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Engineering Geology
Elsevier Science B.V.
Engineering Geology

Elsevier Science B.V.

0013-7952

Engineering Geology/Journal Engineering GeologySCIISTPEIAHCI
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    Space-time susceptibility modeling of hydro-morphological processes at the Chinese national scale

    Wang N.Cheng W.Xiong J.Marconcini M....
    19页
    查看更多>>摘要：? 2022 The AuthorsHydro-morphological processes (HMP; any process in the spectrum between debris flows and flash floods) threaten human lives and infrastructure; and their effects are only expected to worsen under the influence of climate change. Limiting the potential damage of HMPs by taking preventive or remedial actions requires the probabilistic expectation of where and how frequently these processes may occur. The information on where and how frequently a given earth surface process may manifest can be expressed via susceptibility modeling. For the whole Chinese territory, a susceptibility model for HMP is currently not available. To address this issue, we propose a yearly space-time model built on the basis of a binomial Generalized Linear Model. The target variable of such model is the annual presences/absences of HMP per catchment across China, from 1985 to 2015. This information has been accessed via the Chinese catalogue of HMP, a data repository the Chinese Government has activated in 1950 and which is still currently in use. This binary spatio-temporal information is regressed against a set of time-invariant (catchment shape indices and geomorphic attributes) and time-variant (urban coverage, rainfall, vegetation density and land use) covariates. Furthermore, we include a regression constant for each of the 31 years under consideration and also a three-years aggregated information on previously occurred (and not-occurred) HMP. We consider two versions of our modeling approach, an explanatory benchmark where we fit the whole space-time HMP data, including a multiple intercept per year. Furthermore, we also extend this explanatory model into a predictive one, by considering four temporal cross-validation schemes. As a result, we portrayed the annual susceptibility models into 30 maps, where the south-east of China is shown to exhibit the largest variation in the spatio-temporal probability of HMP occurrence. Also, we compressed the whole spatio-temporal prediction into three summary maps. These report the mean, maximum and 95% confidence interval of the spatio-temporal susceptibility distribution per catchment, per year. The information we present has a dual value. On the one hand, we provide a platform to interpret environmental effects controlling the occurrence of HMP over a very large spatial (the whole Chinese country) and temporal (31 years of records) domain. On the other hand, we provide information on which catchments are more prone to experience a HMP-driven hazard. Hence, a step further would be to select the most susceptible catchments for detailed analysis where physically-based models could be tested to estimate the potentially impacted areas. For transparency, the results generated in this work are shared in the supplementary material as GIS (geopackage) files.
      原文链接:
    • NSTL
    • Elsevier

    Characteristic comparison of seepage-driven and buoyancy-driven landslides in Three Gorges Reservoir area, China

    Zhou C.Cao Y.Yin K.Wu L....
    13页
    查看更多>>摘要：? 2022The Three Gorges Hydropower Station is the largest hydropower station worldwide with the impoundment of the 660-km long reservoir. More than 500 landslides have been triggered by the reservoir water level fluctuation since the first impoundment in 2003. The classification of the reservoir affected landslide (seepage-driven and buoyancy-driven landslides) is crucial for landslide early warning and risk management. There are still no classification criteria for the reservoir landslide in TGRA. In this study, based on the long term in-situ monitoring, numerical simulation and field investigation methods, two typical reservoir landslide of Tangjiao landslide (seepage-driven) and Tanjiahe landslide (buoyancy-driven) in TGRA were taken as study cases. The comparative analysis of the response relationship between the long term deformation and the influencing factors were carried out. It can be found that the intensive deformation of Tangjiao landslide occurred during the rapid drawdown period of the reservoir water level, while Tanjiahe landslide has been deforming in the whole water year. Moreover, by analyzing the cumulative displacement curve, the permeability of the sliding mass, and the sliding surface of six reservoir landslides in TGRA, the classification criteria for seepage-driven and buoyancy-driven landslides in TGRA were proposed.
      原文链接:
    • NSTL
    • Elsevier

    Influence of fines on the monotonic and cyclic shear behaviour of volcanic soil “Shirasu”

    Wu Y.Hyodo T.Hyodo M.
    18页
    查看更多>>摘要：? 2022 Elsevier B.V.Drained and undrained monotonic and undrained cyclic triaxial tests have been carried out on reconstituted samples of Shirasu originally deposited from pyroclastic flows in the Kagoshima area, Japan. This material contains 20%–30% fines derived from the same minerals as the coarse grains. Well-graded fines can form a weakly interlocked structure in loose Shirasu separating the coarse grains and resulting in a weak liquefiable soil. In order to clarify the mechanical characteristics of Shirasu, a series of triaxial tests were carried out on the original Shirasu and a material whose fines had been washed out. The “fines” Shirasu was weak with its properties highly dependent on the confining stress while the “no-fines” Shirasu had a high strength which decreased with increasing confining stress due to breakage of asperities. The presence of fines between coarse grains altered the location of critical state line of Shirasu. Under undrained cyclic loading and low confining pressures, the weakly interlocked structure of medium-dense “fines” Shirasu collapsed resulting in contractive behaviour and liquefaction. As the confining pressure was increased, this weak fine structure was compressed and the soil structure became stiffer under cyclic loading. In practical terms, this means that Shirasu which is placed as a loose hydraulic fill will be prone to liquefaction. The undrained cyclic response of medium-dense “no-fines” Shirasu was similar to that of dense “fines” Shirasu. Thus, the removal of fines was equivalent to compacting the material to a relatively high density.
      原文链接:
    • NSTL
    • Elsevier

    Effect of water contents and initial crack lengths on mechanical properties and failure modes of pre-cracked compacted clay under uniaxial compression

    Shimbo T.Shinzo C.Uchii U.Itto R....
    16页
    查看更多>>摘要：? 2022 Elsevier B.V.This study investigated the effect of different water contents (w) and initial crack lengths on the mechanical properties (i.e., the unconfined compressive strength (UCS), deformation modulus, and mode II fracture toughness (KIIC)) and failure modes of pre-cracked compacted clay under uniaxial compression. In this study, 44 intact specimens and 72 pre-cracked specimens with different water contents (18%, 23%, and 28%) and initial crack lengths (0, 15 and 20 mm at 45°, i.e., the angle at which the maximum shear stress acts on the initial crack surface). The results showed that the UCS decreased with a long initial crack or high-water content. In contrast, the deformation modulus depends on water contents, but not on the initial crack length. KIIC was calculated. It was found to depend on the water content. Empirical correlation formulas between KIIC vs. w and KIIC vs. UCS were obtained. Furthermore, the failure modes of the compacted clay were classified into five types. In some specimens, wing cracks propagating from the initial crack disappeared due to contact and gliding of the crack surface by the shear stress, and only secondary cracks were observed at failure.
      原文链接:
    • NSTL
    • Elsevier

    Seismic response of stratified rock slopes due to incident P and SV waves using a semi-analytical approach

    Wu M.Liu F.Yang J.
    18页
    查看更多>>摘要：? 2022 Elsevier B.V.Based on the theory of elastodynamics and the concept of wave-field separation, a semi-analytical method for the scattering and diffraction of P-SV waves by stratified rock slopes is proposed in this study. The total wave fields are decomposed into the free field with no irregularity and the scattered wave field generated by slope topography. The former is solved directly with the aid of a dynamic stiffness matrix, and the latter is modeled by applying the inclined and horizontal fictitious distributed loads on the corresponding boundaries. Since the methodology is derived from the exact wave equations and the non-singular frequency-domain Green's functions, it can be applied to seismic dynamic response problems for layered slopes with arbitrary incident waves and layer thicknesses, and the presented solutions are high-precision and well-converged. Using a Ricker wavelet as input, the accuracy and effectiveness of the proposed method for both vertically and obliquely incident P and SV waves are fully verified. Taking three actual earthquake records including Taft wave, El Centro wave, and Loma Prieta wave as inputs, several analysis examples are presented. The parametric studies demonstrate that a significant elevation amplification effect can be seen in the ground motion of rock slopes due to the interaction of the upper slope feature with the underlying bedrock half-space. The PGA amplification factor, Fourier spectrum and standard spectral ratio of rock slopes are evidently affected by the slope height, slope angle and shear velocity of the medium. Subsequently, sensitivity analyses are performed on model slopes with varying incident wave frequencies and incident angles to illustrate the broad applicability of the proposed method. Finally, a case study is presented to evaluate the practicality of the presented procedure and highlight the benefits of performing a rapid semi-analytical solution to assess potential hazards of earthquake-induced rock slides.
      原文链接:
    • NSTL
    • Elsevier

    Practical classification of geotechnically complex formations with block-in-matrix fabrics

    Napoli M.L.Barbero M.Festa A.
    14页
    查看更多>>摘要：? 2022The terms “bimrocks”, “bimsoils” and “soil-rock mixtures” indicate different and very common types of geological units with a block-in-matrix fabric that are also “geotechnically complex formations” and are characterized by an internal heterogeneity, and spatial variability of mechanical parameters and lithological compositions. Due to this internal complexity, the understanding of their geomechanical behavior presents a key challenge in geotechnical engineering. However, the lack of a standardized and clear terminology complicates the discrimination of different types of complex formations and their internal mechanical properties, which leads to inconsistency in the literature and research studies. This inconsistency causes misunderstandings, with possible practical implications for the characterization, analysis, design and construction of engineering works. By a combination of geological and geotechnical observations, we propose a new classification for geotechnically complex formations, with particular attention to those with a block-in-matrix internal fabric. Four properties are at the base of this new classification and have a primary role in controlling the geotechnical behavior of block-in-matrix units (bimunits): (i) the composition (i.e., lithology, degree of lithification/consolidation, nature, and rheology) of blocks and the matrix that affects the water sensitivity, (ii) the degree of internal anisotropy (DA) of the block-in-matrix fabric, (iii) the degree of stratal disruption and mixing, and (iv) the volumetric block proportion (VPB). As a result, we classified bimunits in those with “anisotropic”, “isotropic”, and “mixed” (i.e., different behavior depending on the DA of the matrix) textures and, each of these types, into block-in-matrix rocks and block-in-matrix soils (bimrocks and bimsoils in the following). According to the water sensitivity of the matrix, bimrocks are also differentiated into “hard” and “soft”. The novelty of the classification is that it is not limited to few types of geotechnically complex formations (e.g., flysch) but it can be easily applied to all field-based investigations of the different types of complex formations, regardless of their internal degree of stratal disruption, composition, and mechanical response to water sensitivity.
      原文链接:
    • NSTL
    • Elsevier

    Nonlinear site response at liquefiable sites: Insights from downhole seismic observations

    Zhan W.Chen Q.
    16页
    查看更多>>摘要：? 2022 Elsevier B.V.The nonlinear behavior of shallow soil plays an important role in modifying surface ground motions. We analyze the nonlinear site response at liquefiable sites using the compiled long-term ground motion data (ranging from 1992 to 2020 with over 2000 earthquake events) at four high-quality downhole arrays that have liquefied during at least one earthquake. Two nonlinear event parameters, the percentage of nonlinearity (PNL) and the frequency shift parameter (fsp), are used to quantify the modification of site response of strong events to that of weak events. Site-specific regression analyses are performed to correlate nonlinear event parameters to incident motion parameters. Results indicate that site response at liquefiable sites varies from linear to nonlinear to liquefied states as the incident motion intensity changes, and the occurrence of liquefaction could enhance the amplification of low-frequency and very-high-frequency ground motions. As strong-motion observations for liquefiable sites are very limited, the findings of this work are of significance for further study of strong-motion seismology at liquefiable sites.
      原文链接:
    • NSTL
    • Elsevier

    Application of petrophysical relationships to electrical resistivity models for assessing the stability of a landslide in British Columbia, Canada

    Holmes J.Chambers J.Wilkinson P.Meldrum P....
    16页
    查看更多>>摘要：? 2021Landslides in the Thompson River Valley, British Columbia, Canada, threaten the serviceability of two railway lines that connect Vancouver to the rest of Canada and the US. To minimise the impact of slope instability on vital transport infrastructure, as well as on terrestrial and aquatic ecosystems, public safety, communities, local heritage, and the economy, and to better inform decision making, there is a need for monitoring. Since 2013, the Ripley Landslide – a small, slow-moving, translational landslide – has been the focus of monitoring efforts in the Thompson River Valley transportation corridor. In November 2017, a novel Electrical Resistivity Tomography (ERT) monitoring system was installed on the site, providing near-real-time data collection via a telemetric link. 4-Dimensional resistivity models are presented in the context of moisture content and soil suction, two parameters known to influence slope stability in the Thompson River Valley. Here, we discuss the development of laboratory-based petrophysical relationships that relate electrical resistivity to moisture content and soil suction directly, building on relationships developed in the field. The 4-D ERT models were calibrated using these petrophysical relationships to provide insights into the complex spatial and temporal variations in moisture content and soil suction. This study highlights the utility of geoelectrical monitoring for assessing slope stability in the context of moisture-driven landslides.
      原文链接:
    • NSTL
    • Elsevier

    Scale-dependent rock surface characterization using LiDAR surveys

    Aubertin J.D.Hutchinson D.J.
    16页
    查看更多>>摘要：? 2022Evaluating topographical roughness along exposed rock surfaces is to a large extent subjective to the intended application and the related measurement scale. In tunneling and mining applications, topographical roughness of rock surfaces is a key factor in assessing the performance of extractive processes such as blasting backbreak, haulage surface condition and excavation geometry. The scale used to measure surface roughness should be “fit for purpose”, both in terms of the scale of the measurements and the scale required for the practical interpretation. This paper presents a scale-dependent method to characterize the overall surface roughness of rock, from 3D point clouds of rock surfaces collected using terrestrial laser scanner (LiDAR) surveys. A power law formulation is used to quantify the overall surface roughness as a function of the scale of measurement. The proposed methodology is described in detail and applied to different operational settings at two underground mines to evaluate various aspects of the extraction processes. Special consideration is given to the scale dependency of the power law relationship describing the main trend for the overall surface roughness, and how this can be linked to the evaluation of specific excavation processes.
      原文链接:
    • NSTL
    • Elsevier

    Automatic classification and mapping of the seabed using airborne LiDAR bathymetry

    Janowski L.Wroblewski R.Rucinska M.Kubowicz-Grajewska A....
    25页
    查看更多>>摘要：? 2022 The AuthorsShallow coastal areas are among the most inhabited areas and are valuable for biodiversity, recreation and the economy. Due to climate change and sea level rise, sustainable management of coastal areas involves extensive exploration, monitoring, and protection. Current high-resolution remote sensing methods for monitoring these areas include bathymetric LiDAR. Therefore, this study presents a novel methodological approach to assess the suitability of Airborne LiDAR Bathymetry for automatic classification and mapping of the seafloor. Nine classes of geomorphological bedforms and three classes of anthropogenic structures were identified. They were automatically mapped by Geographic Object-Based Image Analysis and machine learning supervised classifiers. The developed method was applied to six study sites and a 48 km submerged coastal zone in the Southern Baltic, achieving an overall accuracy of up to 94%. This study shows that calculation of the Multiresolution Index of Ridge Top Flatness (secondary feature) can be used to quickly and automatically determine sandbar crests and ridge tops. The methodical approach developed in this study can help evaluate and protect other shallow coastal environments and coastal protection structures.
      原文链接:
    • NSTL
    • Elsevier