International Journal of Geo-Engineering最新文献

Marl soil is highly prone to erosion when exposed to water flow, posing a potential threat to structural stability. The common practice of stabilizing soil involves the addition of cement and lime. However, persistent reports of severe ruptures in many stabilized soils, even after extended periods, have raised concerns. In stabilized marls, unexpected ruptures primarily result from the formation of ettringite, which gradually damages the soil structure. This article aims to assess the impact of nanosilica on the formation of ettringite and the nanostructure of calcium silicate hydrate (C-S-H) during the marl soil stabilization process with lime. To achieve this, marl soil was stabilized with varying percentages of lime and nanosilica. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images were collected to observe changes in mineralogy and microstructural properties. Various geotechnical parameters, including granularity, Atterberg limits, compressive strength, and pH, were measured. The results indicate that the uniform distribution of nanosilica in marl-lime soils enhances pozzolanic activities, calcium aluminate hydrate growth (C-A-H), and the nanostructure of calcium silicate hydrate (C-S-H). According to XRD and SEM experiments, the presence of nanosilica reduces the formation of ettringite. Moreover, the compressive strength of modified samples exhibited an upward trend. In the experimental sample manipulated with 1% nanosilica combined with 6% lime, the compressive strength increased by 1.84 MPa during the initial 7 days, representing an approximately 18-fold improvement compared to the control sample.

This study demonstrates the efficacy of employing Rhizopus oryzae fungus inoculum as a potential solution to improve soil erodibility in coastal environments. A set of unconfined compression tests is conducted on Miami Beach sand treated with a R. oryzae inoculum. Our findings suggest that the R. oryzae fungus inoculum effectively improves the stability of sand by acting as a natural binding agent. This finding aligns with previous studies that utilized different Rhizopus species, such as Rhizopus oligosporus, to improve sand properties. However, a notable difference is observed; the R. oryzae-treated sand exhibits remarkable durability, maintaining significant strength over an extended period without water or dietary supply. The durability is likely attributable to the morphological characteristics of R. oryzae that extensively branches its mycelial network. This paper shares the new discovery to the bio-geotechnics research community, potentially allowing for the customization of soil improvement process by choosing between the fast-acting R. oligosporus and the longer-lasting R. oryzae.

Highway shoulder rocks are exposed to continuous erosion force due to extreme rainfall that could be caused by global warming to some extent. However, the logical design method for erosion-resistant highway shoulder is not well-researched yet. This study utilized a large-scale UNLETB (University of Nebraska Lincoln–Erosion Testing Bed) with a 7.6 cm nozzle width and a 4000 cm³/sec flow rate to study the erosion characteristics of highway shoulder rocks. Test results showed that different shoulder materials currently used had vastly diverse erosion resistance. However, the clear criteria between the erosion-resistant gradation and other gradation could not be determined easily. Then, this study trained ANN (Artificial Neural Network) with test results to conveniently distinguish the erosion resistance of rocks from other rocks. The ANN predicted the acceptable/non-acceptable erosion characteristics of shoulder rocks with close to 99% accuracy based on the three gradation parameters (D₁₀, D₃₀, and D₆₀).

A collection of feed forward neural networks (FNN) for estimating the limit pressure load and the according displacements at limit state of a footing settlement is presented. The training procedure is through supervised learning with error loss function the mean squared error norm. The input dataset is originated from Monte Carlo simulations for a variety of loadings and stochastic uncertainty of the material of the clayey soil domain. The material yield function is the Modified Cam Clay model. The accuracy of the FNN’s is in terms of relative error no more than (10^{-5}) and this applies to all output variables. Furthermore, the epochs of the training of the FNN’s required for construction are found to be small in amount, in the order of magnitude of 90,000, leading to an alleviated data cost and computational expense. The input uncertainty of Karhunen Loeve random field sum appears to provide the most detrimental values for the displacement field of the soil domain. The most unfavorable situation for the displacement field result to limit displacements in the order of magnitude of 0.05 m, that may result to structural collapse if they appear to the founded structure. These series can provide an easy and reliable estimation for the failure of shallow foundation and therefore it can be a useful implement for geotechnical engineering analysis and design.

The development of effective and cost-efficient landfill liners is crucial to prevent groundwater contamination from leachate, safeguarding soil quality and the environment. Composite liners, particularly those combining bentonite with supplementary materials such as fly ash or marble dust, present a promising solution. This study delves into a comprehensive investigation of the physical properties of landfill liners composed of bentonite-fly ash and bentonite-marble dust mixtures through an extensive series of laboratory tests. The research systematically analyzes various proportions of bentonite with fly ash and marble dust, evaluating their impact on liner performance in comparison to Bentonite-sand mixtures. Physicochemical analyses are employed to understand the interactions and behaviors of these distinct substances within the amended bentonite. A wide array of physical properties, including Atterberg’s limits, compaction characteristics, free swell index, modified free swell index, California bearing ratio, cohesion, and angle of internal friction, are meticulously examined. Collectively, these properties offer a comprehensive overview of the suitability and performance potential of bentonite-fly ash and bentonite-marble dust mixtures as landfill liners, presenting a viable alternative to traditional bentonite-sand mixtures. The study reveals synergistic effects between bentonite and both fly ash and marble dust, highlighting their significant contributions to enhancing the physical traits of landfill liners. This advancement in landfill liner design holds the promise of effectively mitigating detrimental environmental impacts associated with waste disposal. While this study provides a robust foundation, it is essential for future investigations to prioritize long-term performance assessments and real-world implementation. Validation and fine-tuning of these findings are crucial to ensuring practical applicability and efficacy within authentic landfill construction scenarios. This holistic approach will contribute to the continued evolution and optimization of landfill liner design, addressing the pressing challenges of sustainable waste management and environmental protection.

The southeast Texas (SETX) coastal area, owing to its unique geographical location and geological attributes, is facing a spectrum of geological challenges, such as ground subsidence, flooding, and coastal erosion. This study endeavors to evaluate the recent instances of ground subsidence and their associated rates, focusing on comprehending their implications for flooding within SETX. Employing the Persistence Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique, this study employs Sentinel-1 SAR satellite data with descending orbit observations spanning from January 2020 to March 2023. Our findings indicate that both the northwestern and eastern regions of Houston have been settled with rates up to 2 cm/year. This settlement trend is consistent with data derived from GPS and groundwater level measurements. This investigation explicitly shows the substantial temporal and spatial variations in subsidence rates, predominantly influenced by localized groundwater extraction due to urbanization (e.g., population growth, land development, etc.). By advocating for the integration of InSAR, GPS, and groundwater measurements, this research aspires to make valuable contributions toward the mitigation of subsidence and flood-related hazards in the SETX area.

Calcium carbonate precipitation using a urease enzyme, referred to herein as Enzyme-Induced Carbonate Precipitation (EICP) is a technique for soil improvement. In this technique, a mixed solution composed of reagents and the urease enzyme, which produces calcite, is utilized as the grouting material. Recently, alternative materials to the urease enzyme have been examined to resolve the cost issue of using the urease enzyme. In this study, several tests were conducted to compare commercial urease and soybean-derived crude urease. A comparison of their hydrolysis rates was done through urease activity tests. The microscopic structures and mineralogy of the precipitated materials, produced during various loading periods, were investigated through SEM and XRD analyses. Moreover, the reinforcing effect of the grouting solutions on the treated soil specimens was evaluated by measuring the unconfined compressive strength (UCS) of the treated samples. Interestingly, the precipitated CaCO₃ was vaterite and calcite when using soybean urease, while it was mostly calcite when using the urease enzyme. Higher UCS values were obtained with the soybean urease samples because the precipitated CaCO₃ seemed to be concentrated at the inter-grain contacts. It was concluded that soybean powder shows great efficacy as a replacement for commercially produced enzyme urease in soil-improvement techniques mediated by carbonate precipitation.

The Peshawar Basin is a part of the lower Himalayas that contains an enormous amount of groundwater storage. The evaluation of groundwater potential in the southern Peshawar district was done using well logging, lithostratigraphic properties, and combined hydrogeological and geophysical techniques. A total of 13 Vertical Electrical Sounding (VES) profiles were utilised to assess potential groundwater zones for surface resistivity studies. The aquifer system was delineated by comparing the data from five boreholes with the VES findings. An exploration of super-saturated groundwater potential was conducted, utilising parameters such as transmissivity (T), hydraulic conductivity (K), storativity, and the Dar Zarrouk analysis. The Dar Zarrouk analysis yielded average values of transverse resistance (TR), longitudinal conductance (S), and anisotropy (λ), which were determined to be 8069.12, 0.51, and 0.561, respectively. Similarly, average values of transmissivity (T), hydraulic conductivity (K), and storativity were obtained, resulting in 28.67, 0.24, and 0.000177, respectively. The saturated confined layer, characterized by highly saturated zones, was identified to begin at a depth of approximately 119 m and extend down to the lower boundary of the aquifer. The examined aquifer is composed of clay, sand, gravel, boulders, and loose layers of lacustrine mud that are interlayered to form an unconsolidated groundwater aquifer system. The aquifers in the region are highly developed and consisted of unconfined, semi-confined, and confined aquifer systems. As a result, it is possible to use the aquifer for groundwater development in the study area because of its low -to-medium discharge.

This study contributes to the quantitative understanding of kaolinite reactions with lime over two years. Unconfined Compressive Strength (UCS) increased linearly with time, doubling within one year, followed by a 14% decrease. Spectroscopic analysis of the system was performed at ten curing times (0, 7, 28, 90, 120, 180, 270, 360, 540 and 720 days) using Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and ²Nuclear Magnetic Resonance (NMR). Both TGA and XRD showed decrease of portlandite up to 180 days; complete consumption appears to have occurred by 270 days. TGA curves indicated an increase in hydration products in the first 360 days which followed a linear trend with UCS increase. No hydration products were observable by either XRD or NMR during that timeframe and no detectable changes in the kaolinite content either. After 360 days, growth in the hydrates in TGA slowed, and XRD, NMR showed a rapid increase of stratlingite (Ca₂Al₂SiO₇∙8H₂O) up to 720 days along with a decrease in the kaolinite signal. Collectively, these results point to two phases in kaolinite dissolution: the first phase, up to about 360 days, is incongruent, characterized by preferential release of Si or Al and portlandite consumption, leading to amorphous Calcium Silicate Hydrate (CSH) or an Afm phase, calcium monosulphoaluminate hydrate (CAH) formation. The second phase involves congruent dissolution and formation of Calcium Alumino Silicate Hydrate (CASH). It is hypothesized that CSH or CAH to CASH transformation occurs in the second stage, causing a disturbance in the cementitious matrix and loss in strength.

While the shear behavior of granular soils is directly related to the microstructure of contacts which often leads to the coaxiality between Cauchy stress and Satake fabric tensors, it is generally accepted by the geomechanics and geotechnical engineering community that the capillary effects are isotropic. At low saturation levels, however, the pore fluid tends to form interparticle menisci that can also manifest an anisotropic structure, which may result in the development of anisotropic capillarity in wetted granular media. To study the interplay between the solid grain contacts and the liquid bridges at the micro-scales, this study adopts a coupled discrete element method that utilizes a linear contact model combined with a capillary model, and explores their effects by conducting a series of numerical experiments. The distributions of contact and capillary force orientations during the experiment are further investigated to better understand how their alignments affect the global response of the granular assembly subjected to a deviatoric loading. The results indicate that the global shear stress response is not only affected by the contact fabric but also by the network of liquid bridges, and we also observe that the particles may lose contact while the pendular menisci may not be destroyed during the elastic unloading.