Detailed Site Investigation Research Articles

Genetic Mechanism and Failure Process of the Mogangling Seismic Landslide

Abstract: This paper presents a case study on the Mogangling landslide and its characteristics and geological mechanism. The Mogangling landslide is a giant rock landslide located at the intersection of Dadu river and Moxi river. It is a landslide triggered by an earthquake with large magnitude that occurred in 18th century. Based on detailed site investigation, it shows the Mogangling landslide developed in the Kangding complex strata, composed of completely decomposed aggregates of massive-block stone, debris and soil with some gravels, pebbles and sand layer found distributed in front of the landslide. The control factor of the deformation of this landslide is the combined effect of Detuo fault which is located under the slope, and the regional stress formed along structural planes as well as the free surfaces formed by river cutting. Therefore, when the Kangding-Moxi earthquake (Ms =7.7) occurred on 1st June, 1786, due to seismic shaking, topographic amplification effects and back slope effects, the Mogangling landslide occurred. The Dadu River is the most important river for hydropower development in China; large-scale seismic landslides along the Dadu River are the most important geological issue during the construction of hydropower stations. Therefore, this research is important from the point of view of economic and social benefits.

Seismic Analysis of the Zipingpu Concrete-Faced Rockfill Dam Response to the 2008 Wenchuan, China, Earthquake

AbstractThis paper presents the findings from both the detailed site investigations and the computational analyses on the Zipingpu concrete-faced rockfill dam (CFRD), a 156-m high dam in which 100-cm permanent settlement and 60-cm horizontal displacement occurred during the 2008 Wenchuan, China, earthquake. The Zipingpu CFRD was 17 km away from the epicenter and was considerably damaged by the Wenchuan earthquake. It was estimated that the peak acceleration in the top of the dam along the axial and vertical direction was about 20.0 m/s2, and the peak acceleration at the river level was about 16.0 m/s2. It was calculated that peak acceleration of dam bedrock was more than 5.0 m/s2, and the intensity (Chinese scale) was more than IX. Based on an in-situ investigation, the peak value of settlement of the dam crest reached 744.3 mm, and the peak value of horizontal displacement toward the right and left abutment are 226.1 mm and 106.8 mm, respectively. The actual experience of the peak acceleration and sei...

Site Investigation of a Loess Slope for a Field Irrigation Test

The Heifangtai plateau, having an area of about 14 km2, has experienced more than 70 loess landslides since 1960s. Aiming at investigating the slope instability induced by irrigation, a field test was proposed. As an important part of the field test, a detailed site investigation was conducted systematically. The topographical details of a typical loess slope at Heifangtai were obtained by a 3D laser scanner. The cracks and the plan view of the site were obtained using GPS. The lithological profile, groundwater level, sampling and soil permeability, were also investigated respectively. On the basis of the site investigation, the field test was conducted successfully.

Stability Calculation of High Side Slope of Diversion Power System Inlet on Left Bank of Jinchuan Power Station

The diversion power system intake excavation of Jinchuan Hydropower Station forms a slope of about 160m height; its stability is one of the main geological problems of the project. By detailed site investigation, the engineering geological characteristics of intake slope (including the lithology, slope structure, the structural surface and its combinations, rock weathering and unloading, hydrology etc) is analyzed in this paper. On the basis of site slope ratio statistics, the problem of how to select a safe and economic excavation slope ratio has been studied. The finite element method and rigid limit equilibrium method were used to calculate and analyze slope stability under various working conditions. The results of analysis evaluation provide a scientific basis for the design and construction.

Sedimentary Characteristics of the Pleistocene Outwash Accumulation and their Implications for Paleoclimate Change in the Midstream of Dadu River, Southwestern China

Abstract:Ancient outwash accumulations, deposited in Pleistocene with complicated sedimentary characteristics, are discovered in the midstream valley of Dadu River, Southwestern China. Their sedimentation characteristics are investigated for gaining a deep insight into the dependency of Paleoclimate changes in this area. This is achieved by means of detailed site investigation, sampling and laboratory tests (grain size distribution and Electron Spin Resonance dating tests) for two representative outwash accumulations. Based on the present study, several main conclusions are drown out as follows: 1) The accumulations are composed mainly of coarse soils (coarse fraction is over 50%) and very coarse soils (coarse fraction is about 20%–35%, and very coarse fraction is over 55%); 2) The coarse soils are sub‐rounded well‐sorted and sub‐stratified to well‐stratified, while the very coarse soils exhibit sub‐rounded to sub‐angular and poorly‐sorted; 3) The accumulations are postulated to have been intermittently deposited in three time periods. This is evidenced by two layers of weathered/residual clay, purple to brick red in color; and 4) It is inferred that the temperature in the study area increased over three time periods, i.e., 280 ka B.P. to 120 ka B.P., 110 ka B.P. to 80 ka B.P. and 70 ka B.P. to 25 ka B.P., and declined twice at 120 ka B.P. and 77 ka B.P. respectively.

A GIS-based methodology for selecting stormwater disconnection opportunities

The purpose of this paper is to introduce a geographic information system (GIS)-based decision support tool that assists the user to select not only areas where (retrofit) sustainable drainage systems (SuDS) could be implemented within a large catchment (>100 ha), but also to allow discrimination between suitable SuDS techniques based on their likely feasibility and effectiveness. The tool is applied to a case study catchment within London, UK, with the aim of increasing receiving water quality by reducing combined sewer overflow (CSO) spill frequency and volume. The key benefit of the tool presented is to allow rapid assessment of the retrofit SuDS potential of large catchments. It is not intended to replace detailed site investigations, but may help to direct attention to sites that have the greatest potential for retrofit SuDS implementation. Preliminary InfoWorks CS modelling of 'global disconnections' within the case study catchment, e.g. the removal of 50% of the total impervious area, showed that CSO spill volume could be reduced by 55 to 78% during a typical year. Using the disconnection hierarchy developed by the authors, the feasibility of retrofit SuDS deployment within the case study catchment is assessed, and the implications discussed.

Lessons learned from three failures on a high steep geogrid-reinforced slope

An excavated slope that connects the school campus and Tai-21 Road is located on the approaching road to Chi-Nan University in Nantou, Taiwan. The toe portion of this high and steep slope is reinforced by a PET geogrid, with the height of the reinforced zone ranging between 10 meters (m) and 40 m at different sections. A slope failure occurred during construction of the reinforced slope in 1994. A massive failure of the reinforced slope then happened at the 40 m high section when the Chi-Chi (Taiwan) earthquake struck on September 21, 1999. The failure portion was rehabilitated, but another failure of the reinforced slope took place at another 20 m high section after a heavy rainstorm on July 2, 2004. The research herein presents the information and the history of these PET geogrid-reinforced slope failures. We perform extensive field observations and numerical analyses to examine the failure mechanism and causes contributing to these failures. Lessons learned from these case histories, with regard to carrying out a detailed site investigation, selecting permeable materials as backfill, installing drainage systems appropriately and combining the design of a reinforced slope with other types of retaining structures to improve the system global stability, are also discussed.

Investigation of the geochemical impact of CO2 on shallow groundwater: design and implementation of a CO2 injection test in Northeast Germany

A small scale and temporally limited CO2 injection test was performed in a shallow aquifer to investigate the geochemical impact of CO2 upon such aquifers and to apply and verify different monitoring methods. Detailed site investigation coupled with multiphase simulations were necessary to design the injection experiment and to set up the monitoring network, before CO2 was injected over a ten-day period at three injection wells, at a depth of 18 m below surface level into a quaternary sand aquifer located close to the town of Wittstock in Northeast Germany. Monitoring methods comprised groundwater sampling and standard analyses, as well as trace element analyses and isotope analyses; geoelectrical borehole monitoring; passive samplers to analyse temporally integrated for cations and multi-parameter probes that can measure continuously for dissolved CO2, pH and electrical conductivity. Due to CO2 injection, total inorganic carbon concentrations increased and pH decreased down to a level of 5.1. Associated reactions comprised the release of major cations and trace elements. Geoelectrical monitoring, as well as isotope analyses and multi-parameter probes proved to be suitable methods for monitoring injected CO2 and/or the alteration of groundwater.

A Preliminary Study on the Transport Behavior for a Potential Disposal Site of LILW in Southern China

Near surface disposal of low and intermediate level radioactive waste (LILW) requires a detailed site investigation of the potential sites, in which the transport behavior of solutes in the groundwater system is one of the key processes that needed to be addressed. An investigation is undertaking for the disposal of LILW at a potential site in Southern China. In-situ test have been conducted to study the hydrogeologic characteristics of the site. Firstly, tests including pit permeability tests, injecting tests, water pressure tests, pumping tests and laboratory permeability tests have been performed according to the specific field conditions. Hydraulic conductivities for different layers of rock and soils have been calculated and their recommended values have been presented. And then in-situ dispersion tests have been performed at an area adjacent to the disposal site with non-sorbed tracers. A numerical model has been developed for the site based on data obtained during the site investigation, and has been calibrated with available measured groundwater level and measured tracer concentrations in the dispersion tests. Calibrated results indicate that the longitudinal dispersion coefficient is equal to 5.0×10-3 m2/d. Preliminary predictions have been performed for the groundwater flow and solute advection-dispersion behavior according to the design of the site, in which the center valley will be backfilled with low permeable materials. Predicted results indicate that the groundwater exhibits a lower water table and a smaller hydraulic gradient under designed site condition than under natural condition. All the tracers remain underground in the site and transport slowly mainly through advection and dispersion. Finally, conclusions for the study have been presented and the key tasks for future work have been discussed. This study provides an insight understanding of the hydrogeology characteristics of the disposal site and is useful for the assessment of environment impacts of the site under disposal of LILW.

‘PRE-CON’ IN WAR DAMAGE RECONSTRUCTION OF TOKYO STATION

Our detailed site investigation on the war damage reconstruction of the Tokyo Station, it was revealed that a lot of “Pre-Con” components were used. “Pre-Con” is the precasted concrete truss construction system developed during and after the war. In this paper, the range and the method of “Pre-Con”’s use in the war damage reconstruction are made clear. In addition, it was assumed that it was clear about introduction process and engineer who concerned with introduction.

Decision Tree Model to Prioritize Signalized Intersections near Highway–Railroad Crossings for Railroad Interconnect

The Manual on Uniform Traffic Control Devices provides a list of factors to be considered when an agency is determining whether a highway–railroad crossing located farther than 200 ft from a signalized intersection should have a railroad-preempted interconnection or be provided with alternative queue management methods. One such factor is the estimated queue length between the signalized intersection and the railroad crossing. Currently, no systematic assessment procedure both (a) quantitatively prioritizes intersections near railroad crossings on the basis of their potential to queue vehicles over the tracks and (b) is reasonably quick to apply agencywide. This paper proposes a decision tree procedure for screening and prioritizing traffic signals near highway–railroad crossings on the basis of estimated queue lengths. An integral component of this procedure is the concept of queue margin, calculated as the difference between (a) clear storage distance between the track and the stop bar and (b) the estimated length of queue traffic. This prioritization procedure was applied to 595 traffic signals in northwest Indiana to prioritize and rank the top 20 intersections for more detailed site investigation. Example intersections are used to illustrate higher-fidelity data collection and queue management strategies.

Risk-conscious Reconstruction in Pakistan-administered Kashmir

The Chakhama Valley, a remote area in Pakistan-administered Kashmir, was badly damaged by the 7.6-magnitude earthquake that struck India and Pakistan on 8 October 2005. More than 5% of the population lost their lives, and about 90% of the existing housing was irreparably damaged or completely destroyed. In early 2006, the Aga Khan Development Network (AKDN) initiated a multisector, community-driven reconstruction program in the Chakhama Valley on the premise that the scale of the disaster required a response that would address all aspects of people's lives. One important aspect covered the promotion of disaster risk management for sustainable recovery in a safe environment. Accordingly, prevailing hazards (rockfalls, landslides, and debris flow, in addition to earthquake hazards) and existing risks were thoroughly assessed, and the information was incorporated into the main planning processes. Hazard maps, detailed site investigations, and proposals for precautionary measures assisted engineers in supporting the reconstruction of private homes in safe locations to render investments disaster resilient. The information was also used for community-based land use decisions and disaster mitigation and preparedness. The work revealed three main problems: (1) thorough assessment of hazards and incorporation of this assessment into planning processes is time consuming and often little understood by the population directly affected, but it pays off in the long run; (2) relocating people out of dangerous places is a highly sensitive issue that requires the support of clear and forceful government policies; and (3) the involvement of local communities is essential for the success of mitigation and preparedness.

기반암 전단파속도의 부지응답특성 영향평가

본 논문에서는 부지응답 해석 시 통제운동 지점의 전단파속도가 부지응답해석에 미치는 영향을 살펴보았다. 내진설계기준 연구(II)(건설교통부, 1997)에서는 '재현주기별 지진가속도의 작용 위치는 "기본적인 지진재해도는 보통암지반을 기준으로 평가한다."라고 정의하고 있다. 그러나 보통암지반(SB)의 전단파속도 범위가 <TEX>$760m/sec{\sim}1500m/sec$</TEX>로 폭넓게 분포되어 있어, 부지응답 해석 시 통제운동지점의 선택에 따라 해석의 결과에 차이가 발생할 수 있다. 따라서, 본 논문에서는 국내의 대표적인 해성퇴적지반층인 인천 및 부산지역의 상세부지조사결과를 바탕으로 1차원 등가선형해석을 수행하였다. 통제운동지점인 기반암 전단파속도에 따른 지층내 가속도의 크기 변화, 그리고 이에 따른 액상화 안전율 변화정도를 살펴보았다. 또한, 해석결과와 외국의 내진설계기준을 바탕으로 국내 내진설계기준의 개선방향에 대하여 살펴보았다. In order to evaluate the effect of shear wave velocity of a seismic control point on site response analysis, one-dimensional equivalent linear site response analysis were performed on the model soil profile based on the results of a detailed site investigation of sedimentary layers at Incheon and Busan. The results of the analysis show that an increase of shear wave velocity on the seismic control point (base rock) results in an increase of acceleration in the soil layers. This was mainly due to an unclear definition of the seismic control point. For this reason, the Korean Seismic Design Standard requires a specific definition of the seismic control point, including spatial conditions and soil properties, similar to the MCE (Maximum Considered Earthquake) in FEMA 369.

Ultra-high-resolution marine 2D–3D seismic investigation of the Liman Tepe/Karantina Island archaeological site (Urla/Turkey)

2D and 3D high-resolution seismic investigations were performed on submerged coastal archaeological sites at Iskele and near to Karantina Island in the Bay of Izmir in western Turkey. Tectonic subsidence of the coastline has submerged a number of archaeological features associated with an important Early Bronze Archaic settlement (Liman Tepe) and the classical Ionian city of Clazomenae. Seismic surveys were focused on imaging of an Archaic harbour structure and other submerged Hellenistic and Roman architectural features. Seismic data were acquired with the SEAMAP-3D ultra-high-resolution 3D marine seismic acquisition system developed for detailed archaeological site investigation. A 2D reconnaissance survey was performed over a 2 km 2 area around Karantina Island to evaluate the seismic penetrability and to locate sites for further 3D investigation. This survey predominantly revealed marine sediment layers covering the local bedrock, which is characterized by scattering of seismic energy showing its rocky nature. Two ultra-high-resolution 3D seismic surveys were performed. The first covered a 350 m × 30 m area in the modern harbour targeting a prominent Archaic harbour structure. The second was acquired across a 120 m × 40 m area on the southeast shore of the Karantina Island close to a Roman architectural feature. The 3D surveys were acquired with nominal line spacings of 1 m, using a 8 × 4 pseudo-rigid hydrophone array and a Boomer source firing at 3 Hz shot frequency. Automated processing of the seismic data using a portable Linux cluster provided stacked 3D seismic volumes with 25 cm × 25 cm bin size on-site. The 3D seismic survey of the harbour clearly imaged the submerged Archaic structure and the underlying sediment sequence. The seismic time slices reveal two seismic anomalies (2–3 m in diameter) in the harbour basin sediments. The 3D surveys southeast of Karantina identified a thicker marine sediment sequence overlying steeply dipping bedrock reflectors. The sediment sequence records the rapid accumulation and progradation of the coastline following the construction the Alexander causeway linking the mainland with the island in 334 B.C.

Environmental problems associated with the development and operation of a lined and unlined landfill site: a case study demonstrating two landfill sites in Patra, Greece

The present work demonstrates the environmental problems associated with the development and operation of a lined and unlined landfill site, both used for municipal solid waste landfilling, that are situated next to the city of Patra, Greece. Findings from a detailed site investigation as well calculations on hydrologic evaluation of landfill’s performance and measurements on leachate composition proved that the lined landfill site is more secure and environmental friendly compared with the unlined landfill site. Even though, until today, there is no evidence from near boreholes for severe contamination problems generated by any of the two landfills, in the forthcoming future several environmental problems are expected to occur from the unlined site. In addition the prevailing hydrogeotechnical conditions indicated that the unlined site is a potential source of contamination; hence extra remedial measures should be received by the local authorities to prevent severe contamination in soil and groundwater.

Geotechnical properties of Dublin Boulder Clay

Geotechnical characteristics of Dublin Boulder Clay (DBC), based on detailed site investigation and site experience from some recent large projects in Dublin, are presented. This paper attempts to synthesise available information in parallel with recent work by Skipper et al., who provide an updated understanding of the geology of the DBC. Having assessed the effects of sampling disturbance, the paper characterises the various formations and sub-units of the DBC. The interpreted material behaviour is related to observed engineering performance. It was found from the behaviour of earth retained structures that intact, clayey, DBC formations are two to three times stiffer than assessed from high-quality laboratory tests on block samples. DBC is shown to be significantly stiffer than other well-characterised tills. Relatively inexpensive multichannel surface wave techniques can give very reliable estimates of in situ small-strain stiffness. High undrained triaxial compression strengths were measured, and it appears that simple UU tests on high-quality specimens give good results. Significant strength anisotropy was suggested by undrained triaxial extension strengths that were only 30–50% of the triaxial compression strengths. Field horizontal permeability values of the intact clayey till units have a representative mean of about 10−9 m/s, and when compared with laboratory values suggest that the material may exhibit some degree of anisotropy of permeability. Overall, the measured engineering parameters for the DBC are favourable for many construction projects. Further work is required in order to understand the in situ horizontal stress profile and the stiffness anisotropy of the till.

Rehabilitation of field tunnel erosion using techniques developed for construction with dispersive soils

Past repairs of field tunnel erosion using mechanical treatments (deep ripping, contour furrowing, contour ripping, etc.) and reestablishment of perennial vegetation have often failed, resulting in further tunnelling. Techniques to prevent ‘piping’ (tunnel erosion) in earth dams constructed using sodic clays have not been used in the repair of field tunnel erosion; however, these techniques have the potential to reduce recurrent failure. Installation of an optical fibre cable in a Grey Sodosol and Grey Dermosol at a site near Dunalley, Tasmania, in November 2001, resulted in the formation of a 380-m-long tunnel erosion system. Detailed site investigations and soil analysis in 2004 indicated that the tunnel erosion resulted from the consequences of inadequate compaction during the installation of the optical fibre cable, and secondary processes such as capture of surface and subsurface flow, dispersion of sodic clays, and translocation of dispersed clay platelets through the poorly compacted fill. Repair works consisted of excavating the entire length of the tunnel system, chemical amelioration with gypsum, compaction of repacked fill to reduce internal porosity, and installation of sand blocks to capture and remove water moving along the reinstalled cable. Inspections conducted 2 years after completion of the repair works indicated the site to be stable; however, it is acknowledged that this is too short an interval to adequately assess the long-term stability of repair works and techniques employed at the site. Due to the costs associated with the application of dam construction techniques, their use for the repair of field tunnel erosion is likely to only be justified where continued erosion poses a risk of damage to high value infrastructure.

A geohazard reconnaissance study based on geoscientific information for development needs of the western region of Istanbul (Turkey)

The role of geoenvironmental information is becoming increasingly important as legislative changes have forced developers and planning authorities to consider more implications and impact on the environment of large-scale development initiatives. Therefore, integration of surface and subsurface geoscientific information for development needs has prime importance and provides a means of identifying potential problems and opportunities at an early stage in any planned development. However, from the experience of recent natural disasters, it is evident that this was not case the taken into consideration in many countries. In addition to thousands of casualties, many urbanized areas, industrial districts and large-scale engineering structures suffered severe damages from the natural hazards due to many reasons including the lack of preliminary engineering geological maps and zoning maps of the settlement areas. Turkey is one of the countries which is exposed to natural hazards such as earthquakes, landslides and floods. In particular, the devastating 1999 Kocaeli earthquake, which affected the Marmara Region of Turkey, focused the attention on densely urbanized and industrialized metropolitan areas such as Istanbul. The rapid growth of Istanbul, particularly towards west with minimal geoscientific information resulted in an overwhelming pressure on the natural environment. In addition, a large earthquake, which is expected to occur in the Marmara Sea within the next 30 years, also pose a threat to the city and its surroundings. In this study, on the basis of the geological, geomorphological and geophysical reconnaissance study, an integrated geoscientific data were collected from the western region of Istanbul and evaluated for geohazards. The paper focuses on the geological and geomorphological aspects that control the occurrence of some geohazards such as earthquake-induced liquefaction, landslides and flooding. In this context, the geological map of the region was revised and Quaternary deposits were classified into 11 units, in detail. Liquefaction-prone areas were evaluated by using geomorphological criteria based on field investigation, by the examination of the available records from 88 boreholes drilled on recent deposits and by the data from resistivity profiles. The landslides within the region were classified according to their type, relative depth and activity. In addition, fluvial and marine flood-prone areas were also delimited within the region. Finally, a series of maps such as landslide inventory maps, and maps showing liquefaction- and flood-prone areas were produced with the aid of Geographic Information Systems (GIS) to assist in designing further detailed site investigations and to reduce costs by ensuring a more focused approach to strategic planning and site selection.

A size classification for debris flows

A 10-fold classification for debris flow size is proposed based on total volume, peak discharge and area inundated by debris. Size classes can be used for regional overview studies where detailed site investigations are either unnecessary, too costly or where the highest hazard and risk creeks need to be identified for further study. They are also useful to compare the regional impact between affected areas and the effects of rainstorms, and they allow lay-people to obtain an understanding of debris flow magnitude and consequences. Finally, different size classes allow the estimation of travel times to points of interest based on empirically derived equations. It is proposed that agencies concerned with debris flows should establish a documentation of debris flow size according to this classification, which serves as a data base for hazard and risk planning.

Part 6: Tunnels and Underground Structures: Pressuremeter Investigation for Mass Rapid Transit in Bangkok, Thailand

The 20-km (12.5-mi) mass rapid transit underground railway system in central Bangkok, Thailand, recently opened for passengers. During construction, the project was divided into two separate civil design–build contracts: the northern section, comprising approximately 10 km (6.2 mi) of twin bored tunnels, and nine stations constructed within slurry walls by adopting top-down techniques. A crucial part of the design of the underground structures was the selection of appropriate design parameters for the slurry walls. The contractor was responsible for ground-related issues and carried out a detailed site investigation to confirm the ground conditions and define soil parameters for the design of the underground structures. The site investigation comprised 40 conventional wash-bored borings and six self-boring pressuremeter tests. This paper describes the site investigation that was carried out for the project and the ground conditions that were encountered, with particular focus on the use of the self-boring pressuremeter to estimate the soil strength, stiffness, and in situ pressure for use in design of the slurry walls. The paper discusses the various methods used to interpret the data and compares the parameters derived from the pressuremeter to those derived from other methods and from back-analysis of the behavior of the wall during construction. It is concluded that in the conditions in Bangkok, the pressuremeter testing provided higher strength and stiffness values than determined from other methods and that these parameters were subsequently borne out by the behavior of the underground structures.