Geotechnical Exploration Research Articles

Soil water characteristic curve parameters of collapsible sand in Lambayeque, Peru

Several structures are built on collapsible soils in the mining and petroleum industries and on civil sites. In order to analyze the stability of such structures, one must properly study the unsaturated soil behavior. Collapsible soils are frequent sand soil that are susceptible to a significant and sudden reduction in volume upon wetting. An important factor is matric suction, which es related to moisture content through the soil water Characteristic Curve (SWCC), the SWCC is obtained through a filter paper technique and provides a valuable relationship between suction and water content unique to soils. This measures the influence of parameters on the behavior of the structure of collapsible soil. Interactions between structure and soil must be properly evaluated as the bearing capacities of shallow and deep foundations are linked to properties of soil suction, moisture, and grade saturation. This work has experimentally measured the parameters of suction and moisture on the behavior of collapsible sands, where an oil storage tank will be built in the city of Lambayeque in Peru. Undisturbed soil specimens obtained from geotechnical exploration campaigns were used. The filter paper method used in this study was that proposed by models of Brooks-Corey and Van Genuchten. Results show consistent values near reported values from literature.

LOCATION OF THE REFRIGERATION HALL ON THE BASIS OF THE GEOTECHNICAL STUDY IN THE PERIURBAN AREA OF CRAIOVA

The geotechnical exploration works performed in the site area aim to provide the data necessary to solve the issues related to location and morphological data, classification in the geotechnical category, investigation of the foundation land, data on lithology and physicalmechanical characteristics of the land, foundation conditions. In this sense, two geotechnical drillings were performed, dynamic penetration tests and the stratification, granulometry and physical and mechanical characteristics were studied. From the analysis of the obtained results it results that the site has a slight slope with EV orientation, it is stable when sliding, the ground is good for foundation on 0.0-6.0 m depth, the aquifer horizon is over 7.0 m depth, the values of conventional pressure are of 189 kPa for Df = 0.8 m and B = 0.6 m and respectively 288 kPa for Df = 4.0 m and B = 2.0 m, the land presents a moderate geotechnical risk and a degree of seismicity 82

Geological and Geophysical Study in Udheri Khola Area, Nalgad Hydroelectric Project, Jajarkot District, Lesser Himalaya, Western Nepal

Subsidence in carbonate rock is one of common and challenging action in terms of engineering construction. Geological study and geophysical investigation carried out in the intake area of Nalgad Hydroelectric Project Jajarkot, western Nepal Lesser Himalaya. The main objective was to identify the cause of subsidence in the intake area of Nalgad Hydroelectric Project, Jajarkot. Geological study of the area was carried to understand the lithology, thickness and structure of the area.
 The study area comprises two distinct rock units, namely, Dolomite Unit followed up by the Slate Unit. The Dolomite Unit is composed of light grey to grayish white stromatolitic dolomite which is thrusted over the Slate Unit near to Laikham village and Sepu Khola area. The Slate Unit is made up of grayish black to graphitic slate. A thin prominent calcareous horizon wasconfined between Slate Unit.
 2D-Electric Resistivity Tomography (ERT) measurements were deployed in four different lines to investigate the cause of the subsidence in the carbonate terrain. A concentric very high resistivity patch shown by Tomogram ER-D-01 survey line was identified and interpreted as dry cavity. The result of the 2D- ERT survey was correlated with core log data of geotechnical exploration in the suspicious point to ensure the presence of karst in the Dolomite Unit at right bank of Nalsyagu Khola near dam axis of Nalgad Hydroelectric Project. The 2D – ERT survey together with geotechnical investigation is capable of identifying subsurface karst feature as the cause of surface collapse in the area.

Seismic failure of an old pier during the 2014 Mw8.2, Pisagua, Chile earthquake

The seismic failure of an old quay wall, built in 1932, located in the Port of Iquique during the Mw8.2, 1 April, 2014, Pisagua, Chile earthquake is studied. A geotechnical exploration, including boreholes, cone penetration test (CPT) soundings, and surface-based geophysical techniques were performed to characterize the materials forming the pier. The data and field observations were analyzed and used to develop a geotechnical finite element (FE) model of two cross-sections, to define the most likely mechanism to explain the failure. The FE results are compared against the deformations measured in a number of cross-sections of the pier, suggesting that the failure can be explained by a combined effect of the dynamic increase in lateral earth pressures and the base rotation of the confining walls due to the lack of proper compaction of the rockfill prism below the confining walls.

Risk Assessment for Karst Hazards at a Facility in Saudi Arabia—A Case Study

The boom in industrial and infrastructure construction in Saudi Arabia requires in-depth knowledge of the underground conditions to build a sustainable project. This paper gave a practical example of the challenges facing an existing facility built on a karstic limestone formation in 1970’s. Multiple geophysical techniques such as Microgravity, Electrical Resistivity Imaging, Vertical Seismic Velocity Profiling, Cross Hole Seismic Tomography, Ground Penetration Radar, Multi-Channel Analysis of Surface Waves, as well as boreholes and down-hole video imagery, were deployed through the journey of assessing the karst associated hazards of potential sinkholes or general subsidence. This paper described the karst processes, site geology, geophysical and geotechnical exploration program, and characterizes the subsurface karst conditions at the eastern province of Kingdom of Saudi Arabia. Results and findings of preliminary, geotechnical and geophysical investigations have been utilized to identify the major factors influencing the karst formation. Analyses and integration of obtained results to estimate the type and magnitude of risk affected the major components of industrial facility at the project site using well-known statistical approach were presented in this paper. Consequently number of remedial measures implemented to combating the experienced and expected karst hazards at the studied industrial facility placed in karstified landform are given. A model for using integrated geophysical and geotechnical techniques to assess karst-related risks to a facility was further explored herein.

Assessment and analysis of the slope stability landfill mining waste on the location "Brvenica" - Raška

For the purposes of the Project Cadastre of Mining Waste in the Republic of Serbia.", implemented by the association PLEJADES GmbH - Independent Experts and DMT GmbH & Co. KG, Germany, the Mining and Metallurgy Institute Bor has performed the geotechnical exploration and testing in order of the slope stability assessment of the mining waste facilities.

Excessive groundwater inflow during TBM tunneling in limestone formation

A sudden increase of groundwater inflow of 670 tons a day was experienced during tunneling in a limestone formation at around 53 m below the ground surface. The limestone cavities were expected to be located at 5–10 m or more above the tunnel crown in geotechnical exploration. However, limestone cavity network was encountered at the tunnel depth, and large groundwater inflow was experienced. Because of the excessive groundwater inflow into the tunnel, the groundwater level dropped to GL-32 m from the original level of GL-16 m, and consequently maximum of 23 mm of ground settlement and damage of adjacent structures took place. In this study the change of groundwater regime during tunneling in limestone area containing cavity network was analyzed through 3-dimensional numerical analysis, and the mechanism of groundwater level drawdown followed by ground subsidence was analyzed by comparing measurements and numerical analysis results. And also the analytical solution for determining the range of cutoff grouting was proposed to minimize groundwater inflow during excavation in a fractured zone.

Structure, substance and near-surface magmatic chambers of Mutnovsky and Gorely volcanoes (Mutnovsky geothermal region, Kamchatka). II. Mutnovsky volcano

Rocks structure and composition and the history of Mutnovsky volcano development which is one of the most favorable objects of geotechnical exploration according to the situation in the infrastructure of Kamchatka and high energy of modern gas-hydrothermal activity are described. Its latest volcanic activity, eruption mechanisms are discussed, the forecast of activity and morphostructural evolution of the volcano is given.

Influence of material spatial variability on slope stability in soft rock

Impacts of material spatial variability usually are not considered in traditional slope stability analyses. However, most geotechnical materials are not uniform inside a slope. The objective of the present study was to evaluate the impact of material spatial variability on slopes in soft rocks. The random field model was used to obtain the material spatial variability. The numerical analyses of slopes in soft rock mass were performed using a distinct element method based program UDEC. After that, Monte Carlo simulation, UDEC, and random field models were used together to analyze the impact of material variability and the slope stability. A series of numerical experiments were performed to understand the effect of joint spacing, joint angle, and size of scale fluctuation (δ). Also, failure types and mechanisms were synthesized and evaluated. The probability of failure became higher as the slope considered horizontal spatial variability of the material. The influence of the horizontal size of δ on slopes without joints was much higher than the slopes with joints. In addition, the slopes with joints yielded fewer failures as δ increased. The results of the analyses could be used for prevention of slope failure, future support system, and geotechnical exploration.

15 km TBM exploratory tunnel excavation in the construction Lot H33 of the Brenner Base Tunnel

AbstractThe Tulfes Pfons H33 construction contract of the Brenner Base Tunnel includes a 15 km long exploratory tunnel. The tunnel is being driven by an open gripper TBM, permitting a view of the surface of the rock mass, to achieve the best possible geological and geotechnical exploration for the deep tunnel system. Geologists and geotechnical engineers follow the TBM excavation on a daily basis and guarantee ongoing mapping and interpretation of the rock mass classification and of the TBM data. All data from the exploratory tunnel advance, the TBM data, the measured deformations and the seismic explorations as well as the findings of geological mapping are incorporated into the geotechnical longitudinal section, which serves as the basis for the tenders of the main construction contracts. In particular, discussions take place with the designer of the following contract, how the encountered fault zones and overbreaks can be passed successfully in the main tunnels. Both the improvement of the rock mass from the exploratory tunnel and ramps are considered in order to excavate the most difficult fault zones from the exploratory tunnel.

Importance of soil property sampling location in slope stability assessment

Site investigations provide characterization of soil properties, but inevitable uncertainty remains at locations that have not been examined. Only a limited scope of site investigation can be conducted due to budget and time constraints, hence there are always risks associated with design based on limited investigation information. An efficient geotechnical site investigation should involve choosing the optimal number and location of borehole sites to gain adequate information for a given cost. Using a slope as an example, this paper proposes a framework to find the best sampling location that gives the most information while minimizing the probability of making the wrong decisions. The results suggest that the slope crest appears to be the optimal location to conduct geotechnical site exploration for slope stability assessment.

From the geological prognosis to the TBM drive: Planning the main construction lots of the Brenner Base Tunnel

AbstractIt is state of the art to drive long tunnels in Alpine areas using hard rock TBMs. Mechanised tunnelling has much less flexibility than conventional excavation, so a deeper analysis of the available geological and geotechnical fundamentals is needed. In the course of planning the mechanised drives of the main tunnels on the Austrian side of the Brenner Base Tunnel, a detailed tunnelling concept was created, which deals with the project‐specific features and boundary conditions. The exploratory tunnel, which is used for geological and geotechnical exploration for the construction of the main tunnels, is currently being excavated. Through additional analyses, the geotechnical model could be verified and a reliable update of the rock parameters and the associated critical decisions has been achieved. All further specifications regarding TBM requirements, additional and auxiliary measures, support concept, bill of quantities and construction time model were based on the prognosis of system behaviour.

Thermal monitoring of railway subgrade in a region of ice-rich permafrost, Yakutia, Russia

This article presents the results of geocryological investigations conducted in the ice-rich permafrost section of the railway during the geotechnical exploration, design and construction stages, as well as prior to its permanent operation.Changes in the thermal regime of the subgrade and embankment soils have been quantified associated with the wide use of thermosyphons and insulation materials. The observations indicate rising of the permafrost table and cooling of the subgrade under high and low embankments, and active-layer deepening and ground temperature warming on the right-of-way along the railroad. Where a zero-slope fill is placed with removal of the active layer, perennial thaw bulbs have developed in the subsoil. Degradation of ice-rich permafrost is observed on the cut slopes and ditches in the cut sections. Thermosyphons on the berms in combination with Penoplex insulation have shown a cooling effect on the subgrade and permafrost table. Overhanging snow sheds on the embankment slopes have also proved to be beneficial in reducing subgrade temperatures.

A review of seismic geophysical testing in Iran for building near-surface velocity models

It has long been understood that the near-surface structure of the earth affects several aspects of civil engineering practice, particularly in seismic applications. Therefore, the implementation of a competent subsurface exploration program not only addresses the need for comprehensive site characterization but also reduces the devastating consequences of seismic activities. Typical geotechnical practice for subsurface exploration has often relied on a combination of drilling, in situ testing such as standard penetration testing and cone penetration testing, and laboratory testing of field samples. However, geophysical techniques have been developed over the years to evaluate near-surface velocity models as a proxy for subsurface stiffness in seismic applications. In this regard, seismic geophysical methods such as refraction, reflection, downhole and crosshole testing, spectral analysis of surface waves (SASW), and multichannel analysis of surface waves (MASW) have continued to receive increased attention due to their advantages over traditional geotechnical subsurface exploration techniques. This has particularly been the case in the United States and in more developed countries across Europe and Asia. However, other countries have been slower to adopt such methods, and a comprehensive review of their domestic research literature can highlight potential improvements in their standards of practice for site characterization. Considering Iran, the domestic literature on seismic near-surface geophysical methods was investigated by examining the temporal variation of several parameters of interest, including the number of published studies, methods used (e.g., active versus passive), depth of investigation, geometry of subsurface profiles developed, and the desired application. Based on this review, it was noted that more than half of the seismic geophysical studies in Iran are exclusively relying on active approaches. Of these active-based methods, more than half rely on conventional seismic refraction. Moreover, approximately 75% of studies target depths equal to 30 m or shallower, and the overwhelming majority of publications (more than 80%) develop 1D profiles. Finally, it was observed that a lag time of multiple years was often required for state-of-the-art methods to be used in Iran, particularly in the case of refraction microtremor, SASW, and MASW. This lag time also implies that these methods have not been used domestically in certain applications where other countries have grown more accustomed to using these methods. Based on results of the increased rate of usage in recent years, it is expected that seismic geophysical testing, especially surface-wave methods, will become more common in Iran and that researchers as well as practitioners will adopt these methods for near-surface site characterization and other applications.

The Anatomy of Geotechnical Risk Factors in Transportation Infrastructure Projects

Ground conditions constitute a key risk factor that can ultimately determine the successful performance of construction contracts, with the literature reporting statistics of projects which have significantly exceeded their initial budget due to geotechnical uncertainties. The study explores the nature of geotechnical risk factors in transportation infrastructure projects, which potentially lead to cost overruns. The study provides a kaleidoscopic view of the various routes to managing risks due to the ground, at the preconstruction phases of highway projects, and how a lack thereof, can culminate to determine the trend of high-cost overruns in highway projects. The study findings reveal arguments and widely contested issues in geotechnical practice, which to various degrees, can have a significant financial impact on project completion cost in highway projects. The findings uncover various error traps and gaps in practice such as the lack of deterministic costing methods that better reflect heterogeneous ground conditions; insufficiency of preliminary geotechnical exploration; poor geotechnical risk containment in contracts as well as non-deployment of multi-dimensional geotechnically bespoke contractor selection algorithm. The study submits that these gaps in practice constitute the various trajectories through which geotechnical risk can trigger inefficiency and wastage of financial resources, leading to cost overruns in transportation infrastructure projects.

Development of holistic prognosis models using exploration techniques and seismic prediction

AbstractAs part of the Brenner Base Tunnel project, the currently running Tulfes‐Pfons construction lot includes a stretch of the exploratory tunnel (ET), which has a length of 15 km and is being bored by a gripper TBM. During this tunnelling work, a diverse and broad set of exploration techniques is being used. Although it is an exploratory tunnel, the tunnel is subject to the same constraints as a performance heading. The choice of exploration techniques was made with regard of the capability to smoothly integrate them into regular tunnelling in order to not create further downtime. The exploration techniques are useful for the current ET but also to produce a forecast for the subsequent main tunnels (MT). The geological investigation is undertaken by face and peripheral mapping as well as by percussion drilling ahead of the machine. The geotechnical exploration is carried out by analysing the TBM parameters and the system behaviour, and analysing the percussion drilling. The exploration concept is completed with the geophysical reflection seismic method. All these exploration methods have different sensitivities, exploration ranges and directions, strengths and weaknesses, so they complement one another. This paper assesses the exploration techniques based on the experience until now. A case study of one fault zone is presented to show how the different exploration methods interact and contribute to a holistic prognosis model.

Improved Holistic Analysis of Rayleigh Waves for Single- and Multi-Offset Data: Joint Inversion of Rayleigh-Wave Particle Motion and Vertical- and Radial-Component Velocity Spectra

Rayleigh waves often propagate according to complex mode excitation so that the proper identification and separation of specific modes can be quite difficult or, in some cases, just impossible. Furthermore, the analysis of a single component (i.e., an inversion procedure based on just one objective function) necessarily prevents solving the problems related to the non-uniqueness of the solution. To overcome these issues and define a holistic analysis of Rayleigh waves, we implemented a procedure to acquire data that are useful to define and efficiently invert the three objective functions defined from the three following “objects”: the velocity spectra of the vertical- and radial-components and the Rayleigh-wave particle motion (RPM) frequency-offset data. Two possible implementations are presented. In the first case we consider classical multi-offset (and multi-component) data, while in a second possible approach we exploit the data recorded by a single three-component geophone at a fixed offset from the source. Given the simple field procedures, the method could be particularly useful for the unambiguous geotechnical exploration of large areas, where more complex acquisition procedures, based on the joint acquisition of Rayleigh and Love waves, would not be economically viable. After illustrating the different kinds of data acquisition and the data processing, the results of the proposed methodology are illustrated in a case study. Finally, a series of theoretical and practical aspects are discussed to clarify some issues involved in the overall procedure (data acquisition and processing).

Spatially continuous probabilistic prediction of sparsely measured ground properties constrained by ill-posed tomographic imaging considering data uncertainty and resolution

Probabilistic prediction of 2D or 3D distributions of sparsely measured borehole or direct-push logging data can contribute to solving hydrological, petroleum, or engineering exploration tasks. We use and improve a recently developed workflow constrained by ill-posed geophysical tomography to achieve 2D probabilistic predictions of geotechnical exploration target parameters that could only be measured by 1D borehole or direct-push logging. We use artificial neural networks (ANNs) to find the optimal prediction models between ensembles of equivalent geophysical tomograms and sparsely measured logging data. During the training phase of ANNs, we consider four different training strategies taking into account the logging data uncertainty and geophysical tomographic ambiguity to avoid data overfitting of the ANNs. Thus, we successfully transform the logging data uncertainty and geophysical tomographic reconstruction ambiguity as well as differences in spatial resolution of logging and tomographic models into the probabilistic 2D prediction of our target parameters in a data-driven manner, which allows application of our methodology to any combination of geophysical tomograms and hydrologic, petroleum, or engineering target parameters solely measured in boreholes. To illustrate our workflow, we use an available field data set collected at a field site south of Berlin, Germany, to characterize near-subsurface sedimentary deposits. In this example, we employ cross-borehole tomographic radar-wave velocity, P-wave velocity, and S-wave velocity models to constrain the prediction of tip resistance, sleeve friction, and dielectric permittivity as target parameters.

Geotechnical Characterization of Bukov Underground Research Facility

Bukov Underground Research Facility (Bukov URF) is designed to operate as a test site to assess the properties and behavior of the rock mass analogous to selected seven candidate sites in the Czech Republic. It is situated at a depth of about 600 m beneath Earth's surface, which corresponds with the proposed storage depth of the final locality for the national deep repository of high-level radioactive waste. Bukov URF, the construction of which has started in 2013, is situated in the southern part of the Rožná uranium deposit, about 40km NNW from Brno. The rock mass is composed of relatively monotonous rock sequences mainly represented by migmatized biotite paragneisses up to stromatic migmatites, amphibole-biotite to biotite-amphibole gneisses, and amphibolites. Based on the analysis of physical and mechanical properties, intact rocks in the studied area exhibit a high to very high strength and may be only locally affected by metasomatic alterations. The research activities focus on a complex geological and geotechnical characterization of the rock mass of interest, which is necessary for further in situ research. This paper briefly describes the main results of the current stage of geotechnical exploration and research works made there by the Institute of Geonics of the CAS. These works especially include: determination and evaluation of physical and mechanical properties of the rocks taken from the drift walls and from the boreholes during driving, calculation of rock mass quality based on selected index rock mass classification systems, determination of stress and strain state of the rock mass using the methods of hydrofracturing, Goodman Jack, strain gauge probe measurements, long-term periodical tensometric and convergence measurements, and evaluation of the effects of technical and mining-induced seismicity on the rock mass of interest.

Marine Geohazards: Review and Future Perspective

AbstractWith offshore resource exploration moving to the deep water, marine geohazards have been attracting attention from the academic and industry. Research achievements of marine geohazards were reviewed in this paper. We analyzed and discussed typical issues among marine geohazards, including coastal erosion, submarine slope failure, turbidity current and special hazards induced by gas hydrate dissociation, in terms of their definition, distribution, characteristics and case studies. Major international projects on marine geohazards headed by the United States, Europe, Japan and other international organizations are introduced as well. Three marine geohazard survey methods, including geophysical survey, geotechnical exploration and in‐situ observation, were summarized with a brief description of each approach, respectively. Especially, the history of marine geohazard researches in China is briefly reviewed, showing the disparity between China and developed countries in the study of marine geohazards narrows gradually. The potential research tendency in future was suggested.