-coupled hydromechanical model for application to non-planar 3D hydraulic fractures where complex flow is occurring. The eXtended Finite Element Method (XFEM) formulation is used, as it facilitates the computation of the crack aperture as well as the application of water pressure on crack surfaces for the simulation of hydraulic fracture initiation and propagation. To take into consideration the effects of drainage in numerical modeling and simulation, two coupled (multi-physics) finite element models are used; (1) one for the uplift pressures where a hydraulic mesh with refinement around drains is used, and (2) one for the mechanical response coupled with the computation of the unsaturated interstitial seepage problem. The two subproblems are solved using a partitioned procedure, as they have different resolution requirements. Finally, the mechanical mesh and the hydraulic mesh have non-matching discrete interfaces that must be coupled while respecting the equilibrium of the applied loads. Applications of the proposed hydromechanical constitutive model and numerical solution strategy to different problems are presented on a wedge splitting test and a full scale gravity dam including multiple drainage configurations. A case study adapted from a real dam is also given with a complex 3D non-planar discontinuity surface.

Cause Analysis and Structural Measures of Seepage in Basement——Take the Basement of Student Apartment in the East Campus of XXX College as an Example

According to the problem of basement seepage, the paper analyzes the reasons of seepage synthetically, selects suitable waterproof materials according to different positions, and puts forward corresponding prevention measures and specific construction methods.

Solution of seepage field in different soil layers of concrete dam foundation by flow net method

Because of the seepage problem of concrete dam foundation, the water head, pore water pressure, hydraulic gradient and seepage velocity of each point in the seepage field are obtained by drawing flow net, and finally the seepage flow is obtained to predict the seepage of dam foundation. In this paper, the flow net diagram is used to solve the pore water pressure at the fixed point of the dam foundation soil layer under three different conditions: homogeneous isotropy, homogeneous anisotropy and layered soil. The calculation accuracy of the flow net method is verified through the calculation with the finite difference software FLAC3D numerical analysis. The results indicated that the pore water pressure of the three kinds of dam foundation soil layers calculated by the flow net method is more similar from that calculated by the numerical method, which indicates that the flow net method has high accuracy and can be used in some engineering practice with difficult modeling.

A different approach to the network method: continuity equation in flow through porous media under retaining structures

PurposeThis study aims to present a new numerical model for the simulation of water flow through porous media of anisotropic character, based on the network simulation method and with the use of the free code Ngspice.Design/methodology/approachFor its design, it starts directly from the flow conservation equation, which presents several advantages in relation to the numerical simulation of the governing equation in terms of the potential head. The model provides very precise solutions of streamlines and potential patterns in all cases, with relatively small meshes and acceptable calculation times, both essential characteristics when developing a computational tool for engineering purposes. The model has been successfully verified with analytical results for non-penetrating dams in isotropic media.FindingsApplications of the model are presented for the construction of the flow nets, calculation of uplift pressures, infiltrated flow and average exit gradient in anisotropic scenarios with penetrating dams with and without sheet piles, being all this output information part of the decision process in ground engineering problems involving these retaining structures.Originality/valueThis study presents, for the first time, a numerical network model for seepage problems that is not obtained from the Laplace's governing equation, but from the water flow conservation continuity equation.

A new method for determining the hydraulic aperture of rough rock fractures using the support vector regression

Understanding fluid flow in rock fractures is relevant to many engineering applications, including underground nuclear waste disposition, oil and gas exploitation, dam and slope design, as well as contaminant transport. Rough rock fracture is usually idealized as two parallel plates separated by the hydraulic aperture, the determination of which is key to solving seepage problems in fractured rock using the cubic law. The mechanical aperture and fracture morphology are the main aspects affecting the hydraulic aperture. Here, an innovative hydraulic aperture prediction equation for two-dimensional fractures is established based on the mechanical aperture and fracture morphology. Six parameters were firstly selected to predict the hydraulic aperture, including three mechanical aperture parameters and three fracture morphology parameters. A training database was then established from numerical experiments of 300 fracture models, which were built based on Barton's 10 standard profiles and their combinations. The numerical experiments were conducted with FLUENT software. Based on the database, a hydraulic aperture prediction model was established using the support vector machine theory and the particle swarm optimization algorithm, which was transformed into an explicit equation. Finally, 20 natural fractures were used to validate the performance of this equation, with the comparisons of four existing empirical equations. The results show that this method worked well in predicting the hydraulic aperture. This method provides an alternative and effective way to directly determine the hydraulic aperture using the geometry information of rough rock fractures.

Experimental and Numerical Analysis for Earth-Fill Dam Seepage

Earth-fill dams are the most common types of dam and the most economical choice. However, they are more vulnerable to internal erosion and piping due to seepage problems that are the main causes of dam failure. In this study, the seepage through earth-fill dams was investigated using physical, mathematical, and numerical models. Results from the three methods revealed that both mathematical calculations using L. Casagrande solutions and the SEEP/W numerical model have a plotted seepage line compatible with the observed seepage line in the physical model. However, when the seepage flow intersected the downstream slope and when piping took place, the use of SEEP/W to calculate the flow rate became useless as it was unable to calculate the volume of water flow in pipes. This was revealed by the big difference in results between physical and numerical models in the first physical model, while the results were compatible in the second physical model when the seepage line stayed within the body of the dam and low compacted soil was adopted. Seepage analysis for seven different configurations of an earth-fill dam was conducted using the SEEP/W model at normal and maximum water levels to find the most appropriate configuration among them. The seven dam configurations consisted of four homogenous dams and three zoned dams. Seepage analysis revealed that if sufficient quantity of silty sand soil is available around the proposed dam location, a homogenous earth-fill dam with a medium drain length of 0.5 m thickness is the best design configuration. Otherwise, a zoned earth-fill dam with a central core and 1:0.5 Horizontal to Vertical ratio (H:V) is preferred.