Engineering Geological Conditions Research Articles

GEOTECHNICAL CONDITIONS FOR THE WIDENING OF THE EXISTING EMBANKMENTS ON THE GOLUBOVCI-BAR RAILWAY SECTION, THE SECTION THROUGH SKADAR LAKE

The reconstruction of the existing embankments along the Golubovci-Bar railway line, particularly through the section that traverses Lake Skadar, represents a significant engineering challenge due to the location's specific characteristics and ecological restrictions. This area is a protected region, which limited the implementation of certain design solutions. Embankment stability analysis using the finite element methodndicated that the existing embankment does not meet the global safety factor requirements for design earthquake according to Eurocode 8. The paper presents the engineering-geological conditions of the existing embankments, as well as recommendations for their expansion and stabilization.

Failure mechanism of loess landslide induced by water stagnation on the combined surface

In order to reveal the destructive mechanism of loess landslide induced by stagnant water on the combined surface, and to clarify the influence of the main control factors, this paper takes a typical loess landslide in northern Shaanxi as the research object, analyzes the structure of the rock and soil body, and the excavation and filling construction through the geohazard survey, and analyzes the process of traction sliding caused by the stagnant water on the combined surface at the different stages of the project by combining with the calculation of the stability of the slope body. Further the article analyses the process of traction sliding caused by water on the combined area due to construction by means of a discrete element model, and delves into the mechanism of strength reduction of saturated loess. The results show that: 1) the combined surface stagnant water type loess landslide has the characteristics of sudden sliding and rapid evolution, which is highly hazardous and difficult to prevent and control; 2) the slope destabilization is controlled by the engineering geological conditions, and the slope excavation changes the original mechanical equilibrium conditions of the slope, which provides the dynamic conditions for the traction sliding of the slope; 3) the change of the hydrogeological environment results in the obstruction of the natural drainage channel, which leads to the formation of continuous sliding surface due to stagnant water on the combined surface, and the formation of a continuous sliding surface due to stagnant water on the combined surface. Surface stagnant water to form a continuous slippery surface, inducing the overall destabilization of the slope damage; 4) loess strength index with the increase of saturation and the exponential function form of reduction, and when the saturation degree reaches more than 80%, the strength index of the soil body to reach the basic stability. The article expanding the ideas of landslide control and analysis, and the research results will provide a theoretical basis for the design of junction landslide management in the loess areas of northern Shaanxi.

Based on Flac3D Research and Analysis of the Mining Pressure Development Law in the Top Coal Section of the Roadway Support of the Working Face Transport

Top coal supporting roadway is widely used in the transportation roadway of thick coal seam face, which can not only increase the coal extraction rate but also reduce the driving cost. Based on the engineering geological conditions of the transportation lane of the working face of Zhongma Cun mine, the law of mine pressure development in the roadway of the top coal section is studied and analyzed based on Flac3D and field monitoring methods. The numerical simulation analysis shows that when the working face is pushed to 55m for the first time, the displacement of the area affected by the leading abutment pressure and the surrounding rock on the mining side of the roadway reaches the peak value, and the step distance of the first time is 55m. According to the analysis of stress monitoring data of single pillar and roof anchor cable on site, the first pressure occurs when the working face advances to 51m, which is consistent with the numerical simulation conclusion.

Engineering-geological conditions of the Shirvan Steppe of the Kura-Aras Lowland of Azerbaijan Republic and the influence of the Upper-Shirvan Canal on it

Since 1950, the area of the Shirvan Steppe has been subject to numerous ameliora- tive measures, as well as the construction of a number of hydrotechnical facilities. Natural and anthropogenic effects have altered the level of groundwater, mineralization level, chemical composition, engineering-geological conditions, soil salinity, and chemical composition of soils. In order to reflect the engineering-geological conditions of the Shirvan Steppe, geological-hydrochemical sections were created in two directions, in the direction of groundwater flow (I-I) and the direction across the flow of groundwater (II-II). The analysis consid- ered the engineering-geological, physical-geographical, geomorphological, geological, and other conditions of the studied area before and after construction of the Upper Shirvan Canal. Along the route of the Upper Shirvan Canal, the research revealed the main soils as follows: loam, clay, gravel-pebble, sand, and loamy sand. The engineering-geological parameters such as minimum moisture capacity, hygroscopic moisture, volume, weight, density, porosity, and granulometric composition of the soils along the route of Ujar, Kurdamir, Goychay regions, and the Upper Shirvan Canal have been determined. Over the 70-year continuous operation of the Upper Shirvan Canal, settlements in the area of its influence expanded, thereby increasing the loading on the canal beyond the norm. As a result of damage to the concrete coatings of the canal, the quality of operation has decreased, some infrastructure located on it has ceased to function, and water losses from the canal have increased. In such conditions, it is important to study the formation of engineering-geological conditions resulting from natural and anthropogenic effects and to take preventive measures against negative impacts. During the reconstruction and subsequent operation of the canal to provide water to the newly irrigated land areas in the Shirvan Steppe, there should be taken into account the technogenic effects on the geological environment and relevant proposals of important scientific and practical importance regarding the reconstruction project.

Determining the Stability of a Potentially Dangerous Landslide Slope

Abstract Due to the acceleration of construction of civil, industrial and infrastructure facilities in our republic and the expansion of their area, the construction of many facilities is carried out in mountainous, and foothill areas with complex relief and geomorphological conditions, which in most cases are potentially dangerous landslide slopes. To protect these facilities from the negative impact of dangerous geological, natural-technogenic, and anthropogenic processes, to assess the risks arising from the impact of these processes on building structures, to promptly prevent negative phenomena and dangerous situations, to assess the engineering and geological conditions of the construction area to determine the stability of the slope, conducting research in these areas is of great practical importance. Mountainous regions are characterized by the complexity and diversity of geological, hydrological, hydrogeological, and tectonic conditions. Landslides are the most common natural and man-made processes that pose a threat to the safe operation of infrastructure facilities, civil and industrial construction in mountainous and foothill areas. In addition to infrastructure facilities, landslides can destroy vegetation, destroy the habitat of fauna, and also destroy fertile soils located in the area of their activity (Nikolic, 2015; Krivoguz & Bespalova, 2020). The main objective of this article is to apply the results of practically implemented and verified studies in other territories of our republic with similar geomorphological structure and engineering-geological conditions, to correctly assess the negative manifestations caused by landslides and other man-made and anthropogenic impacts, as well as to calculate the stability of the slope and scientifically and technically substantiate measures for engineering protection against landslides.

Study on the structure and strata behavior regularity of repeated mining overburden of close-distance shallow buried coal seam group

This paper studies the collapse structure, plastic failure regularity, and overburden movement regularity in the mining process of the Shallowly Buried Coal Seam (SBCS) group in the Yulin area using physical similar material simulation, computer numerical simulation, and theoretical analysis. The objective of the present article is to explore the strata behavior regularity of the SBCS group, taking the engineering geological conditions of Hongliulin Coal Mine as the sample. According to the results, when the lower coal seam of the SBCS group is mined, the initial stress step increases, and the periodic stress step decreases compared to the upper first coal seam. During the mining of the lower coal seam, there is an extreme collapse span in the interlayer rock formation: the process induces the activation of the collapsed roof in the goaf of the upper coal seam, and the overall sinking phenomenon occurs. The dynamic stress is obvious. The roof stress is significant in passing through the upper coal seam's residual coal pillar (CP) into the lower coal seam. The CP is at a certain distance, and the residual CP is violently unstable and sinks the strata behavior regularity. The interlayer rock layer forms an inclined shear staggered fracture zone along the coal wall. The research results provide a theoretical method for controlling mine stress and green and safe mining in the SBCS group of coal production enterprises.

Study of the static response and zoning of the existing tunnel adjacent to the suspension bridge's tunnel-type anchorage

Due to the ability to utilize the strength of the surrounding rock to enhance bearing capacity, tunnel-type anchorages have been consistently utilized in suspension bridges. Nevertheless, a close interaction occurs between the tunnel and the tunnel-type anchor when a highway tunnel is connected to a suspension bridge. This study employed numerical simulation and theoretical analysis based on the G317 Line Huangjiayuan tunnel and Zipingpu Bridge tunnel-type anchorage project, focusing on this specific type of adjacent engineering. Firstly, the discriminant degree of adjacent influence suitable for the interaction between the tunnel-type anchorage and the tunnel structure is established. The calculation conditions are distinguished by the influencing factors determined in the discriminant. The interaction law between tunnel-type anchorage and pre-built tunnel structure is further obtained. Using the method of curve regression, based on the criterion of proximity influence degree, the partition of mutual influence degree between the tunnel-type anchorage and the tunnel structure is obtained. At the same time, it is concluded that under the original design condition, the displacement degree of the tunnel structure will be greatly affected, and the tunnel structure is located in the strong influence area. According to the partition result, under the benchmark engineering geological condition, it is suggested that the angle of intersection between tunnel anchorage and tunnel structure should be increased to 3.3° and the anchor body inclination should be increased to 44°.

Research on prediction method of coal mining surface subsidence based on MMF optimization model

Coal seam mining causes fracture and movement of overlying strata in goaf, and endangers the safety of surface structures and underground pipelines. Based on the engineering geological conditions of 22,122 working face in Cuncaota No.2 Coal Mine of China Shenhua Shendong Coal Group Co., Ltd. a similar material model test of mining overburden rock was carried out. The subsidence of overburden rock was obtained through the full-section strain data of distributed optical fiber technology, and the characteristics of mining surface subsidence were studied. The Weibull model was used to adjust the mathematical form of the first half of the surface subsidence curve via the MMF function. On this basis, the prediction model of coal seam mining surface subsidence was established, and the parameters of the prediction model of surface subsidence were determined. The test results show that with the advancement of coal seam mining, the fit goodness of the surface subsidence prediction curve based on the MMF optimization model reaches 0.987. Compared with the measured values, the relative error of the surface subsidence prediction model is reduced to less than 10%. The model displays good prediction accuracy. The time required for settlement stability in the prediction model is positively correlated with parameter a and negatively correlated with parameter b. The research results can be further extended to the prediction of overburden “three zones” subsidence, and provide a scientific basis for the evaluation of surface subsidence compression potential in coal mine goaf.

Application of Wave Methods for Determining Comprehensive Soil Model Parameters

Comprehensive hardening soil models are widely used in geotechnical design. Some of the stiffness parameters of such models, characterizing the behavior under very small and small strains, should be determined by wave (dynamic) methods. These techniques can be implemented both in the laboratory and in the field scale. Each of the methods has its advantages and disadvantages, which directly affect the quality of the initial data obtained for calculations and the results of geotechnical forecasts and the reliability of construction facilities. The article provides an overview of wave methods applicable for stiffness parameters of complex soil models estimation. The scope of application of test methods is given depending on the geotechnical task, the defined parameters and engineering-geological conditions. The comparison of the test results by field and laboratory methods at the experimental site is given. It is shown that the results obtained by field methods require additional reference to the initial stress state in the soil mass before their application as input parameters of comprehensive soil models. Recommendations are given for correcting the initial soil shear modulus based on the integration of laboratory and field wave methods.

Novel multifractal-based classification model for the quality grades of surrounding rock within tunnels

Understanding the variation patterns of tunnel boring machine (TBM) operational parameters is crucial for assessing engineering geological conditions and quality grades of surrounding rock within tunnels. Studying the multifractal characteristics of the TBM operational parameters can help identify the patterns, but the relevant research has not yet been explored. This paper proposed a novel classification model for quality grades of surrounding rock in TBM tunnels based on multifractal analysis theory. Initially, the statistical characteristics of eight TBM cycle data with different grades of surrounding rock were explored. Subsequently, the method of calculating and analyzing the multifractal characteristic parameters of the TBM operational data was deduced and summarized. The research results showed that the TBM operational parameters of cutterhead torque, total thrust, advance rate, and cutterhead rotation speed have significant multifractal characteristics. Its multifractal dimension, midpoint slope of the generalized fractal spectrum, and singularity strength range can be used to evaluate the surrounding rock grades of the tunnel. Finally, a novel classification model for the tunnel surrounding rocks based on the multifractal characteristic parameters was proposed using the multiple linear regression method, and the model was verified through four TBM cycle data containing different surrounding rock grades. The results showed that the proposed multifractal-based classification model for tunnel surrounding rocks has high accuracy and applicability. This study not only achieves multifractal feature representation and surrounding rock classification for TBM operational parameters but also holds the potential for adaptive adjustment of TBM operational parameters and automated tunneling applications.

OPTIONS SELECTION AND IMPACT STUDY OF INTERCITY RAILWAY TUNNEL CONSTRUCTION UNDER AIRPORT INTERZONE

The selection of tunnel construction program for intercity railroad tunnel under the airport must consider the limitations of environmental conditions and the scale of tunnel construction, and the impact of construction on the airport must be controlled within safe limits. Combined with the intercity rail transit tunnel project through the airport area surrounding environment and engineering geological conditions, the use of theoretical analysis, numerical simulation and other methods, comprehensive navigation, technology, construction period, cost, construction impacts and other aspects of the comparative analysis of the tunnel construction method of open excavation method and shield method, the results show that: (1) Due to the soft soil and groundwater in the tunnel excavation area, the risk of open excavation is greater, while the shield method is more suitable for longer silty soil tunnels without affecting the navigation, accordingly, the shield tunnel construction is more suitable for the tunnel construction under the airport. (2) Open excavation method has the shortest construction period to meet the requirements of rail transit, the unit cost is between 1 and 2 shield machines, and the total cost is close to 2 shield machines; for lower total cost, choose 1 shield machine, for shortening the construction period, choose 2 shield machines. (3) The maximum ground settlement caused by shield tunneling construction is 20mm, the maximum vertical differential settlement perpendicular to the tunnel is 2.8cm, and the maximum differential settlement is 0.93 ‰. On the one hand, it meets the requirements of airport settlement control, and on the other hand, it has little impact on the vertical connecting road and west station apron, and will not affect the opening of the airport runway and the operation of the terminal.

The Influence of Metro Tunnel Construction Parameters on the Settlement of Surrounding Buildings

The construction of tunnels in conditions of dense urban development affects buildings, structures, and engineering communications located at the surface. In this work, through dispersion analysis, factors influencing the settlement of the earth’s surface and buildings during tunneling were selected. Subsequently, a model based on statistically significant parameters that can predict deformations at the pre-design stage was created. This research was conducted using data from geotechnical monitoring obtained during the construction of underground structures, with information about the technological parameters of shield tunneling in the construction of the single-track lines of the Moscow Metro using TBM with face-support pressure and engineering–geological conditions. In the obtained model, there is a clear dependency between the additional displacement of the monitoring object located above the projected tunnel and the average face-support pressure causing the mentioned deformations. The response is also affected by the soil deformation model at the tunnel face, the depth of the tunnel, and the soil excavation for the installation of one ring.

Finite–Discrete Element Method Simulation Study on Development of Water-Conducting Fractures in Fault-Bearing Roof under Repeated Mining of Extra-Thick Coal Seams

The formation of water-conducting fractures in overlying strata caused by underground coal mining not only leads to roof water inrush disasters, but also water-conducting fractures penetrate the aquifer, resulting in the occurrence of a mine-water-inrush disaster and the loss of water resources. It destroys the sustainability of surface water and underground aquifers. This phenomenon is particularly significant in extra-thick coal seams and fault-bearing areas. Numerical simulation is an effective method to predict the failure range of mining overburden rock with low cost and high efficiency. The key to its accuracy lies in a reasonable constitutive model and simulation program. In this study, considering that the three parts of penetrating cracks, non-penetrating cracks, and intact rock blocks are often formed after rock failure, the contact state criterion and shear friction relationship of discrete rock blocks and the mixed fracture displacement–damage–load relationship are established, respectively. Combined with the Mohr–Coulomb criterion, the constitutive model of mining rock mass deformation–discrete block motion and interaction is formed. On this basis, according to the engineering geological conditions of Yushupo Coal Mine, a numerical model for the development of water-conducting cracks in the roof with faults under repeated mining of extra-thick coal seams is established. The results show the following: The constitutive relation of the continuous deformation–discrete block interaction of overlying strata and the corresponding finite element–discrete element FDEM numerical program and VUSDFLD multi-coal seam continuous mining subroutine can numerically realize the formation process of faults and water flowing fractures in overlying strata under continuous mining of extra-thick multi-coal seams. The toughness of sand mudstone is low, and the fracture will be further developed under the repeated disturbance of multi-thick coal seam mining. Finally, it is stabilized at 216–226 m, and the ratio of fracture height to mining thickness is 14.1. When the working face advances to the fault, the stress concentration occurs in the fault and its overlying rock, which leads to the local fracture of the roof rock mass and the formation of cracks. The fault group makes this phenomenon more obvious. The results have been preliminarily applied and tested in Ningwu mining area, which provides theoretical support for further development of roof water disaster control under the condition of an extra-thick coal seam and avoids the loss of water resources in surface water and underground aquifers.

Rainfall-Triggered Landslides and Numerical Modeling of Subsequent Debris Flows at Kalli Village of Suntar Formation in the Lesser Himalayas in Nepal

Hazardous debris flows are common in the tectonically active young Himalayas. The present study is focused on the recurrent, almost seasonal, landslides and debris flows initiated from Kalli village in Achham District of Nepal, located in the Lesser Himalayas. Such geological hazards pose a significant threat to the neighboring communities. The field survey reveals vulnerable engineering geological conditions and adverse environmental factors in the study area. It is found that a typical complete debris transport process may consist of two stages depending on the rainfall intensity. In the first stage, debris flows mobilized from a landslide have low mobility and their runout distance is quite modest; in the second stage, with an increase in water content they are able to travel a longer distance. Numerical simulations based on a multi-phase flow model are conducted to analyze the characteristics of the debris flows in motion, including the debris deposition profiles and runout distances in both stages. Overall, the numerical results are reasonably consistent with relevant field observations. Future debris flows may likely occur again in this area due to the presence of large soil blocks separated by tension cracks, rampant in the field; numerical simulations predict that these potential debris flows may exhibit similar characteristics to past events.

Hydrogeological Investigation of a Goaf and Subsidence Area Based on a Ground-to-Air Transient Electromagnetic Sounding Method

Water hazards in coal mines have always been the main geological hazard that restricts the safety of coal mine production. The traditional electromagnetic method is difficult to accurately detect the hydrogeological conditions of underground goafs due to accuracy and interference problems. The ground-to-air transient electromagnetic method is an electromagnetic detection technology with strong adaptability to various terrains, a large detection depth, a wide coverage, a high resolution, and fast speed. This paper mainly applies the ground-to-air transient electromagnetic method to conduct a hydrogeological engineering geological survey in a mine subsidence area. By using this method effectively, changes in hydrogeological and engineering geological conditions in the mine subsidence area are identified and water filling conditions below section 310 and section 250 of the roadway are determined. This study provides accurate and reliable basic data support for rescue operations and post-disaster reconstruction efforts, while also offering valuable insights for similar exploration projects.

ENGINEERING PREPARATION OF THE SOIL BASE FOR THE FOUNDATIONS OF THE CONSTRUCTIONS OF THE DERHACHI SOLID WASTE LANDFILL

After conducting engineering and geological investigations, it became necessary to provide scientific support for construction in terms of engineering preparation of the soil base for the foundations of the structures due to extreme unsustainability in the plan and depth of the rocks. Such engineering-geological conditions significantly impact the choice of foundation structures and the justification of measures to reduce or eliminate the negative effect on the environment and the development of dangerous geological processes and phenomena. We thoroughly studied the deformation and strength properties of the supporting soil layers and developed recommendations for their engineering preparation and improvement of the indicators. Bulk soil is present in local depressions: construction debris, sand, and compacted loam. Based on the analysis of physical and mechanical properties, we could conclude that this soil cannot be used as a soil base for the foundations of buildings due to its loose composition and enrichment with organic substances and must be completely replaced during the production of earthworks. They can be used as a basis for laying engineering networks. After excavation pits for individual columns, before setting up the preparation, it is necessary to carefully inspect the soil foundation to ensure that it is the same engineering and geological element specified in the project. The soil base of the foundations is redeposited subsidence loess loams, which have mostly lost their subsidence properties, but local inclusions with subsidence properties have remained in the thickness of these soils. If there are lenses of soils in the soil base with indicators of physical and mechanical characteristics that are lower than those adopted in the project and that have a thickness of less than one meter, they should be removed and replaced with sand or sand-crushed soil with layer-by-layer compaction and compaction quality control. Doing so will create the same soil conditions for the building foundation. The performed scientific and technical support of the construction made it possible to choose a method of technical soil reclamation—partial replacement of weak soils with sand and crushed stone, which, after layer-by-layer compaction, can withstand a significant load and stability under vibrational influences. Keywords: landfills, solid household waste.

Статистические характеристики расчета приращений сейсмической интенсивности при сейсмическом микрорайонировании горных территорий

Introduction. During seismic micro-zoning of a territory, one of the main instrumental methods for calculating intensity increments is the registration of earthquakes in areas with different soil conditions. In this case, the calculation of increments is based on the amplitudes of oscillations simultaneously in the given and reference sections. The purpose of the work is to compare the increments in various expressions obtained for powerful vibration and pulse sources, as well as for an instrumental measure of seismic intensity. Materials and methods. Processing of instrumental data, their systematization and description using basic statistical indicators. The analysis was carried out using data from the Vladikavkaz network - records of earthquakes obtained simultaneously at four seismic stations located in areas with different ground conditions. Results. To check the formulas for calculating seismic intensity increments and comparing them with the obtained data, distribution histograms and the corresponding probability density functions were constructed, under the assumption that the distribution is normal. All methods for calculating vibration amplitudes gave identical results in ranking areas according to the degree of seismic hazard, however, taking into account rounding, an increase in intensity by 1 point is not always achieved in an area where, due to the worst soil conditions. The best results for calculating intensity increments were obtained for the area values of the velocity and acceleration spectra. At the same time, the areas of the acceleration spectra provide better differentiation of soil conditions according to the degree of danger (with the same coefficient in front of the logarithm). Discussion. The task of developing an instrumental method of seismic micro-zoning is to clarify the coefficients in front of the logarithmic scale of the quantities under consideration, the reduction of which, in turn, determines the clarification of the level of impacts for given intensities. On the other hand, smaller coefficients lead to worse differentiation of soil conditions of areas when calculating increments of seismic intensity. The solution to the problem may lie somewhere at the junction of both approaches. Conclusion. Analysis of the results shows a connection between the magnitude of the distribution dispersion and the complexity of the engineering-geological conditions of the site. The more factors influence the wave processes in the soils, the greater the scatter of values around the average. Main factor is a multi-layered environment, i.e. the presence of reflective boundaries, and the other one is the very properties of the medium, i.e. its dispersion. Resume. Results are useful in differentiating soil conditions by an additional parameter that affects the probability of failure to exceed the calculated values of seismic impacts - the same average values of seismic intensity can be characterized by different confidence intervals; from a practical point of view, one should set the same probability of not exceeding the design impact values. Suggestions for practical applications and directions for future research. For practical applications it is necessary to distinguish the influence of the layering of the medium and the direct dispersion of the soils composing the stratum, which represents the next research task.

Investigating the influence of the engineering geological conditions on vibration propagation near the embankment induced by high-speed trains

Investigating the influence of the engineering geological conditions on vibration propagation near the embankment induced by high-speed trains

A Case Study for Stability Analysis of a Toppling Bank Slope with Fault Fracture Zones Developed under the Action of Bridge Loads and Reservoir Water

The mountainous areas of Southwest China have the characteristics of valley deep-cutting, a large topographic gradient, complex geological structures, etc. With the development of infrastructure construction in the area, the construction of bridges across valleys has gradually increased, and the phenomenon of slope failure occurs more and more frequently. As the weak interlayer, the fault fracture zones have a significant influence on the geological structure and stability of slopes, while the complexity of the mechanism of the deformation and failure of slopes increases with the combination of the development of the fracture zones and toppling deformation. This paper took the toppling bank slope of bridge foundations developed with fault fracture zones in Lancang River as the research object. Through an on-site field survey and geological survey technologies, it identified the distribution range of the fracture zones on the bank slope and determined the characteristics of the rock mass in the fracture zones. A stability evaluation model for the bank slope of the bridge foundations was established using the limit equilibrium method and discrete element method. Based on the two-dimensional limit equilibrium analysis, the potential failure modes of the bank slope were explored, and the stability of the bank slope under bridge loads was calculated. Through the three-dimensional geological model of the bank slope, including the fracture zones and toppling bodies, the three-dimensional discrete element numerical simulation method was adopted to simulate and calculate the deformation and failure process of the bank slope under different bridge loads and working conditions. According to the calculation results, the influence of bridge loads and reservoir water on the stability of the bank slope was analyzed from the perspectives of displacement, plastic zone, stability coefficient, and other factors. The formation process of the plastic zone and the development of the sliding surface were revealed, the incentive mechanism of bridge loads and reservoir water on the deformation and failure of the bank slope was analyzed, and the influence of fault fracture zones on the stability of the bank slope and the development of toppling deformation was determined. The results indicate that the fault fracture zones are important geological structures that affect the deformation and failure of the bank slope as a weak interlayer. Under the influence of bridge loads and reservoir water, the stability of the bank slope is affected by the quality of the rock mass and the development of the fault fracture zones, resulting in the unmet need for safety requirements and maybe leading to instability. Based on the calculation results of the stability evaluation prediction model for the bridge foundation bank slope and the engineering geological conditions, the bridge scheme has been selected.

Geological Mapping and Stand-up Time Estimation based on Core Drilling Evaluation using Rock Mass Rating Method on The Main Spillway and Diversion Tunnel at Manikin Dam, Kupang Regency, Nusa Tenggara Timur

The Main Spillway and Diversion Tunnel at Manikin Dam is one of the dams under construction in the Kupang City area, where several soil or rock investigations have been carried out around it. However, the field investigations are not accompanied by a surface geological investigation or evaluation of subsurface geological conditions based on core drill results. Therefore, the purpose of this paper is to evaluate the engineering geological condition in tunnel construction by displaying surface and subsurface geological mapping with a scale of 1:10,000 and evaluate samples of core drilling using the Rock Mass Rating method in order to have more accurate stand-up time assumptions. The result of engineering geological mapping shows that the research area has three lithologies, namely a basalt unit, a carbonaceous sandstone unit, and a scaly claystone with a chaotic rock unit. The core-drill evaluation indicates that the research area is classified into three quality rock masses, namely Good Rock with an RMR Rating of 64, Fair Rock with an RMR Rating of 46, and Poor Rock with an RMR Rating of 36. The stand-up time value for each rock mass quality category is obtained from the quality rock mass results. The stand-up time value for the Good Rock category is 2200 hours, the Fair Rock category is 30 hours and the Poor Rock category is 1.2 - 1.7 hours. Based on the low stand-up time values in the Fair Rock and Poor Rock categories, it is expected that a support system will be installed immediately after tunnel excavation.