Left Abutment Research Articles

Onsite Seismic Monitoring Behavior of Undamaged Dams During the 2023 Kahramanmaraş Earthquakes (M7.7 and M7.6).

On 6 February 2023, two major earthquakes struck Türkiye, with their epicenters in the Pazarcık (M7.7; focal depth: 8.6 km) and Elbistan (M7.6; focal depth: 7 km) districts of Kahramanmaraş city. Most of the dams in the earthquake region remained structurally safe and stable. However, 17 dams in Türkiye and 1 dam in Syria were damaged during the 2023 Kahramanmaraş earthquakes. The main objective of this study was to better understand the real seismic behaviors of the dams during the two mainshocks and significant aftershocks. An earthfill dam, a concrete-faced rockfill dam (CFRD), and a roller-compacted concrete (RCC) dam constructed in the disaster area were selected to identify the real seismic behaviors of different types of dams during strong earthquakes. Acceleration records measured at the crest, right and left abutments, and foundations of the selected dams during the 2023 Kahramanmaraş earthquakes were taken into account to determine the real seismic behavior of the dams before, during, and after the earthquakes. The results of this investigation provide valuable insights into the real seismic behaviors of different types of dams in the vicinity of fault lines during strong earthquakes.

Engineering geological investigation of Gololcha dam for evaluation of leakage and abutment slope stability, Eastern Ethiopia

The Ethiopian economy is primarily dependent on agriculture, making the construction of water harvesting facilities, such as dams, crucial for improving the productivity of this sector. The ongoing construction of the Gololcha dam on the Kurkura River located in Eastern Ethiopia aims to enhance irrigation schemes in the region. However, the dam site's complex geological and structural conditions pose challenges related to leakage and slope instability. Hence, this study focuses on addressing the abutment slope stability and leakage condition of this dam. This study employed kinematic analysis and the Limit Equilibrium Method (LEM) to assess slope stability. Additionally, engineering geological mapping, discontinuity surveys, seismic refraction tomography (SRT), and in-situ permeability testing were used to evaluate the leakage condition of the dam site. Notably, the permeability and SRT survey results identified potential leakage zones to the depth of 35, 30, and 35 m at the left, right, and central foundations of the dam, respectively. The kinematic method revealed one planar and two wedge modes of failure in the slope section covered by slightly weathered and fractured basalt rock at the right abutment. Further stability analysis of these two modes of failures via LEM analysis indicated slope instability under saturated conditions, emphasizing the role of pore water pressure. Furthermore, LEM modeling was directly utilized using the Slide 6.0 software to analyze the slope stability condition of the left abutment of the dam. This modeling also uncovered instability under saturated conditions. Based on the study findings, this study recommended curtain grouting to address potential leakage, as well as slope flattening and removing unstable rock wedges and loose material to stabilize unstable slope sections.

Evaluation of watertightness and slope stability analysis of Upper Guder dam, West Showa, Central Ethiopia

Ethiopia is currently emphasizing the construction of micro dams to enhance agricultural productivity and assure food security. The Upper Guder Dam, situated in the West Shoa Zone, Central Ethiopia, is one such project. However, the dam faces challenges due to complex geological and structural conditions, including leakage and slope instability. Hence, this study focuses on addressing the abutment slope stability and watertightness condition of this dam. Accordingly, the study employed discontinuity surveying, Seismic Refraction Tomography (SRT), Rock Quality Designation (RQD), and Lugeon testing to assess the water tightness. Additionally, kinematic analysis and the Limit Equilibrium Method (LEM) were used to evaluate abutment slope stability. Results from surface geological mapping and core drilling showed that the dam site is constituted by quaternary soil, tuff, and basalt. The Lugeon test results indicate that the left abutment of the dam is susceptible to leakage down to a depth of 40 m, which suggests that the permeable zone extends deeper than the results revealed by the SRT. Furthermore, this test demonstrated that the dam's right and central foundations are susceptible to leakage to the drilled depths. The SRT revealed that the central foundation, right, and left abutments of the dam are susceptible to leakage to the depth of 35 m, 30 m, and 34 m, respectively. Moreover, the kinematic analysis revealed that a section of the left abutment of the dam is susceptible to wedge mode of failure due to the intersection of JS1 and JS2. The LEM modeling of the right abutment of the dam also depicted that this section of the dam is unstable under saturated conditions which illustrates the importance of precipitation as the major slope destabilizing factor in the study area. Based on the study findings, this study recommended the use of curtain grouting to address the water tightness issue and slope angle reduction to mitigate the slope instability problem.

Assessment of engineering geology and grouting applications in Yalnızardıç Dam Site (Antalya, Türkiye)

The Yalnızardıç roller compacted concrete (RCC) dam, constructed in 2015, is located in the Mediterranean region of Turkey, intended for electric power production. It is approximately 303 m long and 92 m in height. In this paper, it is aimed to determine the performance of the grouting method, conducted to control the water seepage and improve the foundation of the Yalnızardıç dam. The engineering properties of the site were introduced by geological mapping, drilling, and laboratory tests. The seepage of the foundation was determined by the in-situ Lugeon test method, also referred to as a water pressure test, which is estimate the mean hydraulic conductivity of rock mass. As a result of the tests, high-permeable and permeable zones were determined in the dam axis area. To make a barrier layer for these permeable zones, grout curtains were built in the left abutment, thalweg and right abutment with two lines of grouting holes which is proposed according to the Lugeon test and rock quality designation (RQD) results. Consolidation grouts were built to increase the density of the soil which makes the strength of the dam's foundation. After the groutings, check boreholes were drilled and water pressure tests were performed to control the seepage along the foundation and dam site. The results indicated that average Lugeon (LU) values reduced, and the values were within the recommended limit. The process shows considerable accuracy in evaluating grouting efficiency.

An Engineering Geological Appraisal of the Leakage Problem in Dora-1 Earthen Dam, Tigray: Implications for its Stability

Leakage is one of the major problems facing the functionality and sustainability of dams. It occurs through the embankment body, reservoir, foundation, and abutments. This study was conducted to identify the main causes of the leakage problem at the Dora-1 dam, located in the northern part of Ethiopia. It is an earthfill dam with a height of 43.5 m, crest length of 454 m, and reservoir capacity of 4.67 million cubic meters. Part of the embankment body was wet and swampy up to 20 m high from the ground due to leaking water. Geological investigation, laboratory test of the construction materials (including grain size analysis, specific gravity and water absorption, Atterberg limit, free swell, dispersion, permeability, and shear strength), and electrical resistivity investigation were used to identify and pinpoint the possible causes of the leakage problem. Results of the study show that the favorable geological features responsible for the occurrence of leakage include: (a) geological contact between sandstone and moderately to highly weathered basalt unit at the left abutment, (b) the gravelly sand deposit at the central foundation and (c) dyke outcrop at the river course within the reservoir running in the upstream-downstream direction. Results of laboratory tests for clay core show medium to high compressibility, good to poor workability, and semi-pervious to impervious permeability when compacted. The water absorption and the percentage finer of the filter material don’t satisfy the filter criteria and the shell material was found to be semi-previous. The anomalous in the resistivity survey result confirms the situation. Slope stability analysis of the embankment showed instability conditions at full reservoir level. Close follow-up and a downstream stabilization structure, including rock and gravel support, were recommended.
 Construction material; Embankment dam; Site investigations; Ethiopia.

Investigating the geomechanical properties and permeability of the rocks of the Kurit dam site using geostatistical methods

As dams play a very important role in the optimum use of water resources, it is very important to keep them stable and the water stored in the reservoir. It is particularly important to investigate how water moves through rocks and the permeability and quality of the rock mass in structures like dams. Therefore, one of the issues considered in dam stability is monitoring the quantity of leaks. In this research, the engineering geological and geotechnical parameters of the rock mass for the construction of the Kurit Dam located in the city of Tabas in eastern Iran were evaluated. Initially, following the determination of geotechnical parameters, the engineering classification of the rock mass of the study area was carried out. In addition, in order to study and trace the water evacuation routes of the dam construction, two parameters of the RQD and Lugeon were studied and modelled. Analyses have been conducted to examine the permeability and rock quality index in three parts of the left and right abutment, the dam’s axis and reservoir with geostatistics and kriging methods. Three-dimensional model of the construction of the Kurit dam was presented and the results were analyzed. Based on the results, the quality of the rock mass in the right and left abutments is arguably better than the dam axis and reservoir. Additionally, as the depth increases, the permeability decreases and the permeability is higher at shallow depths. The highest level of permeability is located at the surface and near the BH4 borehole.

Integrated Geophysical and Geotechnical Approaches for Evaluating Dam Seepage in Lesser Himalayan Region of Pakistan

Dam leakage is a major problem in earth-filled reservoir dams. The present research is aimed at detecting the seepage zones in an earth-filled reservoir dam in the vicinity of Sarobi village, North Waziristan, Pakistan. The objective was achieved by integrating geological, geotechnical, and geophysical datasets. Geological survey was carried out in the area to identify the surface exposures. Geotechnical data involved was used to estimation of permeability and Lugeon values to identify network of joints/fractures whereas electrical resistivity tomography (ERT) technique (utilizing Wenner-Schlumberger configuration) was applied for the identification of the leakage zones. Geological data revealed highly deformed alluvium towards the right abutment underlain by compressed shale and highly fractured limestone beds. Geotechnical data indicated high permeability, Lugeon values, and concentration of sand and gravel towards the right abutment whereas low permeability, Lugeon values, and higher concentration of silt and clay were observed towards the left abutment. ERT data identified a conductive zone embedded between impermeable lithologies having resistivity between 10 and 60 Ω·m. This conductive zone was observed in parallel profiles acquired in upstream, dam crest, and downstream parts of the dam. The integration of all the datasets revealed a network of joints that are interconnected and provide a path for water at the upstream side to pass through right abutment of dam and leak towards the downstream.

THE EMERGENCE AND DEVELOPMENT OF A CRACK IN THE CONCRETE OF THE ABUTMENT OF THE LOWER HEAD OF LOCK № 2 OF THE VOLGA-BALTIC WATERWAY

An analysis of the concrete structures state of the lower head of lock № 2 of the Belousovsky hydroelectric complex of the Volga-Baltic waterway is presented. In 1985, a crack was discovered in the concrete of the left abutment of the lock lower head. Observations for the dynamics of its development have showed that the crack size increases with time. To explain the causes of the crack occurrence and development, an analysis of concrete quality of the lower head structures is made according to the data of previous studies. Taking into account the technology of concreting during the construction process, as well as studies carried out during operation, the low quality of concrete and its heterogeneous structure have been stated. The analysis of the soils structure at the base of the lower head is carried out; the filtration regime of groundwater movement is considered. It is noted that the base soils are represented by fine-grained sands with an interlayer of loams. The presence of several aquifers in the basement soils, as well as the formation of the pressure front of the hydroelectric complex, led to significant gradients of the filtration flow. This contributed to the development of suffusion processes in the soils of the lower head base, which led to the formation of a decompacted layer in the roof of the rocks of the lower head base. The data of modern surveys of soil characteristics confirm that suffusion processes continue at the present time. This led to the occurrence of multidirectional settlement of the right and left abutments of the lower head, which, in turn, led to the development of the crack in the concrete mass. The measures taken to eliminate or stabilize the development of the crack, namely, pumping a cement-sand mixture into the soil, grouting the abutment concrete, anchoring the structure, injecting the concrete mass with a two-component synthetic resin, have not stopped the crack opening, because the main reasons such as the poor quality of concrete and the weak bearing capacity of the underlying soils of the base had not been eliminated.

Pore-water pressure accumulation during closely spaced earthquakes: Fundão Tailings Dam

ABSTRACT This paper focuses on pore-water pressure accumulation in loose sandy tailings during three (3) earthquakes within four minutes and the accompanying decrease in effective stress to assess the dynamic stability of the Fundão Tailings Dam, which failed on 5 November 2015. Results of laboratory cyclic direct simple shear tests are used to illustrate the accumulation of pore-water pressures with closely spaced low-level cyclic events. The seismically-induced pore-water pressures in the loose sands below the left abutment downstream slope and setback area are used to estimate the decrease in factor of safety with time until failure occurred within 20–30 minutes of the earthquakes. Field cone penetration and standard penetration test conducted prior to the failure are used to calculate the factor of safety against liquefaction to estimate pore-water pressures generated during the fore, main, and aftershocks in the sandy tailings. The effective stress stability analyses utilise a liquefied shear strength ratio for the sand tailings below the left abutment downstream slope and toe of the plateau because the sand tailings reached the critical state condition due to a reduction in the effective stress. SITE LOCATION: 20.206500°S, 43.467111°W

Rough River Dam Safety Modification Project Evolution

Abstract This paper is a case study documenting how the Rough River Dam Safety Modification Project evolved over time. Rough River Dam is an embankment dam located in west-central Kentucky that is owned and operated by the U.S. Army Corps of Engineers (USACE) for flood risk management. The project has a right abutment cut-and-cover outlet conduit founded upon karstic limestone. In 2012, a Dam Safety Modification Report (DSMR) was completed that identified multiple internal erosion-related potential failure modes requiring mitigation. The DSMR recommended a multi-phased approach. The Phase I project included construction of a work platform in order to perform exploratory drilling and grouting for two partial grout lines. The Phase II project was to consist of grout line completion, construction of a full-length cutoff wall over and around the existing outlet conduit, grouting within the outlet conduit, and construction of a downstream filter. Based on encountered conditions, the Phase I grouting contract was modified to complete both partial grout lines for slurry control prior to cutoff wall construction. During design of the Phase II cutoff wall, the existing outlet conduit was determined to be structurally inadequate to support the cutoff wall. A Supplemental DSMR recommended a new left abutment outlet works to permit the existing conduit to be severed and to allow for construction of the full cutoff wall across the dam foundation. The Phase II design was completed in the fall of 2021. This paper summarizes the key information, findings, and decisions that informed the final direction of the project.

Deformation Mechanism and Crack Cause Analysis of the Left Abutment Slope of Yangfanggou Hydropower Station

The geological conditions of the left abutment slope of Yangfanggou Hydropower Station are complex, and the unloading effect in the rock mass developing with slope-oriented steep-gentle-dipped fractures is strong. During the excavation of slope, the deformation and cracking response in rock mass on the upstream side of the arch dam foundation have been found successively, the stability of slope and personnel safety has been significantly influenced. Based on engineering geological survey and monitoring data analysis, a discrete element simulation model is built for deformation mechanism and crack cause analysis of the left abutment slope. The calculation results show that: the fault f27 and slope-oriented structural plane with gentle dip are the main factors that influence the deformation response during excavating the slope. During the excavation of the slope above E.L.2000m, f27 has an obvious influence on the local stress at the foot of the slope. The stress will be concentrated in the upper part of f27 firstly and then unloading and relaxed under the combined action of the slope-oriented structural plane. The shear deformation happens along with the fault f27, and the subsidence of its hanging wall caused the crack of the rock mass. The slope stability will be significantly reduced with f27 exposed on the excavation face, there is a large risk of slip and instability. Pre-stressed anchor cables are used to stablish the foot and strengthen the slope half, which can effectively improve the stability of the slope and control the shear deformation of f27. After the pre-stressed anchor cables are applied, the safety factor of the slope is increased from 0.98 to 1.20, and the monitoring data show that the deformation is controlled successfully.

Ground displacements revealed by A-DInSAR analysis in the Germano iron mining complex before and after the Fundão Dam collapse using Sentinel-1 data

Advanced differential SAR interferometry (A-DInSAR) has been used as an effective monitoring tool in mining environments. This work presents an investigation of surface displacement in the Germano iron mining complex (Mariana, Minas Gerais, Brazil), where on November 5, 2015, the Fundão tailings dam collapsed. Initially, the analysis was performed with 14 Sentinel-1 images, acquired from May 8, 2015, to November 4, 2015, and focused on the Fundão dam before its rupture to detect prior signs of surface deformations. The analysis after the Fundão dam collapse was conducted in the Germano area using 43 Sentinel-1 images, acquired from November 16, 2015 to May 15, 2017, and aimed at detecting surface displacement on the remaining infrastructure, the Sela&Tulipa and Selinha dikes and the main Germano tailings dam, which were directly or indirectly affected by the accident. The results reveal precursor signals of surface displacement at the Fundão dam prior to rupture, particularly on the left abutment setback sector where the collapse started according to a witness, reaching accumulated values of up to −60 mm. The results provided by the A-DInSAR analysis after the dam collapse indicate a stability in the Sela&Tulipa and Selinha dikes as well as in the main Germano dam, which is corroborated by in situ topographic measurements. On the auxiliary dikes within the Germano reservoir, accumulated displacement of up to −90 mm caused by settlements and continuous traffic of vehicles was detected. In addition, the detected accumulate displacement within the reservoir showed values of up to −120 mm, in general caused by settlements of the waste dry material due to the inactivity of the mining process. The investigation emphasized the important role that satellite-based A-DInSAR can play in mitigating possible accidents and for operational planning and risk assessment in mining operations.

Hydrologic and hydraulic assessment of scour problems at bridge sites in Tigray region, northern Ethiopia

This study was conducted to assess scour problems at three selected bridge sites in the Tigray region, northern Ethiopia, namely the Ilala, upper Geba, and Tankwa bridges. Smart-GIS, ArcGIS, Hydrologic Engineering Centre Hydrologic Modeling System (HEC-HMS), and Hydrologic Engineering Centre River Analysis System (HEC-RAS) were used for the river morphology, hydrologic, and hydraulic analysis. The riverbanks were subjected to higher degradation and instability problems. The estimated 100-year flows were 272.5, 940.4, and 249.9 m3/s for Ilala, upper Geba, and Tankwa bridges, respectively. Flow depth calibration were resulted in model performance with Nash Sutcliffe Efficiencies of 0.90, 0.88, and 0.87 for Ilala, upper Geba, and Tankwa bridge sites, respectively. Scour depths were 1.3, 1.6, and 0.8 m at contracted sections; 3.2, 3.0, and 2.2 m at the piers; 2.6, 3.6, and 2.2 m at the left abutment; and 1.6, 3.0, and 2.1 m at the right abutment of Ilala, upper Geba, and Tankwa bridges, respectively. The use of riprap at the bridges resulted in the reduction of scour depths by 60–100%. Overall, the hydrologic and hydraulic models performed well.

Accuracy of the Provisional Prosthesis Scanning Techniqueversus a Conventional Impression Technique on Completely Edentulous Arches

Purpose: In this study, we aimed to compare the marginal fit of fixed dental restorations fabricated with the provisional prosthesis scanning technique versus a conventional impression technique and to determine the effect of both variables on the accuracy outcome. Materials and Methods: Twelve identical polyurethane edentulous maxillary models were equally divided into two groups: control (conventional impression group) and test (provisional prosthesis scanning group). After obtaining the impression using the above-mentioned methods and further preparing the final prosthesis, the passivity of the metal framework prosthesis was checked using a single screw test, i.e., only one screw was fixed on the terminal right abutment, and all others were empty. The marginal fit of the final prosthetic frameworks screwed onto the implants on the terminal left abutment was measured at the terminal right sight by periapical radiographs obtained immediately after metal framework placements in both groups. The medians derived from the two groups were compared using the Mann–Whitney test. In all tests, a p-value < 0.05 indicated statistical significance. Results: In the provisional prosthesis scanning group, the median marginal fit discrepancy was 170 µm (range 120–190). In the conventional impression group, the median marginal fit discrepancy was 1080 µm (range 1040–1100). There was a significant difference in the implant-framework marginal gap fit discrepancy between these two groups. Conclusion: Prostheses fabricated with the provisional prosthesis scanning technique are significantly more accurate than those fabricated with conventional impression techniques.

Reservoir bank slope stability prediction model based on BP neural network

Safety monitoring and stability analysis of high slopes are essential for construction of concrete dam in precipitous gorges or mountainous areas. The estimate of slope stability is a difficult engineering shortcoming with a number of variables. Thereafter, a hybrid model of Support Vector Regression (SVR) and Teaching–learning-based optimization technique (TLBO) is proposed to develop the predicting function. TLBO was used in obtaining the best SRV factors to improve the prediction accuracy. Few essential factors, such as the installation height of instruments, classification of rock masses, modulus of elasticity, the complete measuring time cycle, the excavation height of slope, the start measuring time, and the actual excavation height after measurement are considered as the input parameter, but the slope displacement is regarded as output. The outcomes showed SRV-TLBO a reliable hybrid accurate prediction of slope stability, then it was effectively used to the left abutment slope of Jinping I hydropower station located in Yalongjiang concrete dam reservoir as a novel method for this purpose.

Application of Micro Earth Pressure Cells to Geomechanical Model Tests of Arch Dams

Geomechanical model tests are important in the evaluation of the stability of engineering rock masses, and they play a key role in the stability studies on arch dam abutments. To further analyze the instability failure process and mechanical characteristics of dam abutment rock masses, this study employed a stress monitoring system in the traditional strain and displacement monitoring to improve the comprehensiveness of test results. With their advantageous properties, including their small volume, high sensitivity, and strong stability, micro earth pressure cells can directly monitor stress changes in arch abutment rock mass during geochemical model tests. On the basis of the overloading method, this study applied micro earth pressure cells to a 2D geomechanical model test on the Yebatan arch dam to investigate the working performance of the arch dam and arch abutment at EL.2 750 m. In the test, the surface displacement monitoring system and micro earth pressure cells on both sides of the deep unloading belts of the left and right dam abutments were arranged to study the pressure changes at the arch abutment and the influence of the geological structure. The results showed that the measured stress value near the arch abutment was large and that the measured stress value greatly decreased after passing through the deep unloading belt. Class IVs of strongly relaxed rock masses in the left abutment exerted an obvious attenuation effect on the arch thrust while fault f29 (f74) greatly influenced the right abutment. The results were verified by the displacement test data. The application of micro earth pressure cells facilitated the direct observation and analysis of dam abutment stress and improved the completeness of the test results. Thus, the proposed approach provides a new idea for geomechanical model tests.

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.

Assessing the Efficiency of Seepage Control Measures in Earthfill Dams

Seepage control in earthfill dams is a major concern during different phases of dam construction and operation. More than 30% of earthfill dam failures occur due to uncontrolled flow in the dam body and foundation. Seepage control measures, designed and installed at suspected sites of uncontrolled flow, thus play a vital role in stabilizing earthfill dams. However, the actual efficiency of seepage control measures often falls short of expected performance due to soil heterogeneity and changes over time. Assessing the performance of seepage control measures based on monitoring and modeling is necessary to avoid abrupt failures in earthfill dams. In this study, we developed a novel method for quantifying the efficiency of seepage control measures in earthfill dams based on combined seepage modeling and monitoring data. We tested the method by applying it to assess the efficiency of seepage control components at the Doroudzan dam, Iran. The results revealed that the overall efficiency of the dam’s seepage control measures (depending on water level in the reservoir) was 51–70%, based on the magnitude of discharged flow. The efficiency of three major seepage control devices, the chimney drain, cutoff wall, and grouting diaphragm in the left abutment, was 76–82%, 68–74%, and 16–19%, respectively.

Investigation into the Internal Erosion and Local Settlement of Esfarayen Earth-Fill Dam

AbstractA considerable sudden settlement was discovered on the Esfarayen Earth-fill Dam surface near to the left abutment when the reservoir level rose to 51 m from the riverbed in April 2013. As a...

Experimental Study on the Global Stability of the xiaowan Arch Dam Using a 3D Geo-mechanical Model Test

In this paper, a three-dimensional geo-mechanical model test for the Xiaowan high arch dam was studied and the topographical and geological features, the distribution of weak structural planes, the shallow relaxation unloading phenomena were simulated. Furthermore, a type of model material known as the temperature analogous material, whose strength varies with temperature throughout the experiment, was used to simulate the decrease in shear strength of the weak structural planes. The deformation characteristics and failure mechanism of the dam foundation and abutments were obtained by using comprehensive test method, which considered both the overloading and strength-reduction techniques. Through data analysis, the strength reserve coefficient, the overloading and the global safety factor were obtained. Synthetic analysis of the test results indicates that the displacement of the mid-upper abutment was reduced and the failure zone become smaller due to the significant reinforcement effects of concrete displacement plugs on the faults and alteration zones. The failure pattern shown in the model test indicates that reinforcements should be installed at faults F11 and F10 above an elevation of 1245 m in the right abutment and the rock above the thrust block in the left abutment.