Effective Site Investigation Research Articles

Qualitative evaluation of thaw settlement potential in permafrost regions of Canada

Permafrost thaw negatively impacts the built environment in circumpolar regions. Thaw-induced settlement causes various engineering problems such as differential settlement, sinkholes, culvert failures, and pipeline deformations. Large-scale pre-construction evaluation reduces the risk of building infrastructure in thaw settlement-prone areas. This evaluation enables the comparison and screening of multiple route/location alternatives, the identification of vulnerable sections of a route, and the development of more effective site investigation plans. This study presents a systematic approach for evaluating thaw settlement potential in various regions across Canadian permafrost. In developing the approach, we considered three main factors: ground ice content, surficial deposit unit, and bedrock type. These factors were prioritized based on their relative importance in defining settlement behaviour, and a weighting factor was determined for each. In this study, the weighting factors of 0.78, 0.15, and 0.07 were suggested for ground ice content, surficial deposit type and bedrock type, respectively. We subsequently developed a Thaw Settlement Potential Index (TSPI), which can be calculated for any given location using publicly available Canada-wide resources. We calculated TSPI for several reported cases of thaw settlement issues across Canada and compared the results with site observations. A comparison was also made with a more detailed assessment conducted on the Northern Alaska Highway using a different approach. While the TSPI assessment required minimal time, effort, and resources, the obtained results generally matched those of finer-scale assessments with more detailed information. Thus, our methodology simplifies early identification of thaw-unstable regions in projects with large footprints and helps allocate resources more efficiently for subsequent site investigations.

Breakthrough in 2D‐CSIA Technology for 1,4‐Dioxane

A dual isotope technology based on compound‐specific stable isotope analysis of carbon and hydrogen (2D‐CSIA) was recently developed to help identify sources and monitor in situ degradation of the contaminant 1,4‐dioxane (1,4‐D) in groundwater. Site investigation and optimized remediation have been the focus of thousands of CSIA applications completed for volatile organic contaminants (VOCs) worldwide. CSIA for the water miscible 1,4‐D, however, has been technically challenging. The most commercially available sample preparation settings “Purge and Trap” for VOC could not efficiently extract 1,4‐D out of water for a reliable CSIA measurement, especially when the concentration is below 100 μg/L. Such a high reporting limit has prevented CSIA from being used for effective site investigation and remediation monitoring at most 1,4‐D contaminated sites, where 1,4‐D is often present at very low ppb levels. This article outlines the recent breakthrough in 2D‐CSIA technology for 1,4‐D in water, reported down to ∼1 μg/L for carbon, and ∼10 μg/L to 20 μg/L for hydrogen using solid‐phase extraction based on EPA Method 522, and its benefit is highlighted through a case study at a 1,4‐D contaminated site. ©2016 Wiley Periodicals, Inc.

Anomalous buried hollows in London: development of a hazard susceptibility map

Engineering works carried out in central London over many decades have revealed a number of buried hollows that exhibit curious characteristics. Some extend deep into the bedrock geology and are in-filled with disturbed superficial deposits and reworked bedrock. Others are contained within the superficial deposits. They can be up to 500 m wide and more than 60 m in depth. As the infill material often has different behavioural characteristics from the surrounding deposits failure to identify them during an initial site investigation can prove costly. This paper considers their common characteristics and describes the method used to develop a buried hollow hazard susceptibility map. This map provides planners with a broader awareness of the potential location of difficult ground conditions associated with them, thereby reducing the potential for unforeseen ground conditions through effective site investigation design. The paper continues with a discussion of some of the likely processes associated with their formation, which are attributed to cryogenic processes, and concludes with potential future research directions.

Scale Effects and Field Applications for Continuous Intrusion Miniature Cone Penetrometer

콘관입시험은 현장조사 시험법으로 사용 빈도가 증가되고 있다. 그러나 콘관입시험은 콘크기와 용량 등에 따라 적용 가능한 현장조건이 제한되는 단점이 있다. 소형콘의 감소된 단면적은 시스템 용량을 증대시켜 적용성을 향상시킬 수 있으며, 코일식 롯드를 이용한 연속관입 시스템은 신속하고 경제적인 지반조사를 가능하게 한다. 본 연구에서는 국내 여러 현장에서 연속관입형 소형콘관입시험 시스템의 성능을 표준 콘관입시험 시스템과의 비교시험을 통하여 평가하였다. 소형콘관입시험 장비는 기존의 표준콘관입시험 장비와 비교하여 지반정수 도출 및 지반분류에 동일한 성능을 발휘하는 것을 확인하였으며, 장비의 기동성 및 적용대상 토질 확대 등의 장점을 나타내는 것으로 평가되었다. 크기효과 검증을 위한 현장시험 결과 기존 시험 방법에 비해 콘저항력의 경우는 약 10% 과대평가하는 것으로 나타났다. 차량 형태의 조사장비는 표층이 연약하거나 진입이 어려운 경우에는 조사의 한계가 있으므로, 궤도장치에 탑재된 연속관입형 소형콘관입시험 시스템으로 개선하여 적용성을 확대시켰다. 따라서 개선된 연속관입형 소형콘관입시험 시스템은 연약지반 심도탐지 및 흙분류시 경제적이고 신뢰성 높은 지반조사 방법으로 활용할 수 있다. Cone penetration tests (CPTs) have been increasingly used for site characterizations. However, the site investigations using CPTs are often limited due to soil conditions depending on the cone size and capacity of the CPT system. The small sectional area of a miniature cone improves the applicability of the CPT system due to the increased capacity of the CPT system. A continuous intrusion system using a coiled rod allows fast and cost effective site investigation. In this study, the performance of the continuous intrusion miniature cone penetration test (CIMCPT) system has been evaluated by comparison tests with the standard CPT system at several construction sites in Korea. The results show that the CIMCPT system has a same performance with the CPT system and has advantages on the mobility and applicability. According to field verification tests for scale effect evaluation, the cone tip resistance evaluated by CIMCPT overestimates by 10% comparing to standard CPTs. A crawler mounted with the CIMCPT system has been implemented to improve accessibility to soft ground, and has shown improvement over the truck type CIMCPT system. Therefore, the improved CIMCPT system can be utilized as a cost effective and highly reliable soil investigation methodology to detect the depth of soft ground and to evaluate soil classification.

Discussion: Towards reliable and effective site investigations

R. Baker, M. B. Jaksa, J. S. Goldsworthy, G. A. Fenton, W. S. Kaggwa, D. V. Griffiths, Y L. Kuo and H. G. Poulos

Towards reliable and effective site investigations

It is widely appreciated that, in civil engineering and building projects, the largest element of financial and technical risk usually lies in the ground. Almost exclusively, the scope of geotechnical investigations is governed not by what is needed to characterise the subsurface conditions appropriately but, rather, by how much the client and project manager are willing to spend. There is often little correlation between the variability of the ground and the scope of the investigation. This paper presents the results of a Monte Carlo simulation incorporating many 3D single-layer soil profiles with different statistical characteristics. A three-storey building founded on nine pad footings is used to assess the reliability of various site investigation scopes and test methods. The pad footings are designed on the basis of settlement, and are examined using 3D finite element analysis and Schmertmann's method. It is observed, as expected, that the likelihood of underdesigning or overdesigning a footing decreases as the scope of the investigation increases. The relationship between these likelihoods and the variability of the ground is presented.

Towards reliable and effective site investigations

It is widely appreciated that, in civil engineering and building projects, the largest element of financial and technical risk usually lies in the ground. Almost exclusively, the scope of geotechnical investigations is governed not by what is needed to characterise the subsurface conditions appropriately but, rather, by how much the client and project manager are willing to spend. There is often little correlation between the variability of the ground and the scope of the investigation. This paper presents the results of a Monte Carlo simulation incorporating many 3D single-layer soil profiles with different statistical characteristics. A three-storey building founded on nine pad footings is used to assess the reliability of various site investigation scopes and test methods. The pad footings are designed on the basis of settlement, and are examined using 3D finite element analysis and Schmertmann's method. It is observed, as expected, that the likelihood of underdesigning or overdesigning a footing decreases as the scope of the investigation increases. The relationship between these likelihoods and the variability of the ground is presented.

Characterization and pilot‐scale studies for chemical oxidation remediation of fractured shale

AbstractThe distribution of volatile organic compounds (VOCs) in fractured shale overlain by thin (< 10 feet) overburden at the Watervliet Arsenal near Albany, New York, was initially determined by sampling water from the fracture network using packer systems in boreholes and also using conventional monitoring wells. Furthermore, short‐term pumping and injection tests were conducted and the boreholes were logged using a variety of geophysical and hydrophysical tools. Tetrachloroethene is the dominant VOC in the groundwater, with lesser concentrations of trichloroethene and degradation products (cis‐1,2‐dichloroethene, trans‐1,2‐dichloroethene, and vinyl chloride). The vertical VOC distributions in the rock matrix were obtained from continuous‐cored holes from which small rock samples, collected at many depths between 18 and 150 feet below ground surface, were analyzed. The rock core VOC concentrations were determined by methanol extraction of crushed rock followed by direct methanol injection onto a gas chromatograph and subsequent estimation of rock porewater VOC concentrations. The rock core data support the concept that diffusion‐driven mass transfer has caused nearly all the VOC mass initially present in the fractures to now reside in the rock matrix, which has a porosity three or four orders of magnitude larger than the bulk fracture porosity. The results of the site characterization indicate that an effective site investigation strategy in fractured shale must include characterization of both the fracture and matrix contaminant distribution. These results also indicate that the most favorable remediation technologies for this fractured shale are those that will destroy VOCs in the rock matrix, particularly contaminants in the sorbed phase, and also destroy the VOC mass in the fractures including both dissolved and immiscible phases. The site characterization resulted in the selection of potassium permanganate for an in situ chemical oxidation pilot study. © 2004 Wiley Periodicals, Inc.

GIS-based information flow in a land-use zoning review process

This work describes a geographical information system (GIS)-based information flow for a land-use zoning review process. GIS technology is employed not only to edit and display maps as conventional GIS applications, but also to enhance work quality. These enhancements include an exploration of hidden information, the production of tentative zoning maps, recognizing potentially problematic areas, conducting crucial site investigations, facilitating informative public hearing, and presenting potential policies. In the case of the Yang–Ming–Shan (YMS) National Park, Taiwan, a GIS-based information flow is employed to assist in the land-use zoning review process. This GIS-based information system reveals several features including: (1) a new, more complicated and effective information flow; (2) close coordination of computing and noncomputing sub-processes; (3) prior identification of over and under-regulated areas to avoid potential appeals and conflicts; (4) economical and effective site investigations, and (5) potential policies established for both private and public land. The case of the YMS National Park is encouraging. We believe that the application of a GIS-based information flow is beneficial to both the zoning plan production and the review process.