Geotechnical Information Research Articles

Linking Site Investigation Efforts to Final Design Savings with Simplified Reliability-Based Design Methods

AbstractThis study aims to address how efforts spent in geotechnical site investigation can be linked in an objective and defensible way to the final design dimensions of a geotechnical structure. A previously developed pad foundation example is adopted for illustration. Three aspects of geotechnical information are addressed: a variety of in situ and laboratory tests, precision of the tests, and local experiences in the estimation of soil properties that permit reduction of transformation uncertainties between test indexes and design parameters. Four simplified reliability-based design methods based on partial factors and quantiles are calibrated for the pad foundation. Their performances in linking site investigation efforts to final design savings are studied. Among these methods, the quantile methods are found to be the most responsive to the availability of geotechnical information, whether in the form of site investigation efforts or local experiences. The quantile methods can fill a critical gap in...

Comparative study of different inversion techniques applied on Rayleigh surface wave dispersion curves

ABSTRACTThis study examines the performance of different inversion techniques applied on Rayleigh surface wave dispersion curves. The kriSIS algorithms implement the Quasi‐Newton method, the L1 norm minimization, smoothness, damping and minimum gradient constraints and their combinations, as well as weighted inversion. Furthermore, any a priori geophysical or/and geotechnical information can be taken into account during the inversion. The proposed methodology is applied on two synthetic dispersion curves as well as two synthetic seismic records. Eight inversion parameters were tested per examined model resulting in 7680 tests. Three of them were tested on real data. The main outcome of this comparative study indicates that, for the tested models and real data, the Least Squares (L2 norm) inversion, using smoothness constraint and calculating the Jacobian matrix from analytical relationships or arithmetic differentiation, leads to the most reliable and accurate inversion results.

Evaluating the effectiveness of rolling impact compaction at a brownfield site with high and low frequency seismic surface waves and geotechnical testing

ABSTRACTUsing a case study from a brownfield site in Australia that contained substantial uncontrolled crushed rock fill, we demonstrate that innovative geophysics and ground improvement using rolling dynamic compaction can provide alternatives to costly excavation, removal and re‐engineering of soils. This approach can also overcome some of the limitations of conventional geotechnical testing in such conditions. The process we have developed involves selection and levelling of trial areas within larger brownfield sites. These are initially screened with electromagnetic geophysics to target environmental sampling sites, buried objects and local areas of potentially unsuitable or contaminated soils for removal and replacement. High and low frequency surface wave testing is then completed along closely spaced lines within the trial areas using specially adapted Multi‐channel Analysis of Surface Waves (MASW) methods and a modified land streamer. This provides S‐wave velocity distributions within fill and deeper materials over two depth ranges, at high vertical resolution from approximately 0 to 2 m and at lower resolution from 2 to ~10 m. These results are compared with geotechnical engineering test information. Ground improvement works are then undertaken using rolling dynamic compaction with a ‘square’ impact roller.Within this brownfield trial area, geotechnical testing showed that post‐compaction in‐situ densities increased by about 6 to 10%, while S‐wave velocities increased by up to 40%. This clearly demonstrates the sensitivity of S‐wave velocities to soil and fill modulus. The S‐wave velocity sections also showed the consistency of the landform created by impact rolling and that both high and low frequency MASW testing is needed for more accurate assessment of the densification of both shallow and deeper fill. Normalized S‐wave velocity difference sections and Cone Penetrometer Testing (CPT) provided a clear indication of the depth of influence of the impact rolling.A relationship was developed between post‐compaction S‐wave velocity and Dry Density Ratio (DDR) that formed the basis of a viable geotechnical verification strategy for the ground improvement works on the larger brownfield site. Electromagnetic and advanced surface wave geophysics, combined with innovative ground improvement methods by rolling dynamic compaction, represent an advance over current practice for brownfield site development.

토양의 함수율에 따른 전기비저항 반응 모형 실험 연구

지반조사에서 비파괴 조사 기술은 시추조사보다 경제적으로 비용이 덜 들고 광역에 걸친 지반정보를 제공하는 장점이 있다. 하지만 지반설계정수로서 적용하기에는 어려운 한정된 정보만을 제공하게 된다. 이를 극복하기 위해, 비파괴 조사 방법 중 하나인 전기비저항 탐사를 모형토조실험에 적용하여, 토질상태에 따른 비저항 반응과 함수비에 따른 비저항 반응을 분석하여 비저항 거동 양상에 대한 연구를 수행하였다. 실험에 사용한 토질은 주문진 표준사, 마사토이며 각 토질의 입도 분포, 균등계수를 구하여 실험에 있어 실험재료의 균질한 상태를 유지하였다. 실험에 사용한 모형의 제원은 <TEX>$160{\times}100{\times}50$</TEX> (cm)의 아크릴 재질 토조이며, 각 토질의 높이는 30 cm를 유지하였다. 5TE(함수비측정센서)센서를 7 ~ 8cm 간격으로 수직하게 꽂아 층별 함수비를 측정하였다. 모형실험 결과 주문진 표준사는 비저항 거동 양상이 함수비에 민감하게 반응하는 것을 알 수 있었으며, 마사토는 함수비에 따라 비저항이 낮아진 후에도 시간경과에 따른 거동 양상에 큰 변화가 없는 것을 관찰하였다. 또한 토조 실험에 사용된 토양과 유사한 테스트 베드를 선정하여 그 반응을 비교 분석하였다. 이러한 실험을 통해 토질 상태와 함수비에 따른 다양한 비저항 거동 양상 자료를 수집하고, 비파괴 조사기술의 정확도를 향상 시켜 나간다면 지반설계정수를 산정하는데 있어 기초적인 연구가 될 수 있음을 확인하였다. Geophysical investigation in non-destructive testing is economically less expensive than boring testing and providing geotechnical information over wide-area. But, it provides only limited geotechnical information, which is hardly used to the design. Accordingly, we performed electrical resistivity experiments on large scale of soil model to analyze the correlation between electrical resistivity response and soil water contents. The soils used in the experiments were the Jumunjin standard sand and weathered granite soil. Each soil particle size distribution and coefficient of uniformity of experimental material obtained in the experiments were maintained in a state of the homogeneous. The specifications of the model used in this study is <TEX>$160{\times}100{\times}50$</TEX>(cm) of acrylic, and each soil was maintained at the height 30 cm. The water content were measured using the 5TE sensors (water contents sensors) which is installed 7 ~ 8 cm apart vertically by plugging to floor. The results of the resistivity behavior pattern for Jumunjin standard sand was found to be sensitive to the water content, while the weathered granite soil was showing lower resistivity over the time, and there was no significant change in behavior pattern observed. So, it results that the Jumunjin standard sand's particle current conduction was better than the weathered granite soil's particle through contact with the distilled water. This lab test was also compared with the result of a test bed site composed of similar weathered soil. It was confirmed that these experiments were underlying research of non-destructive investigation techniques to improve the accuracy to estimate the geotechnical parameter.

Using Geographic Information Systems (GIS) in Soil Classification and Analysis in Gaza City, Palestine

Geographic Information System (GIS) can integrate and relate any data with a spatial component regardless of the source of data. It's easy to store, retrieve, manage and analyze geotechnical data. In this study Geotechnical field was chosen because Gaza Strip governorates lack studies in this field. Given that there is a large quantity of data in hard copy format which is difficult to handle without the implementation of GIS. Thus Gaza City has been selected as a case study. This research aims to investigate the development of a Geographic Information System (GIS) to better collect, manage, analyze and visualize soils data which obtained from boreholes test results collected from 92 boreholes covering about 70% of Gaza City. The methodology applied is divided into several stages including data compilation and editing, preparing data for analysis, archiving, analyzing and presentation. This research presents the results of soil logs (2D or 3D logs) and their engineering properties for any specific location that may be chosen. Models, sections, profiles and fences can also be obtained. In addition to Maps as bearing capacity, water content, type of foundation, excavation depth and lithology planer map at any depth can be created through employing GIS technology. Finally, the research provides engineers with the necessary geotechnical information for designing construction in the different projects as buildings, towers and roads.

Remediation of karst concerns in the valleys of the Northeastern United States

The valleys within the Appalachian Mountains are often floored by carbonates. When remediating or preventing sinkhole activity in any karst, consideration should be given to a number of geologic, geotechnical and environmental concerns. Primarily, one must recognize that Appalachian karst is most likely variably faulted and folded and cannot be evaluated in the same manner as the flat-lying carbonates of the mid-continental US or the lightly cemented, recent karst of Florida. Also, in the tectonically abused rocks of the northeastern US, with their resultant solutioned discontinuities, one must also recognize the possible effects that glaciation may have had in the more northerly portions of the region. Investigative tools that can aid in deciphering these considerations include aerial imagery, review of sinkhole maps, geologic reconnaissance, test pits, test borings and percussion probes. In the authors’ experience geophysics, unless combined with hard data, rarely provides useful geotechnical information even when costly programs are performed by competent individuals. Depending upon the nature of the sinkhole/doline and its effects upon man-made and natural environments, a number of effective remedial measures are available. This paper briefly addresses these various types of remediation including high and low mobility grouting, drainage maintenance, dynamic compaction (destruction) and structural solutions in relation to the encountered conditions, with consideration for economics, and will present case histories illustrating a number of problems and solutions in discussion.

Seismic microzonation for the northeast Texcoco lake area, Mexico

The Texcoco Lake area is currently undergoing a rapid urbanization. This has required designing and building strategic infrastructure. However, this zone has been poorly explored, and thus, a building code design response spectrum is not available. This paper presents the exploration and laboratory works, as well as the analytical studies conducted for obtaining a design response spectrum for the northeast Texcoco Lake area. From geotechnical information gathered previously for other projects in the studied zone, and applying the ordinary kriging technique, the necessary dynamic soil parameters for site response analysis were determined. A total of 2501 virtual soil profiles were generated. The seismic environment was characterized throughout a uniform hazard spectrum obtained in a nearby rock outcrop. Probabilistic site response analyses were performed using the uniform hazard spectrum computed in rock as input motion for all 2501 virtual profiles. Finally, a design response spectrum for the studied area was proposed.

CoalLog: the standard for collection, recording, storage and transfer of geological and geotechnical data for the Australian coal industry

A standard has been developed to improve and upgrade the collection and coding of geotechnical data as part of geological exploration activity. CoalLog was developed by industry-based geoscientists and geotechnical specialists in response to outdated terminologies, non-translatable data coding, and non-conformances with relevant Australian and international standards for geotechnical investigation, testing, and reporting. The new standard will allow the industry to use geotechnical information efficiently and accurately, thereby minimising potential legal liabilities associated with non-conformance to recognised standards that are already in place in the non-coal geotechnical sector. Adoption of this standard will also promote opportunities for a wider range of geotechnical specialists to provide services to the coal industry.

Soil characterization for seismic damage scenarios purposes: application to Angra do Heroísmo (Azores)

Angra do Heroismo, the main town of Terceira Island in the Azores Archipelago, was hit in 1980 by a 7.2 magnitude earthquake that caused great destruction in the central part of the town. Taking into consideration the high seismic hazard of the region and the cultural and social importance of Angra do Heroismo, the elaboration of damage scenarios is of particular importance to implement measures for preserve and protect the town against future earthquakes. The first step is to perform microzonation studies in order to characterize the soil seismic behaviour. Taking into consideration the available geologic, geotechnical and geophysical information, a detailed soil characterization was performed based on the results from numerical modelling and the analysis of microtremor experimental measurements. Nine different soil profiles were identified, characterized and classified. Discussion on the detailed soil classification and the Eurocode 8 soil classification is presented. This study shows that even with an available code, microzonation studies must be developed in order to identify differences on soil behaviour inside the interested area. It shows also that the use of experimental measurements presents a great help on soil characterization. The obtained detailed classification will be used on the estimation of damage scenarios for Angra do Heroismo.

A New Approach to Quality Detecting and Measuring of Earth-Fill Dam

Based on some at present advanced geophysical methods, a non-destructive detection method mainly depending on ground penetrating radar(GPR) has been established by combining with Rayleigh wave method and natural electrical field method. The quality of earth-fill dam not only can be evaluated and analyzed quickly, but also multi-method, multi-parameter, multi-information can be undertaken quantitative analysis through considering geo-technical test and geophysical information. After this method has been successfully applied to Xixia earth-fill dam detection, it is indicated that modern geophysical methods is effective to detect the diseases and faults in dam quality and this method is worthy of popularizing and application in the future.

Fundamental Study on Support Systemat Cibaliung Underground Gold Mine, Indonesia

Geotechnical information is a key for underground design. The most important parameters are rock mass strength, geological structures, main stress and strain, rock mass classification, discontinuities, etc. All of these may have impact on undergrou nd stability, if some are suitable, and only just one is troubled, it can be due to instability in the underground.The purposes of this study are to classify the rock mass and to introduced the support system in Cibaliung underground gold mine based on the rock mass classification. The characteristics of some geotechnical aspects of Cikoneng and Cibitung area are shown in this paper. Rock mass classification is measured, and the difference between both locations presented as a preliminary study for the next further research. Recommendation of support system policy of Cibaliung underground gold mine which compared to Pongkor underground gold mine also discussed in this paper.

Engineering-geological conditions of the formations in the Western Thessaly basin, Greece

AbstractAn engineering-geological map of the Western Thessaly basin has been compiled, providing a valuable guide to both urban planning and industrial development of the wider area. This map contributes significantly to the optimization of land use and improved planning of technical work. Additionally, the engineering-geological conditions of the formations encountered in the Western Thessaly basin are examined. The formations are grouped into thirteen (13) engineering-geological entities, with regard to their geotechnical behaviour. This entire study was based on both in situ investigations and geotechnical information extracted from 1,039 boreholes.Furthermore, a landslide inventory map of the Western Thessaly basin has been compiled. In addition, the surface subsidence ruptures, due to ground-water overexploitation, have been examined in the eastern part of the study area.

Application of Airborne EM to Bowen Basin Coal Projects

In 2011, several Bowen Basin coal exploration projects in central Queensland were surveyed with the SkyTEM airborne electromagnetic system. The aim of these surveys was to trial the effectiveness of the method in for coal applications, with specific focus on mapping the key aspects of the weathering, overburden and hydrology that are most important for effective development of a coal project. The first survey, which was over an area near Moranbah with 150m of Tertiary overburden with extensive basalt flows, mapped crucial hydrological and geological features important to efficient further development of the project: These included a) a convoluted network of basalt-filled palaeochannels, some of which extend through and into the coal measures b) location, extent and thickness of major saline aquifers, c) depth to base of Tertiary. Subsequent surveys over different parts of the Bowen basin, showed that SkyTEM was a very effective tool for mapping the thickness of weathering, a parameter very important for drilling out coal resources. The results are surprising in that they not only provide a detailed map of depth of weathering (including volumes of lateritic sediments requiring excavation), but also map more subtle geological features such as synclines (previously only loosely inferred from surface mapping), major faults, previously unknown dykes, dip and strike of the main stratigraphic units, fresh water aquifers and even possibly also various coal seams (generally because they are saline aquifers). These surveys represent, at least to the authors? knowledge, the first example of modern helicopter-borne transient EM in the Australian coal fields. The results from this project and subsequent projects are surprising in that they have had unexpected applications above and beyond those which were originally forecast. Thus, with informed and thorough use, airborne EM promises to deliver valuable geological and geotechnical information to aid in the further development of Australia?s coal resources.

Japan’s Nation-Wide Electronic Geotechnical Database Systems by Japanese Geotechnical Society

On October 15, 2010, the Japanese Geotechnical Society (JGS) announced the public release of ‘Nation-wide Electronic Geotechnical Database Systems,’ which provides geotechnical information to the public on the internet. The information the system provides is a collection of ground models at 250 m by 250 m in plan built by using data from various geotechnical information databases. The paper first describes historical development of the geotechnical information databases in Japan, and introduces a 5-year project, ‘Integrated Geophysical and Geological Information Database in Japan,’ led by the National Research Institute for Earth Science and Disaster Prevention (NIED), and participated by the JGS. The paper then presents the JGS’ ‘Nation-wide Electronic Geotechnical Database Systems,’ and describes why such system was proposed and built, followed by the presentation of the examples for possible application of the system.

Forensic Diagnosis on Flood-Induced Bridge Failure. I: Determination of the Possible Causes of Failure

In Taiwan, many bridges span rivers that exhibit severe channel variations in response to drastically increased flows and resulting floods caused by typhoons and storms. Flood-induced scour can undermine the effective embedment depth of bridge foundations. The Shuang-Yuan Bridge, spanning a downstream section of the Kaoping Stream, was severely damaged during Typhoon Morakot in August 2009. A qualitative investigation was conducted to determine the possible causes of this bridge collapse. Relevant hydrologic, meteorologic, structural, geotechnical, and terrain information from various sources both in written and image formats was collected, updated, and reviewed. The disaster investigation included field investigations, nondestructive inspection of bridge remnants, and investigation of structural damage of upstream river crossings, hydrologic changes, damage to training structures/embankment, riverbed profile changes, and debris during the flood event. Several inspections were applied to determine the embedment depths, positions of underwater remnants, and changes in riverbed elevation. The investigation results identified multiple possible causes of failure, including flood flows, river-bend-induced turbulent flows, and the joint effects of extended foundations and rafted wood.

Value of Geotechnical Site Investigation in Reliability-Based Design

This study aims to address how efforts spent in geotechnical site investigation can link to the final design dimensions of a geotechnical structure. An example of pad foundation design supported by boulder clay (developed by European Technical Committee 10) is used as a demonstration. Three aspects of geotechnical information are addressed: variety of in-situ and laboratory tests, precision of the tests, and local experiences in soil properties that permit reduction of transformation uncertainties between test indices and design parameters. Three design methods (allowable stress design ASD, partial-factor design PFD, and reliability-based design RBD) are considered. Among these methods, RBD is found to be most responsive to the availability of geotechnical information, whether in the form of site investigation efforts and/or local experiences. It is accurate to say that RBD can fill a critical gap in current geotechnical design practice, namely to monetize the value of geotechnical information in the form of increase/reduction of construction costs associated with changes in the design dimensions.

Geoenvironmental evaluation for planning: an example from Gumushane City, close to the North Anatolia Fault Zone, NE Turkey

The paper highlights the importance of establishing an appropriate database of information to assist planners in site selection and decisions regarding land usage. Such a database should include geological and geotechnical information, but this should be assessed from a geoenvironmental viewpoint. The city of Gumushane in the Black Sea region is discussed, as this area is close to the North Anatolia Fault Zone and there is a shortage of “suitable” ground for development.

Mapeo de ingeniería geológica en parte sur del Área Metropolitana de San Salvador

El uso de mapas geológicos clásicos que agrupan los estratos por edad u origen, dificulta la interpretación y uso para diseños de ingeniería civil o planificación urbana, para las personas sin conocimientos profundos en geología. Debido a esto se ha llevado a cabo mapeo de ingeniería geológica en sector sur del Área Metropolitana de San Salvador, haciendo uso de la metodología de bandas. El objetivo de la metodología es que la información geológica, peligrosidad geológica y recomendaciones geotécnicas puedan representarse y agruparse dependiendo de las características intrínsecas de cada zona. Esta información puede ser fácilmente interpretada por los planificadores urbanos, constructores privados y agencias gubernamentales. La debilidad en la recopilación e investigación de información geológica y geotécnica en El Salvador, son unas de las razones de la problemática que experimenta la región, indicando la importancia de mejorar el manejo del riesgo, así como la mecánica de suelos y de rocas.

Joint application of ground penetrating radar and electrical resistivity measurements for characterization of subsurface stratigraphy in Southwestern Nigeria

The frequent building collapses in Nigeria have been attributed to a lack of pre-construction investigations, which assist engineers in obtaining in situ geotechnical information. Further, the structural subsurface settings are often ignored or investigation is haphazardly carried out. To address this issue and demonstrate the importance of such a survey, a combination of ground penetrating radar (GPR) and vertical electrical sounding (VES) data were acquired in a part of Southwestern Nigeria. A 200 MHz antenna was used for the data acquisition along four traverses. The data were subjected to standard GPR processing techniques, and attribute analysis such as instantaneous frequency, amplitude and phase. Also, for comparative and engineering characterization purposes, longitudinal conductance and coefficient of anisotropy were computed from the VES results and used for determining the competency of the bedrocks. From the GPR results, it was observed that the mapped subsurface is characterized as erosional truncated at a low angle, which is southerly dipping and includes tangential reflections. Further, stratified rocks dipping at an angle of 32° occur between 1.0 and 4.5 m depth in all of the GPR sections; these strata were truncated by topsoil at shallow depths. Also, some of the sections depict ancient channel structures that have a dimension of 70 m × 40 m. The resistivity data suggest that the study area is characterized by four distinct geoelectric sequences. These comprise topsoil which is composed of clay-like sand to lateritic clay whose thickness ranges between 0.25 and 8.12 m, weathered bedrock with a thickness between 3.84 and 12.61 m, stratified bedrock with a thickness between 0.33 and 7.51 m, and fresh bedrock. These results reveal a complex subsurface geology and this characterizes the study area. The area has low to moderate longitudinal conductance and coefficient of anisotropy values, which suggest that incompetent to semi-competent bedrock exists beneath the subsurface. A good correlation between the GPR and resistivity derived thicknesses was established.

Comment on &amp;quot;Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L'Aquila regarding regional geotechnical information&amp;quot; by Prattes et al. (2011)

Abstract. Prattes et al. (2011) report ULF magnetic anomalous signals claiming them to be possibly precursor of the 6 April 2009 MW = 6.3 L'Aquila earthquake. This comment casts doubts on the possibility that the observed magnetic signatures could have a seismogenic origin by showing that these pre-earthquake signals are actually part of normal global geomagnetic activity.