Engineering Geological Investigations Research Articles

Sedimentation characteristics of surficial sediments in Baiyun Canyon area, Northern South China Sea

The Baiyun Canyon area on the Northern Slope of the South China Sea is a potential hotspot for oil and gas resource development, but the sediment characteristics and sedimentary environment in this region present challenges for offshore engineering. This study comprehensively analyzed the physical, and mechanical properties of sediments in the area using geophysical exploration, engineering geological investigation, fixed-point sampling and hydrological observation. The engineering geological characteristics and sedimentary environment of surface sediments in the Baiyun Canyon area were studied, and the relationship between physical and mechanical properties and sedimentary environment was explored. The study revealed that the sediments in this area consist mainly of organic soft clay with high water content, low density, high pore ratio, high liquid limit, high plasticity and low strength. The physical and mechanical properties of the sediments vary, with the mechanical properties exhibiting higher variability than the physical properties. The research findings offer a scientific basis for understanding the seabed soil properties for designing submarine engineering structures in the deep waters of the northern South China Sea. This study holds significant theoretical and practical implications for oil and gas exploration and offshore engineering construction.

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.

Effect of slope angle on fractured rock masses under combined influence of variable rainfall infiltration and excavation unloading

Intense precipitation infiltration and intricate excavation processes are crucial factors that impact the stability and security of towering and steep rock slopes within mining sites. The primary aim of this research was to investigate the progression of cumulative failure within a cracked rock formation, considering the combined effects of precipitation and excavation activities. The study was conducted in the Huangniuqian eastern mining area of the Dexing Copper Mine in Jiangxi Province, China. An engineering geological investigation was conducted, a physical model experiment was performed, numerical calculations and theoretical analysis were conducted using the matrix discrete element method (MatDEM), and the deformation characteristics and the effect of the slope angle of a fractured rock mass under different scenarios were examined. The failure and instability mechanisms of the fractured rock mass under three slope angle models were analyzed. The experimental results indicate that as the slope angle increases, the combined effect of rainfall infiltration and excavation unloading is reduced. A novel approach to simulating unsaturated seepage in a rock mass, based on the van Genuchten model (VGM), has been developed. Compared to the vertical displacement observed in a similar physical experiment, the average relative errors associated with the slope angles of 45°, 50°, and 55° were 2.094%, 1.916%, and 2.328%, respectively. Accordingly, the combined effect of rainfall and excavation was determined using the proposed method. Moreover, the accuracy of the numerical simulation was validated. The findings contribute to the seepage field in a meaningful way, offering insight that can inform and enhance existing methods and theories for research on the underlying mechanism of ultra-high and steep rock slope instability, which can inform the development of more effective risk management strategies.

An indicator of relative distribution probability of field-scale permafrost in Northeast China: Using a particle swarm optimization (PSO)-based indicator composition algorithm

Under the influence of climate changing, permafrost in Northeast China (NEC) has been consistently degrading in recent years. Numerous scholars have investigated the spatial and temporal distribution patterns of permafrost in the NEC region. However, due to constraints in data availability and methodological approaches, only a limited number of studies have extended their analyses to the field scale. In this study, we established a particle swarm optimization (PSO)-based indicator composition algorithm (PSO-ICA) to obtain an indicator factor, η, that indicates the relative distribution probability of permafrost at the field scale. PSO-ICA screened and combined 12 high-resolution environmental variables to compose η. The spatial distribution data of permafrost with a length of 765.378 km provided by the engineering geological investigation report (EGIR) of six highways were used to train and validate the effectiveness of η in indicating permafrost. At the field scale, η was found to be similar to the surface freezing number (SFN) in its ability to indicate permafrost, with AUC values of 0.7046 and 0.7063 for the two by the ROC test. In addition, η has a good performance in predicting highway distresses in the permafrost region in the absence of survey data. This study also confirmed that the resolution and accuracy of permafrost mapping results can be improved by utilizing η. After downscaling the 1 km resolution SFN to 30 m resolution using η, the R2 of the linear relationship between SFN and permafrost temperatures from 43 monitoring boreholes was improved from 0.7010 to 0.8043. If η can help understand the distribution of permafrost at field scale, many engineering and environmental practices could potentially benefit.

Engineering Geological Investigation of the Katar Dam Foundation and Abutment Slope Stability Analysis, Southeast Ethiopia

Engineering Geological Investigation of the Katar Dam Foundation and Abutment Slope Stability Analysis, Southeast Ethiopia

Engineering geological and geotechnical evaluation of Sathya Sai Prasanthi Nilayam railway tunnel, Andhra Pradesh, India

Detailed engineering geological investigations were carried out for a railway tunnel which was constructed more than two decades ago. 3D engineering geological mapping was carried out using Brunton Compass and Total Station Surveying instruments in 1:100 scale. Coarse-grained pink and grey granite, hornblende-biotite gneiss and dolerite dyke of Archaean age and Lower Proterozoic age were mapped. Rock mass was intersected by sub-horizontal, inclined, and vertical joint sets, which were continuous and persistent, smooth, and planar with thick filling of decomposed and crushed sheared material or with thin coating of clay material. Based on the Q-system, rock mass was classified into different classes. On the basis of large-scale engineering geological mapping and Norwegian Method of Tunnelling, a support system was recommended which includes rock bolt, fibre reinforced shotcrete, grouting and reinforced ribs of sprayed concrete and the same is implemented by the agency. As per the best knowledge of the authors, reinforced ribs of sprayed concrete are first time used for transportation tunnels in India and it will be more effective if it will be compared with ISMB or Lattice Girder.

Forecasting and early warning of shield tunnelling-induced ground collapse in rock-soil interface mixed ground using multivariate data fusion and Catastrophe Theory

The high spatial variability of the rock-soil interface (RSI) in complex geological conditions introduces strong uncertainties in both subsurface stratigraphy and geotechnical properties. Inaccurate interpretation of such uncertainties during engineering geology investigations increases the geohazard risk of excessive surface settlement or even severe catastrophic ground collapse when shield machines are excavating in RSI mixed ground. Prediction and early warning of excessive surface settlement are necessary measures to address such a risk; however, unavoidable drawbacks such as overfitting, insufficient accuracy, and ineffectiveness remain in existing prediction models and early warning algorithms and have posed significant challenges. In this study, a novel framework using both a multivariate data fusion prediction model and a dynamic early warning algorithm was developed for forecasting and early warning of ground collapse during shield tunnelling in RSI mixed ground. The prediction model is the Differential Evolutionary Optimized Quadratic Taylor Series Extended Kalman Filter (DEQT-EKF); the early warning algorithm is based on Catastrophe Theory and uses the Gradient Ratio (GR) criterion to identify catastrophic singularities. The practicality and accuracy of the framework are well verified by a subway shield tunnelling-induced ground collapse incident in East China with complex RSI mixed ground conditions. The prediction results are compared with the surface settlement measurements and good agreement is obtained, indicating that the DEQT-EKF model can achieve satisfactory accuracy in predicting excessive settlement. The use of the GR criterion can trigger the early warning one time step before the ground collapse event, indicating that it is a competent and practical early warning strategy for shield tunnelling-induced ground collapse. The framework has the potential to significantly reduce the risk of ground collapse caused by geological uncertainties when constructing shield tunnels through complex ground conditions.

Spatial stratified heterogeneity analysis of field scale permafrost in Northeast China based on optimal parameters-based geographical detector.

Affected by global warming, the permafrost in Northeast China (NEC) has been continuously degrading in recent years. Many researchers have focused on the spatial and temporal distribution characteristics of permafrost in NEC, however, few studies have delved into the field scale. In this study, based on the Optimal Parameters-based Geographical Detector (OPGD) model and Receiver Operating Characteristic (ROC) test, the spatial stratified heterogeneity of permafrost distribution and the indicating performance of environmental variables on permafrost in NEC at the field scale were analyzed. Permafrost spatial distribution data were obtained from the Engineering Geological Investigation Reports (EGIR) of six highways located in NEC and a total of 19 environmental variables related to heat transfer, vegetation, soil, topography, moisture, and ecology were selected. The H-factors (variables with the highest contribution in factor detector results and interaction detector results): slope position (γ), surface frost number (SFN), elevation (DEM), topographic diversity (TD), and annual snow cover days (ASCD) were found to be the major contributors to the distribution of permafrost at the field scale. Among them, γ has the highest contribution and is a special explanatory variable for permafrost. In most cases, interaction can improve the impact of variables, especially the interaction between H-factors. The risk of permafrost decreases with the increase of TD, RN, and SBD, and increases with the increase of SFN. The performance of SFN to indicate permafrost distribution was found to be the best among all variables (AUC = 0.7063). There is spatial heterogeneity in the distribution of permafrost on highways in different spatial locations. This study summarized the numerical and spatial location between permafrost and different environmental variables at the field scale, and many results were found to be informative for environmental studies and engineering construction in NEC.

Engineering Geological and Geophysical Investigations to Characterise the Unstable Rock Slope of the Sopu Promontory (Gozo, Malta)

Different engineering geological and geophysical investigations were performed at the Sopu promontory in the island of Gozo (Malta), involved in an impressive lateral spreading process due to the superimposition of a stiff limestone (ULC) on a ductile clay (BC). The applied techniques include: traditional geological and engineering geological surveys, unmanned aerial vehicles (UAV) survey, electrical resistivity tomography (ERT) survey, ground-penetrating radar (GPR) investigations, single-station seismic ambient noise measurements, and array seismic ambient noise measurements. The integration of the obtained results allowed us to reconstruct a subsoil model of the promontory that includes features related to the local geology of the slope and to the landslide process, as well as to define a conceptual model that describes the main evolution phases of the expansion process. The presence of back-tilted rock blocks with no features of polarization of Rayleigh waves evidenced the different failure mechanism of the rigid UCL plateau at the Sopu promontory with respect to the Selmun promontory, located in the close island of Malta, where the lateral spreading due to the same geological setting tends to produce unstable rock blocks with a toppling mechanism. This result encourages further future observations and analyses of this topic.

Assessment of rock mass properties and load-bearing potential in low-grade metamorphic rocks: A study from the Tigray region, Ethiopia

<p>This study presents an engineering geological investigation aimed at assessing the bearing capacity of the proposed site for the Meli gold processing plant (GPP) located in the northwestern region of Tigray, Ethiopia. The geological composition of the site predominantly comprises low-grade metamorphic rocks, with intermediate metavolcanic rocks being the most prevalent. This research utilized an innovative combination of empirical methodologies, including the Hoek–Brown and Mohr–Coulomb criteria, to evaluate the strength and elasticity characteristics of the rock mass. Additionally, the rock mass foundation for the GPP was rigorously classified using renowned systems such as the rock mass rating (RMR), quality index (Q), and geological strength index (GSI). Employing five different empirical equations to estimate bearing capacity, this study significantly advances our understanding by comparing these diverse methodologies, which is a novel approach in this geological context where engineering property data are scarce or non-existent. The bearing capacities determined using the Hoek–Brown and Mohr–Coulomb criteria ranged from 11.6 to 46.2 MPa and 7.9 to 10.5 MPa, respectively. These findings not only offer valuable insights into the assessment of bearing capacity in metamorphic rock formations but also underscore the effectiveness of combining multiple empirical approaches to enhance the reliability of geological assessments. This research contributes to the advancement of construction practices and enhances project planning strategies in comparable geological environments, particularly highlighting the utility of robust empirical data in the absence of extensive drilling data. By integrating comprehensive empirical analyses, the study provides a methodological framework that significantly aids in informed decision-making for future projects located in similar geological settings.</p>

Exploring the potential of smartphone photogrammetry for field measurement of joint roughness

Rock joints play a crucial role in determining the behavior and stability of rock masses. Despite their importance, there is a lack of devices for easily and accurately measuring joint roughness in field conditions. This research explores the potential of smartphone photogrammetry as a solution for large-scale joint roughness mapping. A large natural rock joint from an open pit mine in Yunnan, China, served as the specimen. Both two dimensional (2D) and three dimensional (3D) roughness parameters were utilized to characterize joint roughness. The study found that the accuracy of smartphone photogrammetry is acceptable when operated with guidance. The measurement errors were 1.7%, 4.7%, 7.8%, and 6.1% for the Z1, Ai, Z2, and PSD-D roughness parameters, respectively. In conclusion, this study demonstrates that using smartphone photogrammetry as a portable and cost-effective method for measuring joint roughness in field conditions has the potential to significantly benefit engineering geological investigations.

Long-term hydrological monitoring of soils in the terraced environment of Cinque Terre (north-western Italy)

Terraced landscapes represent one of the most widespread human-induced/man-made transformations of hilly-mountainous environments. Slope terracing produces peculiar morphologies along with unusual soil textures and stratigraphic features, which in turn strongly influence slope hydrology. The investigation of the hydrological features of terraced soils is of fundamental importance for understanding the hydrological dynamics occurring in these anthropogenic landscapes, especially during rainfall events. To this purpose, the availability of extensive field monitoring data series and of information on subsoil properties and structure is essential. In this study, multi-sensor hydrological data were acquired over a period longer than 2 years in the experimental site of Monterosso al Mare, in the Cinque Terre National Park (Liguria region, Italy), one of the most famous examples of terraced landscape worldwide. Monitoring data were coupled with accurate engineering-geological investigations to achieve the hydro-mechanical characterization of backfill soils and to investigate their hydrological response at both the seasonal and the single rainstorm scale. The results indicated that the coarse-grained, and anthropically remolded texture of the soils favors the rapid infiltration of rainwater, producing sharp changes in both soil volumetric water content and pore water pressure. Furthermore, the pattern of hydrological parameters showed seasonal trends outlined by alternating phases of slow drying and fast wetting. The study outcomes provide useful insights on the short and long-term evolution of hydrological factors operating in agricultural terraces. These findings represent a useful basis for a better understanding of the time-dependent processes that guide water circulation in terraced systems, which have a key role in controlling the occurrence of erosion and landslide processes.

A Stability Analysis of an Abandoned Gypsum Mine Based on Numerical Simulation Using the Itasca Model for Advanced Strain Softening Constitutive Model

An abandoned gypsum mine has been discovered beneath the route of a highway construction in Hunan province, south China. Due to the highway construction and operations safety, there is an urgent need for a comprehensive stability analysis of the abandoned mining area. The 3D laser scanning detection technique has been adopted, and over 400 drillholes were strategically placed near the highway to capture the spatial information of the abandoned gypsum mine. The ore body has an average mining thickness of about 3 m, and the depth of the mining roof ranges from 40 to 60 m, with an average span of 16 m. Based on the research achievements in the engineering geological investigation, rock mass quality assessment, and geometry information, a simplified numerical model has been established for stability analysis. The numerical model employed the IMASS rock mass constitutive model to conduct a stability analysis of the abandoned gypsum mine during the excavation process and in the medium to long term. The IMASS constitutive model can effectively reflect the entire process of rock mass from microscopic damage to macroscopic instability, and the numerical simulation of current and long-term stages provides a much greater understanding of the mining room stability and the effect of various geo-mechanical parameters not considered in traditional empirical methods. The abandoned gypsum mine stability is guaranteed in the mining and current stages. However, the numerical results showed that a 0.4 m spalling thickness of the sidewalls can cause an overall instability and failure of the abandoned mine, and reinforcement measures must be taken for long-term safety. The stability of the abandoned gypsum mine with filling solutions was also evaluated numerically.

Simulation of Spatiotemporal Distribution and Variation of 30 m Resolution Permafrost in Northeast China from 2003 to 2021

The high-resolution permafrost distribution maps have a closer relationship with engineering applications in cold regions because they are more relative to the real situation compared with the traditional permafrost zoning mapping. A particle swarm optimization algorithm was used to obtain the index η with 30 m resolution and to characterize the distribution probability of permafrost at the field scale. The index consists of five environmental variables: slope position, slope, deviation from mean elevation, topographic diversity, and soil bulk density. The downscaling process of the surface frost number from a resolution of 1000 m to 30 m is achieved by using the spatial weight decomposition method and index η. We established the regression statistical relationship between the surface frost number after downscaling and the temperature at the freezing layer that is below the permafrost active layer base. We simulated permafrost temperature distribution maps with 30 m resolution in the four periods of 2003–2007, 2008–2012, 2013–2017, and 2018–2021, and the permafrost area is, respectively, 28.35 × 104 km2, 35.14 × 104 km2, 28.96 × 104 km2, and 25.21 × 104 km2. The proportion of extremely stable permafrost (<−5.0 °C), stable permafrost (−3.0~−5.0 °C), sub-stable permafrost (−1.5~−3.0 °C), transitional permafrost (−0.5~−1.5 °C), and unstable permafrost (0~−0.5 °C) is 0.50–1.27%, 6.77–12.45%, 29.08–33.94%, 34.52–39.50%, and 19.87–26.79%, respectively, with sub-stable, transitional, and unstable permafrost mainly distributed. Direct and indirect verification shows that the permafrost temperature distribution maps after downscaling still have high reliability, with 83.2% of the residual controlled within the range of ±1 °C and the consistency ranges from 83.17% to 96.47%, with the identification of permafrost sections in the highway engineering geological investigation reports of six highway projects. The maps are of fundamental importance for engineering planning and design, ecosystem management, and evaluation of the permafrost change in the future in Northeast China.

A comparative study of workability classes using seven case studies of engineering-geological investigations of sewer systems in Northern Moravia

While the main focus of numerous engineering-geological investigations is to determine load-bearing capacity and settlement in engineering structures, this article aims to point at the specificity of sewer system engineering-geological investigations, which focuses on workability of soils and rocks. The study deals with workability class assessment of seven different sewer system localities. The significance of this research lies in the mutual comparison of workability class assessment of these seven localities in terms of two different workability standards. Each of the standards represents an independent model of assessment and classification of workability. The first standard (CSN 73 1001) classifies soils and rocks into seven workability classes, while the second (EN ISO 14688) comprises only three workability classes. Each of the approaches has its advantages and disadvantages. In comparison to the first one, the second standard permits faster and easier classification of rocks, but may be less fair to investors or developers when considering the real engineering-geological conditions and costs of implementation. Rocks were newly classified into three (easy, medium and difficult) categories of earthwork realization difficulty. In the study, 33 layers were classified in the category of easy realization of earthworks, 8 layers in the category of a medium degree of earthwork realization difficulty, and two layers in the category of a difficult realization of earthworks.

Numerical Simulation Research and Application of Support Design of Broken Rock Mass in Submarine Gold Mine

In order to solve the problem that the broken rock mass is easy to collapse and fall during the excavation of a submarine gold mine, two kinds of bolt-mesh-concreting combined support schemes are designed by means of field engineering geological investigation, indoor rock mechanics test, rock mass quality classification, and theoretical analysis. We use the numerical simulation for verification and carry out the field industrial test. The results show that the stability grade of broken surrounding rock is III–IV; both schemes can effectively control the deformation and failure of surrounding rock. Compared with the unsupported scheme, the maximum roof displacement in the scheme using roadway roof and sidewall support is reduced by 26.9%, the maximum thickness of the roof plastic zone is reduced by 58.2%, and the volume of the surrounding rock plastic zone is reduced by 26.32%. The bolt-mesh-shotcrete support has good control effect on the loose deformation of surrounding rock, which can effectively prevent the roof collapse and sidewall spalling of roadway. The field industrial test of support scheme meets the stability control requirements of broken rock mass in mines, and the application effect is obvious. The research results presented in this study provide valuable technical guidance and essential insights for the design of support systems in other similar mining projects, contributing to the effective control and stability of broken rock masses during excavation.

EXCASS system and Rock Mass Rating (RMR) classification for determining excavation method and tunnel support at Pelosika Dam Spillway Tunnel

Pelosika dam spillway tunnel was designed to drainage flood discharge and prevent overtopping. In recent investigations, the rock mass classification has not been done specifically in the spillway tunnel. This research aims to obtain technical geological data and information to define excavation methods and tunnel support. For more comprehensive research, engineering geological investigations were carried out regarding the Geological Strength Index (GSI), selecting excavation methods using EXCASS system and Rock Mass Rating (RMR) for tunnel support. The geological mapping showed that the study site was composed of 2 lithological units: quartz muscovite phyllite and pebblely sand deposits. The GSI value in the tunnel is between 14-25, indicating poor and very poor quality. Adopting the EXCASS system, the optimum method of excavation (EPIopt) in the Pelosika dam spillway tunnel are ripper easy and digger. While RMR values of 9 – 25 are classified as poor quality. Consequently, the appropriate method for the excavation sequence is using the top heading and bench and multiple drifts. And the recommended support system is a systematic rock bolt with wire mesh and shotcrete in the crown and walls with medium to light steel rib.

Breccia for Diversion Tunnel Construction at Bener DAM in Purworejo, Central Java, Indonesia: Fragments, Matrix, RMR

This study aimed to explain the detailed engineering geology investigation which has breccia geological units on Diversion Tunnel at Bener Dam, Purworejo Regency, Central Java Province. The investigation includes geological conditions both breccia fragment and matrix, to Rock Mass Rating (RMR) values each unit. The data were taken from face mapping tunnel with interval 10 meters at inlet 1-390 and 841-865 meters. The findings showed that geological engineering units consisted of Monomict Breccia. The geological units can be divided into geological engineering; Monomict Breccia Matrix (RMR 72-92), Polymict Breccia Matrix (RMR 82), Andesite Fragmen (RMR 52-62), and Tuff Fragmen (RMR 79-84). The discovery of Andesite and Tuff Fragments needs to be handled differently than Monomict Breccia or Polymict Breccia. Andesite Fragment unit with discontinuity of sheeting joint requires rock bolt reinforcement to be installed perpendicular to the discontinuity plane. While the dominant unit is the Tuff Fragment which has a UCS value of 5-7 MPa, it is not recommended to use the blasting excavation method even though it has an RMR value of 79-84.

Engineering-geological comparative analysis of four cases studies of waste landfills

The aim of the paper is to carry out a comparative engineering-geological study of four different waste landfills using the evaluation criteria for the geological subsoil as a natural sealing barrier. The study evaluates 4 localities (Velké Pavlovice, Kvítkovice, Prakšice and Horní Suchá) using three variants (based on two standards) which approach the geological barrier requirements as a combination of impermeability requirements based on a filtration coefficient limit value. and the required geometry represented by investigation depths. The research was carried out in landfills in Moravia, in the east of the Czech Republic. The study’s motivation is to point at the differences in engineering-geological investigations of waste landfills (as for the requirements for impermeable geological subsoil as a natural sealing barrier) when compared with other engineering structures (where the main goal is to evaluate load-bearing capacity and settlement). The purpose of the geological barrier is to prevent the spread of contamination, and the paper shows this can be approached differently, as shown in two different methodologies investigated herein. The first model (Model 1) assumes there is a 3-m-thick subsoil below the landfill’s footing bottom, which manifests impermeability characterized by the filtration coefficient Kf ≤ 1.0 * 10–9 m/s, or a 30-m-thick subsoil of Kf ≤ 1.0 * 10–8 m/s. The second model (Model 2) assumes a 1-m thick, impermeable subsoil massif of Kf ≤ 1.0 * 10–9 m/s. We found that none of the landfills in the four selected localities had an impermeable layer in the required depth (a filtration coefficient Kf from 1.8 * 10–9 to 3.9 * 10–9 m/s), and thus did not comply with the limiting conditions. As a result, an anthropogenic technical barrier had to be installed. An important goal of the study from an environmental point of view was to assess the existence of a suitable geological barrier under the proposed landfills. The most important criterion from this point of view is permeability. An additional technical objective of the project was also the assessment of the possible creation of a technical anthropogenic isolation barrier. In the event that the natural sealing barrier would not be sufficient. This was shown in all solved case studies of engineering geological investigations of waste landfills.

Characteristics and mechanism of large deformation of squeezing tunnel in phyllite stratum

The Maoxian Tunnel in Sichuan, China has experienced significant deformation and supporting failure in the surrounding phyllite rock. To address this problem, on-site engineering geological investigation and testing methods were deployed in the present study to examine the characteristics and mechanism of deformation in the tunnel. Scanning electron microscopy, rock hydraulic tests, and uniaxial compressive tests were used to investigate the hydraulic and mechanical properties of the surrounding rock, and to examine the mechanisms underlying the significant deformation. The results suggest that the large deformation in Maoxian Tunnel is a result of shear expansion and progressive failure of the soft rock under high stress. To enhance the integrity and self-sustaining ability of the rock mass, it is necessary to promptly construct support structures and reinforce the surrounding rock.