Results Of Site Investigation Research Articles

Feature analysis of precipitation-induced subgrade defects on a high-speed rail ballasted track using multiple track inspection data: A case study

Heavy rainfall has posed a great challenge to the service performance of high-speed rail (HSR) substructure, resulting in a reduction in the ride quality and safety of high-speed trains. To carry out proper repair work for the substructure, it is imperative to realize efficient identification of precipitation-induced subgrade defects. To this end, this paper aims to extract the features of typical precipitation-induced subgrade defects from the multiple track inspection data to provide a basis for defect identification. Firstly, the geotechnical site investigation including Ground Penetrating Radar (GPR) detection, moisture content test, and dynamic cone penetration (DCP) test of a typical defective spot is performed to determine the condition of the subgrade after heavy rainfall; then, the analysis methods of track inspection data are introduced; finally, the track geometry data and carbody acceleration data of four typical defective sections are analyzed, and the time-domain, frequency-domain and discrete wavelet transform (DWT)-based features which are highly correlated with the precipitation-induced subgrade defects are extracted. The results show that the feature indexes extracted from track surface irregularity and carbody vertical acceleration increase significantly after heavy rainfall; the long wavelength components (8 m and above) of both track irregularity and carbody vibration are more sensitive to the subgrade defects, which is reflected by the sharp increase of the DWT-based features at some levels corresponding to long wavelength ranges. The results of defect feature extraction based on the track inspection data agree well with the geotechnical site investigation results, which demonstrate the feasibility of utilizing multiple track inspection data to identify the typical precipitation-induced subgrade defects.

Sedimentation conditions and clast transport during the formation of sedimentary paleobasins in the north of Irkutsk Oblast and river network formation

Background. Changes in the composition of clastic material reflect changes in both the paleogeographic environment and clast transport paths. In turn, this indicates changes in the conditions of regional development. The research relevance is determined by multidirectionality of Earth sciences, such as paleogeography, neotectonics, stratigraphy, hydrology, relief formation, etc.Aim. To establish the genesis of river valleys and bench complexes in the northern areas of the Irkutsk Oblast.Materials and methods. The clastic material of the Upper Paleozoic-Mesozoic sedimentary deposits in the northern areas of the Irkutsk Oblast was studied. The work is aimed at reconstructing the contours of sedimentary paleobasins of the Carboniferous, Permian, and Jurassic ages and the conditions of sedimentary strata formation. The results of site investigation and drilling works carried out in the 1960s and 1970s were interpreted from the standpoint of modern information.Results. The nature of river network formation and clast transport processes was determined. The direction and sources of clast transport were identified, along with the conditions of re-deposition of clastic material at different stages of the geological development of the area under study.Conclusions. The modern river network in the northern areas of the Irkutsk Oblast is based on the valleys formed under the action of catastrophic glacial water discharge flows.

Numerical Assessment on Unloading Disturbance and Gas Extraction in Remote Distance Protective Layer Mining

Protective layer mining could not only significantly alter geostress but also increase the permeability of protected layer, which is beneficial for the coal gas extraction rate and ensures coal mining safety. However, due to unique geologic conditions, remote distance protective layer mining has its own characteristics. To investigate characteristic changes caused by remote distance protective layer mining, a suitable mathematical model that considered disturbance of unloading mining and solid-gas coupling effects during gas extraction was developed. The established mathematical model was implemented by combining FLAC3D and COMSOL programs to study characteristic changes during remote distance protective layer mining of Chajiaotan coal mine. Numerical simulation results of unloading disturbance mining indicated that the protected layer would experience a process of stress loading, stress unloading, stress recovery, and stress stability as the working face of protective layer advanced; unloading disturbance has a greater influence on coal permeability than gas pressure; gas extraction measure should be further adopted to decrease gas pressure. Numerical comparisons of gas pressure distribution in the original protected layer and unloading protected layer revealed that gas extraction after unloading disturbance can reduce gas pressure more effectively, and appropriate borehole spacings in the fully pressure-relief and nonfully pressure-relief zones are 30 m and 5 m, respectively. The layout of field boreholes for gas extraction was designed according to numerical results. The results of site investigation showed that numerical simulation results of relative expansion deformation and gas extraction radii agree well with the results of site observation, demonstrating reliability of the mathematical model and its implementation. The proposed mathematical model is promising for assessing unloading disturbance and gas extraction in remote distance protective layer mining.

Rockhead profile simulation using an improved generation method of conditional random field

Rockhead profile is an important part of geological profiles and can have significant impacts on some geotechnical engineering practice, and thus, it is necessary to establish a useful method to reverse the rockhead profile using site investigation results. As a general method to reflect the spatial distribution of geo-material properties based on field measurements, the conditional random field (CRF) was improved in this paper to simulate rockhead profiles. Besides, in geotechnical engineering practice, measurements are generally limited due to the limitations of budget and time so that the estimation of the mean value can have uncertainty to some extent. As the Bayesian theory can effectively combine the measurements and prior information to deal with uncertainty, CRF was implemented with the aid of the Bayesian framework in this study. More importantly, this simulation procedure is achieved as an analytical solution to avoid the time-consuming sampling work. The results show that the proposed method can provide a reasonable estimation about the rockhead depth at various locations against measurement data and as a result, the subjectivity in determining prior mean can be minimized. Finally, both the measurement data and selection of hyper-parameters in the proposed method can affect the simulated rockhead profiles, while the influence of the latter is less significant than that of the former.

Seismic Soil Characterization to Estimate Site Effects Induced by Near-Fault Earthquakes: The Case Study of Pizzoli (Central Italy) during the Mw 6.7 2 February 1703, Earthquake

Many of the urban settlements in Central Italy are placed nearby active faults and, consequently, the ground motion evaluation and seismic site effects under near-fault earthquakes are noteworthy issues to be investigated. This paper presents the results of site investigations, the seismic site characterization, and the local seismic response for assessing the effects induced by the Mw 6.7 2 February 1703, near-fault earthquake at the Madonna delle Fornaci site (Pizzoli, Central Italy) in which notable ground failure phenomena were observed, as witnessed by several coeval sources. Even though recent papers described these phenomena, the geological characteristics of the site and the failure mechanism have never been assessed through in-situ investigations and numerical modeling. Within a project concerning the assessment of soil liquefaction potential and co-seismic ground failure, deep and shallow continuous core drilling, geophysical investigations and in-hole tests have been carried out. Subsequently, the geotechnical model has been defined and the numerical quantification of the different hypotheses of failure mechanisms has been evaluated. Analyses showed that liquefaction did not occur, and the excess pore water pressure induced by the shaking was not the source of the ground failure. Therefore, it was hypothesized that the sinkhole was likely caused by earthquake-induced gas eruption.

Pioneering groundwater contamination investigation, research, and in situ treatment.

The 1972 paper by Professor Jack McKee of the California Institute of Technology, consulting engineer Finley Laverty and Raymond Hertzel of the California Regional Water Quality Control Board-Los Angeles (McKee et al., 1972) was an early, important contribution to the understanding of groundwater contamination with organic liquids and to the integrated use of field, laboratory, and modeling studies to develop remediation approaches. The work presented in the paper was ahead of the curve and helped provide the foundation for the intense research, development, and education in investigation and remediation of groundwater contamination problems that began around 1980 and lasted for two decades. Reading the paper in the current context of more than 40years of research and field experience provides perspective on how little was known in 1972 about groundwater contamination and how to address it, and how well-formulated and forward-looking was the work of McKee et al. PRACTITIONER POINTS: McKee et al. (1972) was an early, important contribution to the understanding of groundwater contamination with organic liquids and to the integrated use of field, laboratory and modeling studies to develop remediation approaches. McKee et al. present the results of site investigation and remediation planning studies for a large-scale groundwater contamination site in the Los Angeles-Glendale, California area. Four specific remediation goals were established, and a comprehensive program of site investigation, research, and modeling was developed to support the achievement of the remediation goals. The comprehensive site investigation and remedial planning involving field, laboratory, and modeling studies described by McKee et al. was a forerunner of what came into standard contaminated site remediation practice in the 1980s and 1990s.

Selection of standard penetration test number for geotechnical investigation of a vertical cross section considering spatial variability and correlation in soil properties

The standard penetration test (SPT) is a widely used in situ test for characterizing variation of subsurface soil properties, and results of site investigation are usually simplified as a two-dimensional (2D) vertical cross section for subsequent geotechnical design and construction. Current geotechnical design codes and guidelines only provide general recommendations for selection of an appropriate number of in situ tests (e.g., SPT) (e.g., the greater variability of subsurface conditions, the larger number of SPTs required to obtain sufficient underground information). No quantitative or rational method is available for selecting the appropriate number of SPTs considering spatial variability and correlation in subsurface conditions. A comprehensive parametric study is carried out in this study to investigate the influence of spatial variability in subsurface conditions on the minimum SPT number needed for satisfying an accuracy requirement of site investigation. Random field is adopted to model spatial variation and correlation in soil properties in typical site conditions, and 2D Bayesian compressive sampling is used to interpolate sparse SPT data. Based on the parametric study results, a statistical chart is developed for geotechnical engineers to conveniently select an appropriate number of SPTs in a vertical cross section. Real SPT data from New Zealand are used to illustrate and validate the proposed method.

Seismic Hazard Vulnerability of Bengkulu City, Indonesia, Based on Deterministic Seismic Hazard Analysis

Bengkulu City is one of cities in Indonesia, which is located on the west coastline of Sumatra. Within last two decades, Bengkulu City had undergone at least two large earthquakes with magnitudes ≥ Mw 7.0. This paper presents a study of deterministic seismic hazard for Bengkulu City. The hazard analysis is initiated by determining the controlling earthquake. Site investigation results are also studied for seismic ground response analysis. Analysis is performed by propagating seismic wave to investigate seismic behaviour during earthquake. Three parameters including peak ground acceleration, spectral acceleration at 0.2 s (SA at 0.2 s), and spectral acceleration at 1 s (SA at 1 s) are analysed to generate seismic hazard maps. In general, this study could help people to understand seismic hazard in Bengkulu City. The results also could recommend local engineers to consider earthquake in structural design and spatial plan in Bengkulu City.

Site Investigation Results and Verification of Liquefaction Countermeasure Effect by Groundwater Lowering Method at Tsukiji in Amagasaki City

Site Investigation Results and Verification of Liquefaction Countermeasure Effect by Groundwater Lowering Method at Tsukiji in Amagasaki City

Statistical charts for determining sample size at various levels of accuracy and confidence in geotechnical site investigation

Site investigation is indispensable in geotechnical practice, but only a small portion of the soil affected by the intended geotechnical construction is examined and/or tested in the laboratory or in situ, leading to significant uncertainties in site investigation results. The uncertainty in the site investigation results depends greatly on the number of specimens tested (i.e. sample size) during site investigation. In many other areas that involve sampling, such as polls, surveys and quality control, sample sizes are often determined using statistical charts, based on the target levels of accuracy and confidence. However, conventional statistical charts, which only deal with independent data, are seldom used in geotechnical site investigation, because geotechnical properties are usually spatially correlated. No statistical chart with consideration of spatial correlation is available for determining sample sizes in geotechnical site investigation. Existing geotechnical design codes around the world (e.g. Eurocode 7) only provide conceptual principles on sample size determination. This study develops statistical charts for determination of sample size at different levels of both accuracy and confidence for geotechnical site investigation. Real cone penetration test data and real laboratory test data are used to illustrate application of the proposed statistical charts, and the charts are shown to perform well.

Two-Dimensional Random Field Conditioned by CPT Data: Case Study

The presented geotechnical random field (GRF) algorithm is utilized to realize the soil inherent variability based on in situ site investigation results. This paper aims at investigating the effect of cone penetration test (CPT) borehole arrangements in horizontal plane on slope stability reliability analysis considering stochastic fields of soil design parameters via the conventional stationary along with the non-stationary random field adopted in the GRF approach. An advantage of the GRF algorithm is that it yields conservative results in comparison to the conventional stationary random field theory; therefore, using non-stationary random field underestimates slope stability reliability. The current study tried to highlight the importance of the availability of in situ profiles of soil strength parameters when stability analysis of geotechnical structures is concerned. Slope stability was chosen to interpret the role of the CPT profiles in the adjacent site in determining the factor of safety of the slope against shear failure. Furthermore, the results of the case under study showed that when the geometric dimensions of the slope are too small compared to the horizontal correlation length, more CPT borehole data availability leads only to very slightly conservative results in comparison to the case with single available CPT profile.

Engineering geology and ground collapse mechanism in the Chengchao Iron-ore Mine in China

The engineering geological and hydrogeological conditions in the eastern mining area of the Chengchao Iron Mine are analyzed in detail. The results are combined with the results of site investigations and in situ monitoring data, allowing the characteristics of the ground-surface collapse events to be summarized. The mechanism by which ground-surface collapse is induced by underground orebody extraction or de-watering activity was then investigated. The results show that the ground-surface in the mining areas experienced three collapse processes: karst collapse, mixed collapse, and mining-induced collapse. Karst-collapse sinkholes were found during the construction stage of the mine and are generally formed in the marble part of the marble–granite contact zone. These sinkholes show a ‘bead-on-a-string’ distribution, and lines connecting their centers are consistent with the strike of the marble. Such sinkholes are mainly formed due to changes in the dynamic conditions of groundwater caused by de-watering activity. Furthermore, the development level of the collapse mainly depends on the location and scale of the karst caves within the marble. Mixed collapse occurs in the initial mining stage and mainly results from the combined effect of underground orebody excavation and de-watering activity. Mining-induced ground-surface collapse pits mostly develop in the diorite and hornstone and generally show a zonal distribution along the strike of the orebodies from east to west. Mining-induced collapse occurs in the form of chimney caving. First, a caved pipe is formed where the rock masses above the caved zone are highly fractured. Then, the rock masses around the caved pipe gradually cave, and finally a large caved-zone is formed above the mined-out area. Mixed collapse is of particular interest as it is a peculiar type of subsidence involving the superposition of collapse processes related to both mining and karst cavities, and it can provide some instructive insight into the collapsing behavior of the ground-surface.

Evaluation of railway trackbed moduli using the rail falling weight test method and its backcalculation model

A new falling weight test method based on the direct impact on the rail was studied and a backcalculation model was developed to estimate the moduli of the railway substructure layers. The model is three-dimensional, dynamic, and considers the superstructures. After the preliminary studies on the impact system and measurement setup on a test track, a case study was performed on a railway station track. The data were recorded using a series of linear variable differential transformers, geophones, and accelerometers during the proposed falling weight test on the rail. To establish the soil profile and better understanding of the site, geotechnical and geophysical investigation of the soil was done using in situ and conventional laboratory tests. The studies show that the rail falling weight test is feasible and leads to reasonable results. Verification of the backcalculation model with the ABAQUS finite element simulation and comparison of the backcalculated moduli with the results of site investigations show that the function of the backcalculation model is satisfactory.

The effect of embedded gypsum streaks on the dissolution of dam foundation: a case study in Iran

Evaporative rocks are known to have a high susceptibility to dissolution in fresh water. Substantial evidence all over the world has shown that the dissolution of evaporative rocks in the foundations of dams and basins can lead to unfortunate disasters. In a basin located in Iran, owing to dissolution of evaporative rock in the foundation on the south side, some hazardous events, such as unexpected subsidence, ground collapse, and water escape from the reservoir, have been reported. Comprehensive geological and geophysical surveys along with detailed geotechnical investigations were performed in order to assess the reasons. By analyzing the site investigation results, it is recognized that even though the foundation of the basin is composed of impervious marl layer, the dissolution of thin streaks of gypsum embedded inside the marl layer provides interconnected paths for the flow of water into the lower depths of the foundation in order to reach to halite layer located inside the marl. The geophysical survey results indicate that the zone with defects is limited to the specific area of the basin where the halite layer is located relatively near the ground surface. However, if the reservoir is filled completely again, the dissolution front may advance to other zones of the basin, and more area of the basin ground may be affected by subsidence and other relevant phenomena.

Site-specific partially nonergodic PSHA for a hard-rock critical site in southern France: adjustment of ground motion prediction equations and sensitivity analysis

Modern probabilistic seismic hazard assessment (PSHA) focuses on the separation and different treatment of epistemic and aleatory uncertainties. Recent site-specific PSHA studies have pointed out that, if the site response and its epistemic uncertainties can be appropriately considered by adjustments to median estimates from ground motion prediction equations (GMPEs), the aleatory variability (sigma) of the GMPEs can be replaced by the single-station sigma thus partially relaxing the ergodic assumption employed in the PSHA. The site-specific partially nonergodic approach, correctly applied, provides a more accurate representation of the seismic hazard at a specific site and a more rigorous treatment of uncertainties. This paper presents the strategy followed to apply this relatively recent approach to a critical infrastructure in Southern France located on hard-rock site conditions (Vs30 ≈ 2000 m/s). The target site conditions are defined in terms of shear-wave velocity (Vs) profiles and high-frequency attenuation (κ0) based on the results of site investigations and on the exploitation of earthquake records at seismic stations in the target site area. The host-to-target Vs-κ0 adjustment of median estimates for the selected GMPEs is performed by using the inverse random vibration theory approach (Al Atik et al. in Bull Seismol Soc Am 104:336–346, 2014) considering epistemic uncertainties in target Vs profile and κ0. The single-station sigma model is developed based on Rodriguez-Marek et al. (Bull Seismol Soc Am 104:1601–1619, 2013) due to the lack of local data. The results of the site-specific partially nonergodic PSHA are discussed by means of a sensitivity analysis and are compared to the results from standard ergodic PSHA. We found that, for the considered site, the site-specific approach provides a substantial reduction (up to 50%) of the uniform hazard spectra at 10,000-year return period compared to the ergodic approach.

Application of Electrical Resistivity Data Sets for the Evaluation of the Pollution Concentration Level within Landfill Subsoil

The paper presents complex analyses of geophysical site investigation results. The electrical resistivity method was used to investigate the potential pollutant migration pathways within areas of existing and former landfill sites. For the purpose of the present study, there were four municipal waste landfills and one industrial landfill chosen for further comprehensive analyses. The landfill bottom was isolated using geomembrane liner. However, ground water monitoring results revealed that the base was not leakage-free. Another two landfills were established in the past, when no containment systems were legally required. The geoelectrical investigation was the final part of an overall analytical assessment of the contaminated sites. The study was aimed at pollution spatial migration analyses and the interpretation of results, for further design of the reclamation and restoration plans. A clear correlation between pollution indicators such as salt compounds and electrical resistivity, allow aerial analyses and the precise determination of contaminated zones. The research results presented in the paper have been recently obtained and concern a period from 2010 to 2015.

Post-Event Site Investigation, Monitoring, Stability Analysis, and Modeling of a Gas Pipeline Explosion

This paper describes the results of site investigations, monitoring, stability analyses, and soil-pipe interaction modeling of a built-up slope located near Pineto (Abruzzo Province, Central Italy), where a gas pipeline exploded on March 6th, 2015, due to heavy rains inducing slope movements. The slope is formed by OC clay, covered with an upper 10- to 14-m-thick clayey-sandy silt colluvial layer. The explosion in the upper portion of the slope caused extensive damage to existing buildings and threatened human lives. Soon after the event, a site investigation and monitoring program was carried out. A detailed topographic survey and hydrological data were analyzed in order to characterize possible critical rainfall events. The stability of the slope was analyzed both in pre- and in post-explosion conditions. The profiles of the DMT horizontal stress index KD helped to identify multiple slip surfaces. Then, the results of the site investigation and stability analyses were used to implement a simplified finite element model aimed to describe the soil-pipeline interaction, taking into account the role of the observed wrinkle in the pipeline. The numerical simulations reveal the crucial role played by the slope movements, and by the wrinkle as well, in inducing the collapse of the pipe.

Seismic response analysis in the southern part of the historic centre of the City of L’Aquila (Italy)

This paper deals in the 2011 extensive site investigation by means of boreholes up to a depth of 80m, Down-Hole (D-H) tests, Seismic Dilatometer Marchetti Tests (SDMT), Multichannel Analysis of Surface Waves (MASW) tests in the area of via XX Settembre of the city centre of L’Aquila (Italy), to obtain a detailed geotechnical model. Results of site investigations showed a marked variability of shear wave velocity Vs profiles, especially in the upper 5–10m, where different soil types are commonly encountered, all characterised by low values of Vs.In this paper the main features of the April 6, 2009 L’Aquila Earthquake (ML=5.8; MW=6.3) are also discussed. The earthquake caused 308 casualties and heavy damage in the city of L’Aquila and in the surroundings villages. Some accelerometric stations were located across the Aterno River Valley, while only one station (namely AQK) was located in the city centre of L’Aquila. The peak acceleration values ranged from 0.35g recorded in the city centre to 0.65g recorded in the middle Aterno valley. The recorded time histories were characterised by short durations and high peak accelerations both in the horizontal and in the vertical directions.The area of via XX Settembre (southern part of the historic centre of the city of L’Aquila) was severely damaged by the earthquake. This area, located at a very short distance from the city centre, includes also some reinforced concrete frame buildings, mostly 5–7 storey high, built between 1950 and 1965. Old masonry buildings and some of these r.c. buildings collapsed or suffered severe damage due to the main shock, causing several tens of victims. The peculiar subsoil conditions locally detected down to about 40m depths in this area include fine-grained soils interposed within, or placed above, “Brecce dell’Aquila” (typical of L’Aquila) and man-made fills. Low and variable shear wave velocity VS values in the upper portion of the subsoil have locally originated major amplification of the ground motion during the main shock.Therefore the paper deals also in specific one-dimensional numerical seismic response analyses performed. Significant amplification effects related to local subsoil conditions, bigger than the amplification factors given by the Italian Building Code NTC 2008, have been discovered by the seismic response analyses carried out at the site. The results of soil response analyses were compared with the occurred damage in the area.

Earthquake-induced deep-seated landslide and landscape evolution process at Hungtsaiping, Nantou County, Taiwan

The Chi-chi earthquake (magnitude 7.6) on September 21, 1999 triggered numerous landslides in central Taiwan. A particularly large, deep-seated landslide occurred at Hungtsaiping, 15 km north of the epicenter. Field investigation and landscape evolution analysis revealed an irregular pattern of displacement vectors, indicating that this failure mechanism is highly complex. This paper presents the results of site investigations in conjunction with simulations of landscape evolution associated with this landslide. Analysis of landscape evolution was based on topographic maps produced at seven different times as well as aerial photographs taken between 1966 and 2006. Landslide site investigation included field reconnaissance, geomorphologic analysis, geophysical exploration, borehole logs, and laboratory experiments. Comprehensive geologic investigation led us to conclude that the materials involved in the landslide are colluvial deposits. Landscape evolution involved at least three large landslide events, two previous rockslides (the first triggered during the 1916 Nantou earthquake and another event occurring in 1934) as well as the 1999 colluvium slide (triggered during the Chi-chi earthquake). By taking into account the source of the collapsed mass, we were able to reproduce the three landslide events using a 3D discrete element model. Calibration of the parameters used in the numerical model was based on the strength characteristics of the rock mass as well as the morphology of the landslide deposits.

“Structural Post-Disaster Damage Classification with Consideration of Liquefaction Due To Flood: Manek Urai, Kelantan, Malaysia”

Natural disasters such as flood which are related to weather, occurring in a lot of places in the world. Environment deterioration and human life damage are the recorded results of floods. Between years 2006 till 2008 due to heavy monsoon rainfalls, a number of floods have generated along Malaysia's in different parts of the country. The critical zones in term of flood damage are located in the east coast of peninsular Malaysia in the states of Kelantan, Terengganu and Pahang. Manek Urai, as a rural area due to its type of buildings was one of the most vulnerable areas during Kelantan flood in 2014. As a proven fact, the victims need to be informed about housing options at the first one week after disaster. The evaluation of building damage must be conducted quickly and exactly. It is a clear fact that building damage survey using proper damage chart is more effective. This paper presents the results of site investigation according to the damage chart for damage assessment, and classifies photographic data of Manek Urai area, based on the damage chart. In addition, the damage chart of timber structures affected by liquefaction is localized.