Research

16 pages, 2696 KiB

Open AccessArticle

Experimental Investigation on the Effect of Salt Solution on the Soil Freezing Characteristic Curve for Expansive Soils

by Haiwen Yu, Fengfu Hao, Panpan Yi, Qin Zhang and Tiantian Ma

Sustainability 2024, 16(1), 363; https://doi.org/10.3390/su16010363 - 30 Dec 2023

Viewed by 725

With the development of the Belt and Road Initiative in China, high-speed railways are booming and inevitably pass through seasonal frost regions. In Nanyang basin, due to seasonal changes, railway subgrades will undergo frost heaving and thawing subsidence. The freezing characteristics of the [...] Read more.

With the development of the Belt and Road Initiative in China, high-speed railways are booming and inevitably pass through seasonal frost regions. In Nanyang basin, due to seasonal changes, railway subgrades will undergo frost heaving and thawing subsidence. The freezing characteristics of the soil are characterized by the freezing characteristic curve, and the important factors affecting the freezing characteristic curve are the content of expansive clay minerals in the soil and the salt solution. Therefore, three soil samples with different montmorillonite contents were saturated with salt solutions of different concentrations, and the freezing temperature of the soil samples was controlled by a cold bath. After the temperature equilibrium, the frozen stable soil samples were put into a nuclear magnetic resonance instrument to test the unfrozen water content, and the relationship between the freezing temperature and the unfrozen water content of expansive soil under different salt solution concentrations was obtained. Additionally, a unified model was used to simulate the test results. The results show that SFCC shifts to the left, that is, the sodium chloride salt solution reduces the freezing point of the soil sample so that it has more unfrozen water at the same temperature. At the same time, the soil’s freezing characteristic curves are closely related to content of expansive clay minerals in the soil. The more expansive clay mineral content, the greater the corresponding unfrozen water content. These results provide some basic insights for improving the frost heave and thaw subsidence problems of railway subgrades in seasonal permafrost regions, which will have a positive impact on promoting the management and rational application of land resources and the promotion of sustainable development. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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14 pages, 4291 KiB

Open AccessArticle

Study of Constitutive Models of Reconstituted Clay with High Initial Water Content

by Jie Liu, Shijun Hu, Gang Liu, Jingbo Zhang and Zheng Lu

Sustainability 2023, 15(16), 12618; https://doi.org/10.3390/su151612618 - 21 Aug 2023

Viewed by 577

Abstract

The compression and shear behavior of reconstituted clay are closely related to the initial water content of the reconstituted soil. It is difficult to obtain the compression and shear test data of clay with a high initial water content. This study aims to [...] Read more.

The compression and shear behavior of reconstituted clay are closely related to the initial water content of the reconstituted soil. It is difficult to obtain the compression and shear test data of clay with a high initial water content. This study aims to propose a model to predict the compression deformation and strength characteristics of reconstituted clay prepared with any initial water content using less data. Based on the concept of the disturbed state, this paper establishes a mathematical model that can simulate the compression and triaxial shear characteristics of reconstituted clay with different initial water contents. This model uses three compression curves of reconstituted clay with different initial water contents to calibrate the model parameters, and can predict the compression deformation characteristics of reconstituted clay prepared with any initial water content. The model can simulate the consolidated undrained shear behavior of clay reconstituted with different initial water contents. Comparing the measured data shows that the model is in good agreement with the measured compression curve and the triaxial stress–strain curve. The error of the predicted pore ratio and test pore ratio before yield is within 5%, and the error of the predicted pore ratio and test pore ratio after yield is within 10%. The stress–strain relationship of clay hardening with different water contents can be captured. The model can provide a preliminary prediction for the mechanical properties of clay with a high initial water content. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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20 pages, 4210 KiB

Open AccessArticle

Risk Assessment of Single-Gully Debris Flow Based on Dynamic Changes in Provenance in the Wenchuan Earthquake Zone: A Case Study of the Qipan Gully

by Na Su, Linrong Xu, Bo Yang, Yongwei Li and Fengyu Gu

Sustainability 2023, 15(15), 12098; https://doi.org/10.3390/su151512098 - 07 Aug 2023

Cited by 1 | Viewed by 1202

Abstract

After the Wenchuan earthquake on 12 May 2008, a huge amount of loose deposits was generated on the mountain surface in the earthquake zone, and vegetation was severely damaged, providing a rich source of material for debris flow, greatly increasing the danger. For [...] Read more.

After the Wenchuan earthquake on 12 May 2008, a huge amount of loose deposits was generated on the mountain surface in the earthquake zone, and vegetation was severely damaged, providing a rich source of material for debris flow, greatly increasing the danger. For many years, researchers have mainly considered the recovery of slope vegetation in assessing the risk of debris flow post-earthquake. However, field investigations have found that large amounts of the dynamic reserve materials in the gully have an important impact on the risk. Thus, based on field survey data, this paper takes the Qipan gully in Wenchuan County as an object and uses multi-source and multi-scale monitoring methods (Landsat series, Quickbird, and Unmanned Air Vehicle) to analyze and statistically study the provenance of the slope and gully both pre- and post- the earthquake. By comprehensively using game theory combination weighting and the cloud model, a dynamic risk assessment model for debris flow was constructed to evaluate the risk of debris flow from 2005 to 2019. The results show that the slope provenance post-earthquake was 7.7 times that of pre-earthquake, and by 2019 the slope provenance had recovered to the pre-earthquake level. Based on the statistical estimation of the amount of debris flow outbreak and the dredging of the blocking dam recorded in relevant data, the dynamic provenance of debris flow had decreased by about 781.3 × 10⁴ m³ by 2019. Compared with considering slope provenance only, the assessment result of debris flow risk considering both slope and gully provenance is more realistic. The results are expected to provide reference and guidance for dynamic assessment of the risk of debris flow faced by increasing projects in high-seismic-intensity mountainous areas and to ensure the safety of people’s lives and property effectively. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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14 pages, 3255 KiB

Open AccessArticle

Predicting the Function of the Dissolution Rate with Depth Using Drilling Data from Shallow Strata at Karst Sites

by Xiaolan Xie, Hailing Li, Gangchen Sun and Xianfa Cao

Sustainability 2023, 15(14), 11191; https://doi.org/10.3390/su151411191 - 18 Jul 2023

Viewed by 685

Abstract

The degree of dissolution in building foundations has been proven to be an exponentially decaying function of depth, which can be characterized by the dissolution rate depth distribution function obtained from survey drilling data. If the dissolution rate depth distribution function can be [...] Read more.

The degree of dissolution in building foundations has been proven to be an exponentially decaying function of depth, which can be characterized by the dissolution rate depth distribution function obtained from survey drilling data. If the dissolution rate depth distribution function can be predicted using shallow drilling data, it would reduce the workload and cost of surveying, and have positive engineering significance. In this study, in the context of the Liuzhou Style Harbor project in Liuzhou City, the dissolution rate depth distribution prediction curve was obtained using drilling data above elevations H₃₀, H₄₀, and H₅₀ (corresponding to dissolution rates of 30%, 40%, and 50%, respectively). The prediction accuracy of the curve was thoroughly analyzed in terms of curve deviation and parameters of the intensive dissolution layer. The conclusion has also been verified by more engineering practices. The results showed that the predicted dissolution rate depth distribution function curve obtained from survey data above elevation H₃₀ was very close to the actual curve, and sometimes matched it. The dissolution rate deviation within the range of the intensive dissolution layer was generally less than 10%, and the deviation in the boundary elevation of the intensive dissolution layer was generally less than 1.0 m. The predicted function was highly reliable, and the prediction deviation met the requirements of engineering practice. Therefore, it is recommended that elevation H₃₀ be used as one of the controlling conditions for the depth of survey drilling in karst building foundation investigations. These research findings can provide a basis for optimizing a karst foundation investigation plan. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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12 pages, 2296 KiB

Open AccessArticle

Effect of Fines Content on Pore Distribution of Sand/Clay Composite Soil

by Mingqiang Wang, Pan Chen, Panpan Yi and Tiantian Ma

Sustainability 2023, 15(12), 9216; https://doi.org/10.3390/su15129216 - 07 Jun 2023

Viewed by 951

Abstract

Plant sand fixation is the most durable and environmentally friendly sand mitigation measure for windblown sand hazards. For aeolian–sand composite soil, the fines content is the main factor affecting the pore size distribution characteristics and determines the soil water retention characteristics. Sandy soil [...] Read more.

Plant sand fixation is the most durable and environmentally friendly sand mitigation measure for windblown sand hazards. For aeolian–sand composite soil, the fines content is the main factor affecting the pore size distribution characteristics and determines the soil water retention characteristics. Sandy soil with uniform particle size was used as the material, low-plasticity clay as a fine particle, and composite soils with different fines content were prepared. The evolution of the pore size distribution of composite soils was quantitatively determined using low-field nuclear magnetic resonance technology, and the influence of the fines content on the pore size distribution was obtained. The results show that as the fines content increases, the pore size first increases and then decreases. The pore size distribution curve gradually changes from a single-peak structure to a double-peak structure and becomes a unimodal structure again. The corresponding dominant pore size of composite soils increases first and then decreases with the increase in the fines content. A critical fine particle content is identified to control the strong local honeycomb pore structure of composite soils, which provides a theoretical basis for the material selection and design of plant sand fixation measures. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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10 pages, 1900 KiB

Open AccessArticle

Study of Ion Adsorption and Shear Strength of Red Clay under Leaching Action

by Yu Song, Hui Li, Yukun Geng, Lulu Xia and Rongtao Yan

Sustainability 2023, 15(2), 959; https://doi.org/10.3390/su15020959 - 04 Jan 2023

Viewed by 1206

Abstract

To study the soil-water effect of red clay, a leaching test is conducted by loading red clay into a soil column and collecting the leaching waste liquid periodically for analysis of the ion content and conductivity changes in the leaching waste liquid. After [...] Read more.

To study the soil-water effect of red clay, a leaching test is conducted by loading red clay into a soil column and collecting the leaching waste liquid periodically for analysis of the ion content and conductivity changes in the leaching waste liquid. After leaching and filtering, the soil is removed from the column and reconstituted as a straight-shear specimen for a straight-shear test. Ca²⁺, Mg²⁺, and SO₄²⁻ ions increased and then stabilized in water samples as leaching time increased, while Na⁺, Cl⁻, and NO₃⁻ declined and then stabilized. Due to their presence in the leaching solution, Ca²⁺, Mg²⁺, and SO₄²⁻ ions are initially adsorbed by the soil and then saturated by adsorption. In contrast, Na⁺, Cl⁻, and NO₃⁻ precipitate out of the soil due to the dissolution and ion exchange of the soil sample, thereby weakening their effects. Consequently, these ions appear to vary in various ways. The relationship between ion content in solution and conductivity has also been discovere, and the conductivity varies with the total ion charge in the solution. The angle of internal friction decreases as the leaching time increases, but the cohesion of the soil increases. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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19 pages, 9195 KiB

Open AccessArticle

Seismicity and Stress State in the Ryukyu Islands Subduction Zone

by Zhuojuan Xie, Enhui Wang and Yuejun Lyu

Sustainability 2022, 14(22), 15146; https://doi.org/10.3390/su142215146 - 15 Nov 2022

Cited by 1 | Viewed by 1709

Abstract

Based on the newly compiled and mostly complete unified earthquake catalogue for China’s seas and adjacent areas, further information was obtained about the structural shape and dip angle of the Benioff zone in the Ryukyu Islands subduction zone during the different subduction stages. [...] Read more.

Based on the newly compiled and mostly complete unified earthquake catalogue for China’s seas and adjacent areas, further information was obtained about the structural shape and dip angle of the Benioff zone in the Ryukyu Islands subduction zone during the different subduction stages. In addition, using the damped regional stress tensor inversion method, we were able to investigate the complex stress field characteristics and the dynamic significance of the shallow and intermediate earthquakes in the Ryukyu Islands subduction zone. The results show that the tectonic stress field of the Ryukyu Islands subduction zone was extensional along the subduction direction in the northern area of the Tokara Strait and was compressional along the subduction direction in the southern area of the Tokara Strait. The R value of the shallow stress field of the Okinawa Trough was low, and the σ₃ was stable in the NNW direction with a small dip angle (>30°). The type of stress field in the shallow part of the Okinawa Trough transitioned from strike-slip type to normal fault type from north to south, reflecting the difference in the degree of development of the trough, and the southern segment of the trough began to transform into the expansion stage. The northeastern portion of the study area and southeast Taiwan constituted the high R value (0.68–0.87) region where the σ₂ had tensile components. The stress state was biaxial tension–uniaxial compression, and the principal compressive stress was determined to be in the SEE direction with a large dip angle (>30°). The σ₁ in northeast Taiwan exhibited a nearly vertical (>60°) plunge, while the σ₂ and σ₃ were nearly horizontal. The σ₂ was thrust in the ENE–WSW direction, and the σ₃ was extended in the NNW direction. Through this research, a greater understanding has been gained of the seismicity characteristics and shape of the Ryukyu Islands subduction zone. Supplementary research has also been completed on the focal mechanism solution and stress field of the Ryukyu Islands subduction zone. Finally, this research is important for earthquake hazard analysis and earthquake engineering safety evaluation in this area. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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12 pages, 3090 KiB

Open AccessArticle

Study of Dynamic Evolution of the Shear Band in Triaxial Soil Samples Using Photogrammetry Technology

by Yi Xia, Chunmei Mu, Wenjie Li, Kai Ye and Haojie Wu

Sustainability 2022, 14(21), 14660; https://doi.org/10.3390/su142114660 - 07 Nov 2022

Cited by 1 | Viewed by 1512

Abstract

In order to avoid the influence of end restraint on triaxial stress and strain measurements, this study combines photogrammetry and computer technology to apply to the unconsolidated undrained test of triaxial soil samples. The novel method can establish an intuitive shear band evolution [...] Read more.

In order to avoid the influence of end restraint on triaxial stress and strain measurements, this study combines photogrammetry and computer technology to apply to the unconsolidated undrained test of triaxial soil samples. The novel method can establish an intuitive shear band evolution model of soil samples and help attain a clear and intuitive shear band evolution law. On the basis of the conventional triaxial test, this new method needs to paste the RAD (Ringed Automatically Detected) code points on the rubber film, plexiglass cover and brackets and then take pictures of the RAD code points in the loading process in a surrounding manner, with which the 3D shape of the restored soil samples can be determined. After eliminating the influence of refraction, the coded point cloud coordinates measured in the experiment can be used to calculate the axial deformation and radial deformation of the soil sample in the deformation process and determine the local stress–strain curve and three-dimensional displacement field diagram of the soil sample. The test shows that the new method can clearly determine the peak value and inflection point of the stress–strain curve in the middle region of soil samples, enabling it to reflect the shear change process of the soil sample more accurately. In addition, the displacement field can be used to directly observe the formation, development and penetration process of the shear band in soil samples. Full article

(This article belongs to the Special Issue Exploration of Marine Geological Resources and Geological Technology)

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