Borehole Investigations Research Articles

Reduced T-shaped soil domain for nonlinear dynamic soil-bridge interaction analysis

The one-directional three-component wave propagation in a T-shaped soil domain (1DT-3C) is a numerical modeling technique, in a finite element scheme, to investigate dynamic soil-structure interaction (SSI) coupled with seismic site effects, under the assumption of vertical propagation of three-component seismic motion along a horizontal multilayered soil. A three-dimensional elasto-plastic model is adopted for soils, characterized using their shear modulus reduction curve.In this research, the 1DT-3C wave propagation modeling technique is proposed as an efficient tool for bridge design to take into account directly the spatial variability of seismic loading. This approach, in the preliminary phase of bridge study and design, allows the reduction of the soil domain and the easier definition of boundary conditions, using geotechnical parameters obtained with only one borehole investigation for each pier. This leads to a gain in modeling and computational time.

Combined seismic and borehole investigation of the deep granite weathering structure—Santa Gracia Reserve case in Chile

AbstractImaging the critical zone at depth, where intact bedrock transforms into regolith, is critical in understanding the interaction between geological and biological processes. We acquired a 500 m‐long near‐surface seismic profile to investigate the weathering structure in the Santa Gracia National Reserve, Chile, which is located in a granitic environment in an arid climate. Data processing comprised the combination of two seismic approaches: (1) body wave tomography and (2) multichannel analysis of surface wave (MASW) with Bayesian inversion. This allowed us to derive P‐wave and S‐wave velocity models down to 90 and 70 m depth, respectively. By calibrating the seismic results with those from an 87 m‐deep borehole that is crossed by the profile. We identified the boundaries of saprolite, weathered bedrock, and bedrock. These divisions are indicated in the seismic velocity variations and refer to weathering effects at depth. The thereby determined weathering front in the borehole location can be traced down to 30 m depth. The modelled lateral extent of the weathering front, however, cannot be described by an established weathering front model. The discrepancies suggest a more complex interaction between different aspects such as precipitation and topography in controlling the weathering front depth.

Using multivariate adaptive regression splines to develop relationship between rock quality designation and permeability

The assessment of in situ permeability of rock mass is challenging for large-scale projects such as reservoirs created by dams, where water tightness issues are of prime importance. The in situ permeability is strongly related to the frequency and distribution of discontinuities in the rock mass and quantified by rock quality designation (RQD). This paper analyzes the data of hydraulic conductivity and discontinuities sampled at different depths during the borehole investigations in the limestone and sandstone formations for the construction of hydraulic structures in Oman. Cores recovered from boreholes provide RQD data, and in situ Lugeon tests elucidate the permeability. A modern technique of multivariate adaptive regression splines (MARS) assisted in correlating permeability and RQD along with the depth. In situ permeability shows a declining trend with increasing RQD, and the depth of investigation is within 50 m. This type of relationship can be developed based on detailed initial investigations at the site where the hydraulic conductivity of discontinuous rocks is required to be delineated. The relationship can approximate the permeability by only measuring the RQD in later investigations on the same site, thus saving the time and cost of the site investigations. The applicability of the relationship developed in this study to another location requires a lithological similarity of the rock mass that can be verified through preliminary investigation at the site.

Performance of high-resolution impact and vibration sources for underground seismic exploration of clay formations at the scale of a rock laboratory

SUMMARY Low permeability, high retention capacity and self-sealing ability are advantageous characteristics that are attributed to argillaceous rocks. In contrast, other properties of clay, such as internal heterogeneities, strong attenuation and anisotropic behaviour, pose major challenges for underground exploration techniques. Although with regard to the underground storage of nuclear waste, the seismic exploration in the underground itself is of great importance to fill the gap between surface and borehole investigations. Furthermore, to prevent destruction of the host rock during exploration this demands low to non-invasive techniques. To approach these issues, a seismic survey was carried out in the Mont Terri Underground Rock Laboratory (Switzerland) using a gallery-based acquisition with an operating range up to several decametres. The seismic campaign included three-component borehole sensors and two different seismic source types (pneumatic impact and magnetostrictive vibroseis source). An executed source comparison analysed the characteristics of the different source types, for example frequency or amplitude behaviour of the generated wavefield, to assess their performance under similar conditions at the meso scale and to reveal their strengths and weaknesses in clay. Based on these findings, we performed traveltime and reflection analyses that demonstrate their potential to characterize clay formations and to map internal structures. The highest seismic velocities are found in the carbonate-rich sandy facies (vPmax = 4000 m s−1, vSmax = 2050 m s−1), slower velocities are found in the sandy facies (vPmax = 3720 m s−1, vSmax = 1840 m s−1) and the slowest velocities are found in the shaly facies (vPmax = 3220 m s−1, vSmax = 1480 m s−1). The seismic velocity anisotropy is larger within the shaly facies (AvP = 23 per cent, AvS = 32 per cent) compared to the sandy facies (AvP = 9 per cent, AvS = 12 per cent) and it is more pronounced for S-waves than P-waves. Thus, non-invasive meso-scale seismic techniques are suited to characterize the Opalinus Clay in great detail.

Identification of hydrogeological features using remote sensing and electromagnetic methods in the hard- rock formations of the Cameroon coastal plain (Central Africa): implications for water borehole location

Sustainable access to groundwater in rural areas such as the coastal plain of Cameroon (Sub-Saharan Africa) is an ongoing challenge due to the lack of knowledge on hydrogeological features favorable to the identification of potential groundwater targets. In this study, remote sensing imagery and electromagnetic surveys were used to assess the hydrogeological potential of the Ngwei locality hard-rock. Automatic extraction of lineaments from Landsat-8 images indicated 200 lineaments with a total length of 293 km corresponding to 0.6 km of lineament per square km, suggesting a median groundwater potential. The main directions are NNW-SSE, N-S and NNE-SSW while the secondary directions are NW-SE; NE-SW and E-W. Surface geophysical investigations showed an electromagnetic field of 0 to 0.57 mV. These surface and borehole investigations confirmed basement fracturing and spatial variations in weathering profiles whose aquifer structure and yields (4.4 m3/h on average) are similar to what is commonly observed in the hard rock aquifer. The correlation between borehole productivity and the nearest lineament suggests that these lineaments are not (at least not all) surface traces of regional discontinuities that may act as major groundwater flow paths. This implies that the productivity of the Ngwei aquifers appears to be dependent on the fissured/fractured horizon, so exploration should be based on a contextual rather than general approach.Analysis of the consistency of the results with the field data allowed to propose a preliminary electromagnetic log model and also shows the value of using this approach to assess the availability of potential groundwater zones in hard rock areas. However, the methods used should be supported by further investigations to allow a better understanding of the hydrogeological characteristics of this part of the Central African basement so that no one is left behind in the achievement of the SDGs.

Two-dimensional numerical simulation of spontaneous potential logging data with account to clay content of a reservoir by finite element method

Spontaneous polarization potential (SP) logging remains one of the most widely used geophysical methods of borehole investigation. However, for a long time its interpretation was based on empirical dependences and analytical solutions in simplified formulations. At present the development of the method is associated with the development of new approaches to numerical modeling and quantitative interpretation of SP logging data. Application of numerical algorithms makes it possible to considerably increase information content and resolution of SP method. Nevertheless, most of the currently proposed approaches rely on a simplified description of SP signal formation, which may lead to errors in data interpretation for complex reservoir intervals. In this work, we propose an algorithm for numerical simulation of SP logging data as applied to the study of clayed fluid-saturated reservoirs. The physical and mathematical model of SP signal formation in terms of coupled fluxes for the case of electrochemical SP source is considered. The software realization of the algorithm includes a two-dimensional numerical simulation of SP signals based on the application of the finite element method in the axially symmetric model of the geological medium. The character of SP signals for reservoirs of different thickness at four values of the reservoir water saturation coefficient is studied, as well as the dependence of the shape and amplitude of the SP anomaly in a water- and oil-saturated clayed reservoir on the content and type of clay mineral. The obtained results, aimed at the development of the SP method, improve the quality of SP diagrams interpretation for the study of clayed reservoirs.

Construction geological logging of the Thames Tideway Tunnel beneath central London: unearthing the ground truth

Large-scale underground structures excavated during the construction of the Thames Tideway Tunnel have facilitated observations of the in situ geology and revealed sedimentary characteristics that were not fully evident in disturbed samples from ground investigation boreholes or laboratory tests. These have led to significant improvements in the understanding of groundmass behaviour of several strata within the London Basin geological sequence that are not easily studied by intrusive ground investigations, especially those involving sand channels and the ‘Pebble Bed’ within the Lambeth Group deposits. Further validation of the ground model and geology projected over the scheme during the preconstruction design has been gained from logging the geology within deep shafts, open-face connection tunnels and the main 8.8 m-outer-diameter tunnel from behind the tunnel-boring machine cutterhead. It is recommended that an archive of field logs, as obtained during construction, be established to augment archives of borehole logs. Thematic collection: This article is part of the Geology of London and its implications for ground engineering collection available at: https://www.lyellcollection.org/cc/london-basin

Spatial and Temporal Constraints on the Composition of Microbial Communities in Subsurface Boreholes of the Edgar Experimental Mine.

ABSTRACTThe deep biosphere hosts uniquely adapted microorganisms overcoming geochemical extremes at significant depths within the crust of the Earth. Attention is required to understand the near subsurface and its continuity with surface systems, where numerous novel microbial members with unique physiological modifications remain to be identified. This surface-subsurface relationship raises key questions about networking of surface hydrology, geochemistry affecting near-subsurface microbial composition, and resiliency of subsurface ecosystems. Here, we apply molecular and geochemical approaches to determine temporal microbial composition and environmental conditions of filtered borehole fluid from the Edgar Experimental Mine (∼150 m below the surface) in Idaho Springs, CO. Samples were collected over a 4-year collection period from expandable packers deployed to accumulate fluid in previously drilled boreholes located centimeters to meters apart, revealing temporal evolution of borehole microbiology. Meteoric groundwater feeding boreholes demonstrated variable recharge rates likely due to a complex and undefined fracture system within the host rock. 16S rRNA gene analysis determined that unique microbial communities occupy the four boreholes examined. Two boreholes yielded sequences revealing the presence of Desulfosporosinus, Candidatus Nitrotoga, and Chelatococcus associated with endemic subsurface communities. Two other boreholes presented sequences related to nonsubsurface-originating microbiota. High concentration of sulfate along with detected sulfur reducing and oxidizing microorganisms suggests that sulfur related metabolic strategies are prominent within these near-subsurface boreholes. Overall, results indicate that microbial community composition in the near-subsurface is highly dynamic at very fine spatial scales (<20 cm) within fluid-rock equilibrated boreholes, which additionally supports the role of a relationship for surface geochemical processes infiltrating and influencing subsurface environments.IMPORTANCE The Edgar Experimental Mine, Idaho Springs, CO, provides inexpensive and open access to borehole investigations for subsurface microbiology studies. Understanding how microbial processes in the near subsurface are connected to surface hydrological influences is lacking. Investigating microbial communities of subsurface mine boreholes provides evidence of how geochemical processes are linked to biogeochemical processes within each borehole and the geochemical connectedness and mobility of surface influences. This study details microbial community composition and fluid geochemistry over spatial and temporal scales from boreholes within the Edgar Mine. These findings are relevant to biogeochemistry of near-surface mines, caves, and other voids across planetary terrestrial systems. In addition, this work can lead to understanding how microbial communities relate to both fluid-rock equilibration, and geochemical influences may enhance our understanding of subsurface molecular biological tools that aid mining economic practices to reflect biological signals for lucrative veins in the near subsurface.

Identification of buried historical mineshaft using ground-penetrating radar

Buried historical mineshafts constitute significant sinkhole hazards and sources of geotechnical risks. The locations of buried mineshafts on old mining maps are prone to inaccuracies. An efficient way to limit these inaccuracies is to use geophysical methods. However, their effectiveness strongly depends on the local survey conditions.The aim of the study was to identify the buried 14th century Wielki mineshaft in Bochnia Salt Mine, a UNESCO Worldwide Heritage Site, Poland. The need to locate this shaft was due to the following reasons. Firstly, the Bochnia Salt Mine had difficulties with water flowing into the workings from the supposed location of the Wielki mineshaft. The shaft area was one of the most waterlogged in the salt mine's terrain. An urgent task was to determine the shaft's exact location to implement a waterproof barrier to protect the historic mine workings. Secondly, the modernisation of the market square in Bochnia required clarification of the location of the Wielki mineshaft and checking as to whether it posed a sinkhole hazard to the terrain surface. Another important reason for locating the medieval shaft was its archaeological value.A ground surface and borehole ground-penetrating radar (GPR) study and geological-engineering recognition using boreholes were employed to indicate the location of the Wielki shaft. The anthropogenic layer of heterogeneous material and the urbanised site resulted in challenges with regard to detecting evident georadar anomalies. Several dozen intersecting GPR profiles were gathered in the research area using 250 MHz and 100 MHz antennae. The initial surface GPR results, indicative of the GPR anomaly, were consolidated by cored borehole investigation and a borehole GPR study. In particular, the presence of a void, loosened zones, and wooden fragments of the shaft lining was confirmed in the inclined control borehole. Following our classification of typical causes of the occurrence of sinkholes over buried mineshafts, the consolidation of backfill material in a mineshaft was determined as the cause of the sinkhole originated above the Wielki shaft (type B sinkhole). Destruction of the shaft's wooden cap may result in the occurrence of a sinkhole on the ground surface. Therefore, the void was backfilled and a hydraulic barrier was consequently made to stop the seepage of water into the Bochnia Salt Mine's historic workings.This case study demonstrates that surface and borehole GPR surveying integrated with borehole data offers the possibility of obtaining the high-resolution data needed to accurately locate an old buried mineshaft in an urbanised area. The GPR anomaly was indirectly detected on the basis of the deflection of the boundary between the natural ground and an anthropogenic layer with sufficient contrast in their electromagnetic properties. This approach can be useful wherever the georadar penetration range is limited by high attenuation and dispersiveness of the anthropogenic layer.

Study on the Seismic Effect of the Interbedded Soil Layer in the Yinchuan Alluvial Plain

This paper presents a numerical analysis of two types of representative site profiles in the Yinchuan Plain under earthquake loading. The analyzed soil profiles, based on borehole investigations performed over the years, are used to explore the seismic response of the sites in this area. In total, eleven stratified soil models are used in this study, which can be grouped into two categories: a single interbedded soil model and multiple interbedded soil model. A one-dimensional equivalent linearization method is applied to evaluate the seismic response of different soil models under four exceeding probabilities in terms of peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), and spectral acceleration (Sa). The results show that the significant amplification effect of PGA occurs in rare and extremely rare earthquakes, with an amplification ratio of 1.4∼1.7 when the single silty clay layer is located at the model ground. In this scenario, the spectral acceleration is amplified at a period of approximately 1.0 s. For the multilayered soil cases, the amplification effect tends to decrease, whereas the characteristic periods increase with increasing numbers of soil layers and the ground acceleration is deamplified under a high motion intensity when the number of soil layers is ≥ 5. This study, to a certain degree, has reference value for seismic microzonation in this area.

The highest potential transmissivities of fractures in fault zones: Reference values based on laboratory and in situ hydro-mechanical experimental data

The transmissivity of a fracture can be related to fracture roughness (JRC0), initial aperture (E0), effective normal stress (σ'n), and tensile strength (σt) of the intact rock, based on the Barton–Bandis model and their data, and the transmissivity (or E0) can increase by shear-induced dilation. Previous studies revealed that the transmissivities of fractures in fault zones, detected as flow anomalies (highly transmissive zones) during borehole investigations at six sites, decrease uniformly with an increasing effective mean stress normalized to σt. If this uniform change in transmissivity is explained by σ'n-dependent fracture-normal displacement following the Barton–Bandis model, those transmissivities represent the upper limit of transmissivities of fractures in fault zones that can increase by shear-induced dilation. To verify this possibility, the E0 of fractures was estimated using those transmissivities, σt, and possible JRC0 and σ'n. Then, using this estimated E0, the changes in transmissivity were simulated, varying σ'n. The results reproduced very well the observed uniform change in transmissivity. The estimated values of E0 are tens of micrometers to a few millimeters, which can occur by slight shear displacements (e.g., 0.05–2.00 mm) during shear-induced dilation, easily achievable in fault zones. Thus, the requirements for the highest transmissivities are slight shear displacements and no/limited fracture-sealing rather than large shear displacements. Transmissivities in fault zone fractures that have already reached the highest transmissivities do not change significantly by shear displacement, while the transmissivities of fractures sealed by mineral filling can increase by orders of magnitude, as confirmed by recent fault-stimulation-experiments.

Water control for a rock-soil interface - infrastructure at a contaminated site

The conceptual model of the rock-soil f(and future shaft) interface was confirmed (so far not rejected) using data from investigation boreholes. The location of a depression in rock (a likely deformation zone) was indicated and confirmed using borehole data. Wave-washed deposits (upper part of the stratigraphy) and a lower water-bearing strata (soil) coinciding with the depression are key water-bearing features in soil. The likely deformation zone is expected to be a key water-bearing feature in rock. Grouting design (curtain-and blanket grouting) and sealing of soil (jet-grouting and sheet-pile walls) focus on sealing these features. The wells (infiltration) that are planned between the shaft and a contaminated site may, if needed, further reduce the effect of the construction on hydraulic head and flow. Changes that are of interest since they may also influence the mobility of a contamination. A low grouting pressure is used in rock adapting to a shallow depth (curtain grouting) and a possible horizontal connectivity. The steps of the observational method, as described by Peck (1969), were found very useful. Its focus on “the general nature, pattern and properties” and “a working hypothesis of behaviour” is of particular interest, highlighting the understanding of the system at hand.

Multidisciplinary Approaches for Assessing a High Temperature Borehole Thermal Energy Storage Facility at Linköping, Sweden

Assessing the optimal placement and design of a large-scale high temperature energy storage system in crystalline bedrock is a challenging task. This study applies and evaluates various methods and strategies for pre-site investigation for a potential high temperature borehole thermal energy storage (HT-BTES) system at Linköping in Sweden. The storage is required to shift approximately 70 GWh of excess heat generated from a waste incineration plant during the summer to the winter season. Ideally, the site for the HT-BTES system should be able to accommodate up to 1400 wells to 300 m depth. The presence of major fracture zones, high groundwater flow, anisotropic thermal properties, and thick Quaternary overburden are all factors that play an important role in the performance of an HT-BTES system. Inadequate input data to the modeling and design increases the risk of unsatisfactory performance, unwanted thermal impact on the surroundings, and suboptimal placement of the HT-BTES system, especially in a complex crystalline bedrock setting. Hence, it is crucial that the subsurface geological conditions and associated thermal properties are suitably characterized as part of pre-investigation work. In this study, we utilize a range of methods for pre-site investigation in the greater Distorp area, in the vicinity of Linköping. Ground geophysical methods, including magnetic and Very Low-Frequency (VLF) measurements, are collected across the study area together with outcrop observations and lab analysis on rock samples. Borehole investigations are conducted, including Thermal Response Test (TRT) and Distributed Thermal Response Test (DTRT) measurements, as well as geophysical wireline logging. Drone-based photogrammetry is also applied to characterize the fracture distribution and orientation in outcrops. In the case of the Distorp site, these methods have proven to give useful information to optimize the placement of the HT-BTES system and to inform design and modeling work. Furthermore, many of the methods applied in the study have proven to require only a fraction of the resources required to drill a single well, and hence, can be considered relatively efficient.

Leachate migration investigation at an unlined landfill located in granite region using borehole groundwater TDS profiles

Special hydrogeological properties of granite regions control leachate migration in municipal solid waste (MSW) unlined landfills there. This study aimed to investigate leachate migration at an unlined landfill located in a granite region and explore an in-situ borehole groundwater TDS-profile method (BGTM) for identifying vertical distribution of leachate plume at landfill sites in granite regions. On basis of detailed site investigation using multiple methods (e.g., borehole investigation, water quality monitoring, and rock packer tests), hydrogeological model of the surveyed MSW landfill was established, and horizontal distribution of four contaminants including chemical oxygen demand, ammoniacal nitrogen showed that leachate plume could reach over 200 m away from downstream boundary of the source landfill. BGTM was demonstrated to be able to identify boundary of leachate plume under a field average influx >1.0 × 10−7 cm/s and a hydraulic conductivity of the evaluated layers >5.0 × 10−5 cm/s. Based on the site investigation, granite joints were found to be the major leachate migration channels in the lateral slope of the granite valley, and highly permeable layers such as alluvium were identified as the major leachate migration channels in the valley outlet. Meanwhile, a two-piece function was fitted between groundwater total dissolved solid (TDS) and electrical conductivity (EC) in the landfill site, and EC = 500 μS/cm was the limit between the two intervals.

Geophysical and borehole investigations of subsurface hazardous karsts in Ar-Riyadh city, Kingdom of Saudi Arabia

Geophysical and borehole investigations of subsurface hazardous karsts in Ar-Riyadh city, Kingdom of Saudi Arabia

Mechanism analysis and partition characteristics of a recent highway landslide in Southwest China based on a 3D multi-point deformation monitoring system

An increasing number of landslides are occurring during the construction of highways in mountainous areas all over the world. A recent highway landslide located in the mountainous region of Southwest China is taken as a representative example to carry out the initiation mechanism and deformation characteristics analysis, and study the intelligent partitioning method in this paper. The geological conditions of the landslide are obtained through detailed geological surveys and investigation. A three-dimensional (3D) monitoring network with a total of 72 multi-points, including 53 surface displacement monitoring points and 19 deep displacement monitoring holes, is established to examine the spatial deformation characteristics of the landslide for nearly 25 months. The monitoring results of the surface displacement show that the dynamic deformation of the landslide can be divided into three stages, namely initial deformation stage, accelerated deformation stage, and stabilization stage. Based on the strata distribution obtained by the borehole investigation and the results of deep displacement monitoring, the depth of the slip surface can be reliably determined. The smart contract method in blockchain technology combined with the multi-point monitoring dataset is novelty applied to realize the intelligent automatic partition of the highway landslide without any human involvement. This method can provide the basis for further independent analysis of different landslide zones. According to the investigation and analysis, the initiation mechanism for the highway landslides is attributed to both internal poor geological conditions and external intense precipitation and engineering excavation.

Investigation of Old Exploration Boreholes in the Lublin Basin with Regard to Potential Rotary-Percussion Drilling of Shale Gas Wells

The rotary-percussion drilling method is a prospective way to decrease drilling costs. It is obvious, based on literature analyses and finished geothermal drilling, that the Lublin Basin can be perceived as the one where rotary-percussion drilling can be used to drill an overburden of shale rocks. The paper explained the geology of the Lublin Basin, its’ geological structures, and the possibility of the use of drilling with a down-the-hole hammer, which could significantly decrease the cost of the whole shale gas drilling investment. Data collected from the wells drilled in the Lublin Basin were compared and analyzed to determine the viability of rotary-percussion drilling. Provided analyses showed that using the rotary-percussion drilling method in the Lublin Basin had a greater possibility of application than in other Polish shale basins (Baltic and Podlasie).

A geotechnical stratigraphy for the shallow subsurface in the Southern Central Graben, North Sea

The Integration of conventional 3D seismic data with high-resolution 2D seismic data and cone penetration test (CPT) data from geotechnical jack-up foundation reports has enabled a new late Quaternary geotechnical stratigraphy for the Southern Danish Central Graben area in the North Sea. The shallow subsurface has been subdivided into geotechnical units based on seismic appearance and soil behaviour type. The lateral thickness and geotechnical property variations have been mapped and associated with the existing stratigraphies from adjacent areas in the German and British sectors. The geotechnical variations have also been related to geomorphological features in the subsurface that are a result of the changing glacial conditions over the last 120.000 years. Particularly, buried valleys produce unpredictable geotechnical conditions that require additional evaluation and possibly borehole investigations as well as CPTs. The study synthesizes data from multiple geotechnical surveys and extrapolates the local knowledge from the different sites, providing a better regional understanding of the geology and the geotechnical behaviour of the shallow subsurface. • A geotechnical stratigraphy based on seismics and CPT data. • Correlation of seismic facies and geotechnical property distributions. • Regional stratigraphic input to improve risk assessment in offshore construction. • Geotechnical data improves geological evolution models.

Geophysical research and geotechnical database construction for selecting design parameters of mining systems

A passport to success in mineral mining is the detailed geomechanical information on enclosing rock mass and structure of a mineral deposit. These data are used as a framework for the rock mass stability estimation. These data are taken into account in critical decision-making on mine design, which finally determines the mine safety and performance. The authors review the current methods of acquisition of geotechnical data at the stage of geological exploration. The structural model is constructed for Shiraldzhin gold deposit in Kyrgyzstan. The structural modeling used the data of geophysical measurements in 6 boreholes. It is shown that construction of a geotechnical database helps design future parameters of a mining system. Geophysical borehole investigations have an advantage over the conventional coring techniques in terms of cost and accuracy. The geophysical borehole measurements using a borehole image scanner requires maintenance of borehole parameters: diameter not less than HQ; angle not less 55°; mouth casing down to bedding rocks. Finally, the major requirement is scanning to be accomplished immediately after drilling (within one day depending on rock stability).

Stochastic nonlinear ground response analysis via a case study site in Shiraz city

This study attempts to investigate the influence of the dynamic soil properties uncertainties on ground response analysis via a case study site. For this purpose, nonlinear time-domain ground response analysis and uncertainties in soil parameters are coupled simultaneously using a coded program in MATLAB. To take full advantage of the real data, two investigation boreholes are drilled in the site. The analysis is performed deterministically and then extended to the stochastic context in order to take into consideration the variability of Plastic Index, shear wave velocity, and unit weight of the soil. In a part of this study, the capability of the three different methods for predicting the stochastic fundamental period of the site including modal analysis, approximate method, and nonlinear method, is investigated. To achieve the advantage of the stochastic analysis, the maximum Coefficient of Variation (COV) of the peak ground motion parameters, fundamental period, response spectrum, and amplification factor are calculated. The results demonstrate that the heterogeneity of the soil parameters has a significant effect on the variation of the surface Peak Ground Displacement (PGD). Among the other stochastic responses, the fundamental period has received the least effect from soil parameters’ uncertainty.