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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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    Investigation of the effect of petrological contents on the engineering properties of carbonates aggregates

    Kamani M.Ajalloeian R.
    12页
    查看更多>>摘要：Rock aggregates have widespread applications in construction projects, and their engineering properties play a key role in their application. Aggregate's engineering properties are affected by their inherited petrographic characteristics. In this paper, the impact of various petrographic characteristics on the engineering properties of crushed limestone is evaluated. Petrographic analyses and common quality control aggregate tests were performed on 25 carbonate rock samples. The engineering tests conducted include Los Angeles abrasion value (LAAV), aggregate crushing value (ACV), slake durability index (SDI), magnesium sulfate soundness (SS), and water absorption (WA). Also, the petrographic analyses performed on thin sections involved calculating the percentage of fossil grains (FG), non-fossil grains (NFG), meso-scale porosity and voids (LP), micro-scale porosity and voids (SP), micrite (M), sparite (S), dolomitic grains and cement (D), quartz and chert (Q), clay (C), and opaque minerals (O). Statistical analyses were applied to the dataset to evaluate the correlation and obtain the possible relationships between aggregates engineering and petrographic properties. The results indicated that C, LP, O, and SP have an important effect on the engineering properties of carbonate aggregates. Multiple regression analyses were conducted and R2 values higher than 0.84 were obtained, except for the SS. These equations were evaluated by using various data obtained from scientific resources, and their error values were calculated. The error analysis proved the accuracy of the obtained equations. To investigate the quality of each sample according to allowable limit values, based on international standards, real and estimated values were used. Results proved that selecting the most important petrographical parameters for predicting aggregates engineering properties is quite simple and efficient and can be used in the preliminary stages of aggregate evaluations.
      原文链接:
    • NSTL
    • Elsevier

    The fabric evaluation of two Indian bentonites subjected to different suctions and consolidation pressures

    Jadda K.Bag R.
    15页
    查看更多>>摘要：The study highlighted the fabric evaluation (i.e., pore size distribution (PSD) and morphology) of monovalent and divalent Indian bentonites, subjected to different suctions and consolidation pressures. Oedometer tests were conducted on bentonites specimens in two different initial conditions, i.e., slurry and compacted conditions. The slurry and compacted specimens were prepared at water contents equal to liquid limit (LL) and optimum moisture content (OMC), respectively. The water retention properties of the bentonites were determined in both unconfined (slurry) and confined (compacted) conditions using pressure plate apparatus and WP4C dew-point potentiameter. The influence of different consolidation pressures and suctions on pore structure and morphology of the bentonites were investigated by mercury intrusion porosimetry (MIP) and Field Emission Scanning Electron Microscope (FESEM) observations. For both the bentonites, the bimodal pore size distribution was observed over the applied consolidation pressure between 7.2 kPa and 2289.6 kPa in both slurry and compacted specimen conditions. However, an increase in consolidation pressure lead to a significant decrease in macropore volume. The compression index of the bentonites was found to be strongly correlated with a percentage decrease in macropore intruded volume (R2 = 0.91) and total intruded pore volume (R2 = 0.89), however, independent of micropores volume. The FESEM images and MIP results evidenced that for both the bentonites more homogeneous morphology and effective filling of the pores took place in slurry conditions as compared to initially compacted specimens. For the same void ratio, the hydraulic conductivity of slurry specimens was noted to be slightly lower than the compacted specimens. In slurry conditions at suctions below 3 MPa, the water retention capacity of monovalent bentonite was noted to be higher than that of divalent bentonite, whereas the opposite trend was found in compacted conditions. Irrespective of slurry or compacted conditions, the increase in suction lead to the transformation of bimodal PSD into a unimodal pore family for divalent bentonite, whereas trimodal to unimodal PSD was noted for monovalent bentonite in compacted specimens. The initial state (slurry or compacted) and the boundary condition of the specimen, as well as fabric (pore size distribution and morphology) of the bentonites, were found to have a notable influence on the compressibility, hydraulic conductivity and water retention properties.
      原文链接:
    • NSTL
    • Elsevier

    Shear strength of bentonite saturated with saline solutions exhibiting variety of cations

    Xiang G.Ye W.Hu Z.Jalal F.E....
    7页
    查看更多>>摘要：Investigation of saline solutions on the shear strength (SS) of compacted bentonite is desideratum to evaluate the safety of engineered barriers in order to safely dispose of the high-level radioactive waste. Undrained shear experiments were carried out on Na-bentonite saturated with CaCl2, KCl, and NaCl solutions. The stress-strain relationship of all the bentonite samples exhibits strain softening behavior, and the peak stress increases with the increase of the saline solution concentration. The SS of samples in saline solutions at 0.1 mol/L (M) follows the order of NaCl< KCl < CaCl2, whereas, in 0.5 M salt solutions it follows the order of NaCl<CaCl2 < KCl, indicating that the cation exchange process has a major impact on the SS of bentonite. The modified effective stress concept p’ was used to express the SS in various salt solutions based on Mohr-Coulomb criterion. The results further revealed that the solution concentration had minimal effect on the angle of internal friction φ’. In addition, the strength envelope remains the same when samples are saturated with different concentrations of NaCl solution, unlike the samples saturated with KCl and CaCl2. At lower salinity concentration (0.1 M), the SS in CaCl2 solution approaches maximum value because of higher osmotic suction. On the contrary, the SS of bentonite saturated with KCl attains the highest value at high concentration (0.5 M), which is attributed with strong K-linkage and low hydration energy of potassium ion.
      原文链接:
    • NSTL
    • Elsevier

    Improving mechanical behaviour of collapsible soils by grouting clay nanoparticles

    Seiphoori A.Zamanian M.
    11页
    查看更多>>摘要：The primary geotechnical concern of collapsible soils such as loess is their hydromechanical instability. Upon wetting, metastable aggregates disintegrate, leading soil to collapse under the applied load or self-weight. In situ chemical stabilisation, such as grouting, is a favoured option to improve soil mechanical behaviour; however, the low permeability of loess limits the application of permeation grouting in such deposits. Here a new approach is presented based on the injection of dilute suspensions of montmorillonite clay nanoparticles to improve mechanical behaviour of low permeable loess. In addition to clay, the grouting behaviour of an ordinary cement material was evaluated as a typically favoured soil stabiliser. Reconstituted specimens were also prepared by mixing dry clay or cement particles with soil at similar contents and curing time to compare with the grouting method. SEM images were also taken from the cured samples to visualize the soil fabric. Results revealed that clay suspensions feature a high-mobility in the soil medium as well as a remarkable performance in reducing the collapse potential due to: (1) clay effective particle size (～0.25 μm) that facilitates its mobility in soil, and (2) formation of evaporation-driven solid bridges that reinforce the interparticle bonds during post grouting drying. Results encourage the application of clay nanoparticles over cement for an economical and eco-friendly grouting approach to improve the mechanical behaviour of low permeable collapsible soils.
      原文链接:
    • NSTL
    • Elsevier

    Improved coupled Markov chain method for simulating geological uncertainty

    Zhang J.-Z.Zhang D.-M.Huang H.-W.Xue Y.-D....
    13页
    查看更多>>摘要：Geological uncertainty is common in nature due to complex depositional processes as one layer appears to be randomly embedded in neighbouring layers. However, the geo-structures could be significantly affected by the geological uncertainty, often simulated using the coupled Markov chain (CMC) model. The objective of this study is to develop an improved CMC method by enhancing the rationality of determining the horizontal transition probability matrix (HTPM) in the CMC model to simulate complex multi-layer strata based on limited borehole data. This difficulty of determining HTPM is solved by combining the vertical transition count matrix and intermediate horizontal matrix with Walther's law. The effectiveness of this method is evaluated by the artificial HTPM and virtual boreholes. Boreholes collected from Norway are adopted to illustrate the proposed method for HTPM estimation. Estimating the HTPM has been dramatically enhanced for the improved CMC model and is not sensitive to the borehole layout schemes. The error of HTPM between estimated and actual strata is less than 3% for different borehole schemes. A matching rate indicator is defined to evaluate the accuracy of the simulated results. The results show that the proposed method has good performance and robustness. An optimizing design approach for the borehole location and number is presented to minimize the uncertainty of the stratum simulation based on the information entropy.
      原文链接:
    • NSTL
    • Elsevier

    Estimation of land subsidence potential via distributed fiber optic sensing

    Gu K.Shi B.Liu S.Wu J....
    11页
    查看更多>>摘要：Land subsidence is a global phenomenon that derives from natural processes such as auto-compaction and tectonic activity, as well as anthropogenic activities that are exemplified by withdrawal of water, oil or other fluids from the subsurface. Fluid withdrawal-induced subsidence has become a threat in densely populated zones such as coastal areas, especially in this era of growing climate change impacts when hydrological changes may not enable sufficient recharge of aquifers to replenish withdrawn water. It is important to estimate settlement for design of counter-measures: a challenge in areas of complex sedimentary history and geomedia stratification. Herein is presented the methodology and results of configuration of the Logistics Model using measured settlement data to predict future settlement in the coastal town of Tianjin, P.R. China with validation using continuous strata deformation data obtained through borehole distributed fiber-optic sensing. The cumulative subsidence over the October 2017-December 2019 period reached 56 mm with an estimated potential limit of 96 mm, leaving a balance of 42.0% of the total for attainment in the future. Subsidence of the area is estimated to reach the “stability subsidence stage” by 2050. In the G06 borehole depth range of 3.4–18.4 m which comprises clayey silty sand and silty fine sand, the measured deformation accounts for 58.5% of the total while the residual (future) deformation is 37.6% of that total. The depth ranges of 0–3.4 m (shallow stratum) and 18.4–38.4 m (deep stratum) constitute the “priority layer” because the strata are still in the “accelerated subsidence stage” that is characterized by high subsidence rate estimates for the future. Thus, the projected high subsidence rates of the two layers warrant the design and implementation of proactive countermeasures.
      原文链接:
    • NSTL
    • Elsevier

    Floodplain evolution and its influence on liquefaction clustering: The case study of March 2021 Thessaly, Greece, seismic sequence

    Papathanassiou G.Stampolidis A.Valkaniotis S.Ganas A....
    18页
    查看更多>>摘要：The March 2021 Thessaly, Central Greece, seismic sequence characterized by an Mw = 6.3 mainshock and five Mw > 5.0 aftershocks triggered extensive liquefaction in the floodplain of the Piniada Valley and localized phenomena along the riverbanks of the Titarissios River. In order to document these secondary effects, we carried out immediate post event surveys based on remote sensing techniques and field-based reconnaissance. The initial desktop-based approach succeeded in delineating in advance the extensive liquefaction surface manifestations and in saving time for the subsequent field survey. The field work was performed with ground-based surveys, and UAV aerial campaigns. The longest reported linear liquefaction feature was 26.7 m, while the total sand blow covered an area of 0.0325 km2. Over one of the liquefaction manifestations, we performed parallel 2D electrical resistivity tomography profiles in order to reconstruct the subsoil stratigraphy. The produced 3D resistivity model successfully detects and illustrates the subsurface disruption following the generation of liquefaction. From the comparison between the spatial distribution of liquefaction phenomena and the geomorphological conditions in the area, the direct influence of the historical evolution of Pinios River in clustering liquefaction phenomena was highlighted. Thus, it is confirmed that a detailed investigation of the historical and late Holocene evolution of a floodplain i.e., location of ox-bow lakes, meanders and former river channels, can identify sites prone to liquefaction. This could result in a reduction of the area where detailed engineering geology investigations (e.g., boreholes with in-situ tests) are required for the evaluation of the liquefaction hazard.
      原文链接:
    • NSTL
    • Elsevier

    Uncertainty of heterogeneous hydrogeological models in groundwater flow and land subsidence simulations – A case study in Huwei Town, Taiwan

    Tran D.-H.Wang S.-J.Nguyen Q.C.
    16页
    查看更多>>摘要：The distribution of hydrogeological materials in a three-dimensional heterogeneous aquifer system has a large effect on groundwater flow and land subsidence simulations. The hydrogeological information for regions between boreholes embeds a large amount of uncertainty into the hydrogeological model, and thus affects numerical assessment. Quantifying the effects of the heterogeneous system and hydrogeological model uncertainty on groundwater flow and land subsidence simulations is thus important. Here, data from 46 geological boreholes in Huwei Town, Taiwan, were adopted to investigate hydrogeological model uncertainty. The one-dimensional continuous-lag Markov chain and the geostatistical method were used to analyze the spatial characteristics of hydrogeological materials and generate realizations of the hydrogeological model based on the assessment results. Estimated hydrological conditions and hydraulic parameters were applied to mitigate uncertainty not caused by the hydrogeological model. The mean of the results of land subsidence in Monte Carlo simulations showed a more stable distribution than that of individual realizations, for which land subsidence might be far from the mean. Therefore, the mean and variance results provide a reliable assessment with uncertainty information for land subsidence simulations. The coefficient of variation (CV) was used to quantify the hydrogeological model uncertainty. The CV value of land subsidence was larger than that of the hydraulic head because the thickness of clay is not uniform whereas the flow pattern is smooth. The variance and CV distributions of the hydraulic head and land subsidence provide uncertainty information that can be used to guide site investigations. A heterogeneous hydrogeological model with uncertainty quantification should be carefully applied to land subsidence simulations to obtain reasonable results.
      原文链接:
    • NSTL
    • Elsevier

    A comparative study of different machine learning methods for reservoir landslide displacement prediction

    Wang Y.Wen T.Tang H.Zhang J....
    12页
    查看更多>>摘要：This paper compares the performance of five popular machine learning methods, namely, particle swarm optimization–extreme learning machine (PSO–ELM), particle swarm optimization–kernel extreme learning machine (PSO–KELM), particle swarm optimization–support vector machine (PSO–SVM), particle swarm optimization–least squares support vector machine (PSO–LSSVM), and long short-term memory neural network (LSTM), in the prediction of reservoir landslide displacement. The Baishuihe, Shuping, and Baijiabao landslides in the Three Gorges reservoir area of China were used for case studies. Cumulative displacement was decomposed into trend displacement and periodic displacement by the Hodrick–Prescott filter. The double exponential smoothing method and the five machine learning methods were used to predict the trend and periodic displacement, respectively. The five machine learning methods are compared in three aspects: highest single prediction accuracy, mean prediction accuracy, and prediction stability. The results show that no method performed the best for all three aspects in the three landslide cases. LSTM and PSO–ELM achieved better single prediction accuracy, but worse mean prediction accuracy and stability. PSO–KELM, PSO–LSSVM, and PSO–SVM always yielded consistent predictions with slight variations. On the whole, PSO–KELM and PSO–LSSVM are recommended for their superior mean prediction accuracy and prediction stability.
      原文链接:
    • NSTL
    • Elsevier

    Comprehensive analysis and numerical simulation of a large debris flow in the Meilong catchment, China

    Yang W.Fan T.An H.Ouyang C....
    13页
    查看更多>>摘要：On June 17, 2020, a large debris flow occurred in the Meilong catchment following a short-duration, high-intensity rainstorm. The debris flow was initiated by two shallow landsides upstream of the catchment and had a volume of approximately 7.7 × 105 m3. It blocked the river and then induced flooding, causing significant losses to the local residents. In this study, through a combination of field observation, image interpretation, and laboratory experiments, the initiation mechanism, erosion depth along the main channel, and deposition area of this debris flow were comprehensively analyzed. A sequentially integrated numerical model considering the rainfall interception by vegetation, infiltration, and runoff process was developed. Considering the spatial variations in the climatic, hydrological, and geotechnical parameters, the entire process of debris flow initiation, motion, entrainment, and deposition was simulated. The computational outcomes matched well with the field observation results. A combination of the proposed integrated model and spatially varying parameters can be used to effectively describe the debris flow characteristics in the initiation and propagation stages and provide significant insights into the physical processes involved in such hazards.
      原文链接:
    • NSTL
    • Elsevier