Soils and Foundations最新文献_第4页

Experimental study on the engineering characteristics of expansive soil improved conjointly using enzyme induced carbonate precipitation and eggshell powder

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-02-01 DOI: 10.1016/j.sandf.2025.101567

Mudassir Mehmood , Yuancheng Guo , Yunlong Liu , Lei Wang , Wen Nie , Bantayehu Uba Uge , Sharafat Ali , Chen Xuanyu , Yingao Zhao

Enzyme induced carbonate precipitation (EICP) is gaining more and more recognition that can be utilized on-site to enhance the quality of the weak soil. In this experimental study, a novel approach that combines EICP and eggshell powder (ESP) to strengthen the engineering characteristics of natural expansive soil has been implemented. The engineering properties of expansive soil were examined using the environmentally friendly method EICP with an optimal 0.75 mol/L concentration and 14% ESP optimal content, with varying curing durations. ESP serves as a filler between particles and also a nucleation site to promote the precipitation of calcium carbonate. A thorough examination of the soil’s microstructure development after treatment was additionally executed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The findings demonstrated that combining EICP and ESP decreases the swelling pressure about 25 times, compared with the individual treatment that yielded 5 and 1.5 times reduction for EICP and ESP, respectively. Additionally, the combined treatment led to an increase in the unconfined compressive strength, cohesion, internal friction angle, unsoaked CBR, and soaked CBR by 3, 1.6, 1.8, 8.0, and 9.5 times, respectively, indicating better enhancements than the individual treatments of EICP and ESP. Moreover, at the microstructural level, SEM imagery demonstrated a highly reinforced soil composite. The XRD analysis unveils distinct mineralogical changes, predominantly characterized by enhanced calcite formation and a refined microstructural composition. This study highlights the synergistic potential of combining EICP and ESP as stabilizing additives to enhance the engineering properties of expansive soil. Beyond soil enhancement, this innovative blend offers a sustainable solution by repurposing agrowaste. The mutual incorporation of EICP and ESP emerges as a promising strategy for advancing sustainable civil infrastructure development.

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引用次数: 0

Effectiveness of sheet pile enclosure with drainage ability as liquefaction countermeasure for river levees

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-02-01 DOI: 10.1016/j.sandf.2024.101564

Mitsu Okamura , Mizuki Suyama , Kohei Ono

Sheet-pile enclosures are often employed as liquefaction countermeasures for river levees in Japan. However, the stiffness of the sheet piles alone is often insufficient to maintain levees on liquefied foundation soil high enough to prevent overflooding. Sheet piles with additional members having drainage ability have been developed and employed, which are expected to provide the combined effects of lateral confinement and dissipation of excess pore pressure from the liquefiable soil beneath the levees. In this study, a series of centrifuge tests was conducted to assess the liquefaction-induced settlement of levees and the excess pore pressure generated in sand beds enclosed by sheet piles with and without drainage ability. The effects of the drainage ability were studied for liquefiable foundation soil with a wide range of permeabilities. The results confirmed that the settlement in a sand bed is closely related to the excess pore pressure. Additionally, a practical method was developed for predicting excess pore pressure and then validated through a comparison with test observations. Using this procedure, the effects of the sand-bed geometry, levee height, and severity of the earthquake shaking were studied in relation to the characteristics of the resistance of the sand to liquefaction on the excess pore pressure. Moreover, the applicability of drainage members to a Japanese river levee countermeasure project was analyzed. For practical use in river levee rehabilitation projects, drainage members were confirmed to be more effective for sand with a higher liquefaction-resistance. Owing to the high maximum acceleration of ground motions stipulated in the design code, these drainage members may not be effective for sand with permeabilities in the order of 10⁻⁵ m/s or lower. In addition, the slopes of the liquefaction resistance curves of the sand were observed to significantly affect the effectiveness of the drainage members. Therefore, the liquefaction-resistance curves are considered to be more important than the liquefaction-resistance ratio alone when designing drainage members as a liquefaction countermeasure.

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引用次数: 0

Centrifuge model test study on pile-anchor support system

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-02-01 DOI: 10.1016/j.sandf.2024.101561

Xiaomeng Xue , Ga Zhang

With the increasing development of underground engineering, various support systems of foundation pits are emerging, and the pile-anchor support system is widely used in deep foundation pit engineering construction. A series of centrifuge model tests for foundation pit excavation was conducted to investigate the deformation laws of the retaining pile and the soil for pile-anchor support system. Compared with the test results of cantilever pile support system, the horizontal displacement of the retaining pile and the settlement of the retained soil significantly decreased, as well as the deformation mode of the pile and the horizontal and vertical distribution of the deformation of retained soil were different for the pile-anchor support system. The movement of retained soil tended towards the vertical due to the increasing deformation of the entire pile, further leading to the variations of the displacement distributions of the soil. The anchor limited the deflection of the pile and thus resulted in a significant reduction of soil deformation. The direction of tangential relative displacement of the anchor and soil changed during the development of the pile top displacement. Accordingly, the pile-anchor-soil interaction was categorized into three different states, which were affected by inclination angles of the anchor as well. Furthermore, it is concluded that there was an optimal inclination angle of the anchor by comparing the test results of pile-anchor support system with various inclination angles.

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引用次数: 0

Simulating field grouting to improve the shear strength of consolidated clay by microbially induced carbonate precipitation

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2025-02-01 DOI: 10.1016/j.sandf.2025.101572

Fuchen Teng, Yong Cheng Sie

Soft clay layers in urban areas pose challenges due to low strength and high compressibility, complicating urban construction. Microbially induced carbonate precipitation (MICP) has demonstrated its ability to enhance soil strength in sandy soils. However, research on the utilization of MICP for clay has been limited. Thus, this paper introduced a new method that combines MICP with grouting. The treated MICP solutions were injected into the consolidated clay samples in a triaxial system to simulate the improvement of grouting in the consolidated soil layer in the field. A series of modified triaxial tests, fluorescent nucleic acid stains, solution/soil pH tests, and microscopic observation tests were conducted. Results indicated a 1.7 times increase in soil strength with bioaugmentation treatment on clay under 150 kPa consolidation stress. Additionally, the weight of CaCO₃ increased by 3.2 g, achieving a precipitation ratio of 58 %. The injected bacteria were observed in the bottom-most and center of the sample, confirming their mobility in the clay. The enhancement of shear strength on treated clay involved not only urease-producing bacteria but also environmental chemical reactions and natural bacterial effects. Furthermore, a microstructure changes of MICP in clay was observed, wherein CaCO₃ effectively filled the pore spaces and bonded particles together to enhance strength. Based on the results, through MICP treatment with injection method, consolidated clay enhances its mechanical behavior and microstructural formation to improve the shear strength.

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引用次数: 0

Study on drainage mechanism of complete path for vacuum preloading based on thermodynamics theory 基于热力学理论的真空预压全径排水机理研究

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2024-12-01 DOI: 10.1016/j.sandf.2024.101542

Fu Chen , Aiping Tang

Vacuum preloading has been a widely used consolidation method for soft clay ground improvement since the 1980s. Consolidation theory only explains the radial drainage process from soil to prefabricated vertical drains (PVD); however, the complete drainage path mechanism by which water drains vertically through PVD to the upper horizontal sand drainage layer and eventually to vacuum pumps is still unclear, resulting in controversies about vacuum preloading. A large oedometer test was performed to study the complete drainage-path mechanism for vacuum preloading. During vacuum preloading, the soil’s average internal temperature decreased to 5 °C below initial temperature, with the lowest temperate occurring near the PVD, which was 2 °C lower than the outskirt. A complete drainage path mechanism is proposed based on the phenomenon of internal temperature decreases. Water evaporates only in the PVD, and the vertical movement of water in the PVD is caused by a density difference between the gas molecules that is independent of gravity. Finally, the proposed mechanism was used to explain the controversy about vacuum preloading. For example, vacuum should not decay along the PVD, vacuum acting elevation at the top or bottom of the PVD has no effect on the final vacuum preloading effectiveness, there is no unsaturated zone formed, and the groundwater level does not drop during vacuum preloading.

真空预压是20世纪80年代以来广泛应用的软土地基加固方法。固结理论只解释了从土壤到预制垂直排水管的径向排水过程；然而，水通过PVD垂直排入上部水平排砂层并最终排入真空泵的完整排砂路径机制尚不清楚，导致了真空预压的争议。为了研究真空预压的全排水路径机制，进行了大型排水计试验。在真空预压过程中，土壤内部平均温度比初始温度低5℃，其中PVD附近温度最低，比外围温度低2℃。基于内部温度下降现象，提出了一种完整的排水路径机制。水只在PVD中蒸发，水在PVD中的垂直运动是由独立于重力的气体分子之间的密度差引起的。最后，用提出的机理解释了真空预压存在的争议。真空沿PVD不衰减，PVD顶部和底部的真空作用标高对最终的真空预压效果没有影响，真空预压期间不形成非饱和带，地下水位不下降。

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引用次数: 0

Insights into the mechanics of uncemented and lightly cemented compacted iron ore tailings under high confining pressures 高围压下未胶结和轻度胶结压实铁矿尾矿的力学研究

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2024-12-01 DOI: 10.1016/j.sandf.2024.101543

Nilo Cesar Consoli , Hugo Carlos Scheuermann Filho , Alexia Cindy Wagner , João Vítor de Azambuja Carvalho , João Pedro Camelo Guedes , Inácio Carvalho , Bruno Guimarães Delgado , João Paulo de Sousa Silva

Grading changes due to particle breakage are crucial in geotechnical engineering problems involving high pressures, such as elevated-height dry stacking facilities for compacted filtered iron ore tailings disposal. However, understanding the iron ore tailings response at high stress is still in its early stages in the Brazilian context. It is now marked by the increasing need for alternatives to tailings allocation rather than the traditional slurry disposal in impoundments. The present research, which examines the mechanical response of iron ore tailings and lightly cemented iron ore tailings over confining pressures ranging from 1.2 to 120 MPa for dry stacking purposes, provides significant insights into this area. The study relied on triaxial tests conducted on a high-pressure apparatus that employed specimens compacted at three different compaction degrees. The cement addition incurred slight differences in isotropic compression, enlarging the range of achievable states. Still, the shearing response of both uncemented and lightly cemented tailings was very similar, particularly at higher stress levels, resulting in an equivalent critical state locus. In the v- ln ṕ plane, an S-shaped function described the critical state and delineated the regions where particle breakage becomes an important source of volumetric strain. In brief, this study provides novel insights into the behaviour of uncemented and lightly cemented iron ore tailings in the context of elevated-height dry stacking facilities.

在涉及高压的岩土工程问题中，颗粒破碎引起的级配变化是至关重要的，例如用于压实过滤铁矿尾矿处置的高架干堆设施。然而，在巴西，对高应力下铁矿尾矿响应的了解仍处于早期阶段。现在的特点是越来越需要替代尾矿分配，而不是传统的在蓄水池中处置矿浆。本研究考察了铁矿尾矿和轻胶结铁矿尾矿在1.2 - 120 MPa干堆围压下的力学响应，为这一领域提供了重要见解。该研究依赖于高压装置上进行的三轴试验，该装置采用了三种不同压实程度的样品。水泥的加入对各向同性压缩产生了轻微的影响，扩大了可达到状态的范围。然而，未胶结和轻度胶结尾矿的剪切响应非常相似，特别是在较高的应力水平下，导致等效的临界状态轨迹。在v- ln ṕ平面上，一个s形函数描述了临界状态，并描绘了颗粒破碎成为体积应变重要来源的区域。简而言之，本研究为高架干堆设施中未胶结和轻度胶结铁矿尾矿的行为提供了新的见解。

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引用次数: 0

Wellbore stability research based on transversely isotropic strength criteria in shale formation 基于页岩层横向各向同性强度标准的井筒稳定性研究

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2024-11-21 DOI: 10.1016/j.sandf.2024.101541

Xiangsen Gao , Min Wang , Xian Shi , Peng Dai , Mingming Zhang

Borehole instability is a significant concern when drilling inclined wells through bedding layers. Traditional drilling techniques have encountered various challenges due to shale’s tendency to shear and slide along faults, joints, and weak planes. This study explores the mechanisms behind borehole instability in layered shale formations by conducting triaxial compression experiments on shale samples with varying bedding angles. It examines the anisotropic nature of shale properties and how strength varies with bedding angle. By integrating anisotropic strength criteria and transversely isotropic stress models around wells, the study develops a predictive model for borehole instability in layered shale formations and assesses the impact of different anisotropic strength criteria on predicting collapse pressures. The results show that shale’s elastic modulus and Poisson’s ratio have an inverse relationship with the increasing bedding angle. Besides, the patchy plane of weakness model, characterized by the parameter η, accurately predicts strength during inherent shear failure, sliding along bedding planes, and mixed failure. In contrast, the single plane of weakness model yields the highest collapse pressure predictions, while the Mohr-Coulomb criterion provides the lowest. The patchy plane of weakness model offers intermediate and more realistic pressure predictions. Moreover, while the type of in-situ stress does not affect the magnitude of collapse pressure, it influences the distribution characteristics of the collapse pressure cloud map. These findings, which account for shale anisotropy in minimum mud pressure analysis, have the potential to enhance drilling efficiency in practical applications.

在通过垫层钻斜井时，井眼不稳定性是一个重要问题。由于页岩具有沿断层、节理和薄弱平面剪切和滑动的倾向，传统钻井技术遇到了各种挑战。本研究通过对不同层理角度的页岩样本进行三轴压缩实验，探索层状页岩层井眼失稳背后的机理。研究探讨了页岩特性的各向异性，以及强度如何随层理角度变化。通过整合各向异性强度标准和油井周围的横向各向同性应力模型，该研究建立了层状页岩层井眼失稳的预测模型，并评估了不同各向异性强度标准对预测坍塌压力的影响。结果表明，页岩的弹性模量和泊松比与层理角的增大呈反比关系。此外，以参数 η 为特征的薄弱面斑块模型能准确预测固有剪切破坏、沿基底面滑动和混合破坏时的强度。相比之下，单一薄弱面模型预测的塌落压力最高，而莫尔-库仑准则预测的塌落压力最低。斑驳的薄弱平面模型提供的压力预测结果介于两者之间，也更符合实际情况。此外，虽然原位应力的类型不会影响塌陷压力的大小，但会影响塌陷压力云图的分布特征。这些发现在最小泥浆压力分析中考虑了页岩各向异性，有望在实际应用中提高钻井效率。

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引用次数: 0

Efficient reliability analysis of unsaturated slope stability under rapid drawdown using XGBoost-based surrogate model 利用基于 XGBoost 的代用模型对快速缩减条件下的非饱和边坡稳定性进行高效可靠性分析

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2024-11-15 DOI: 10.1016/j.sandf.2024.101539

Wengang Zhang , Bo Ran , Xin Gu , Yanmei Zhang , Yulin Zou , Peiqing Wang

Reservoir slope stability during water level drawdown has drawn increasing concern in geotechnical engineering in recent years. In this study, an efficient reliability analysis framework based on the extreme gradient boosting (XGBoost) surrogate model is employed to evaluate the failure probability of unsaturated slopes subjected to the rapid drawdown considering the depth-dependent properties of spatially varying soils. A c-φ slope is selected as an illustrative example to investigate the coupled influence of the non-stationary characteristic of shear strength parameters and saturated hydraulic conductivity, as well as water level drawdown velocity, maximum drop height and scale of fluctuation on the slope failure probability. Results show that the adopted framework can estimate the low-level probability of slope failure with high accuracy and efficiency. It is found that the velocity and maximum height of water level drawdown have a significant effect on the unsaturated slope stability. Furthermore, it is recommended that the depth-dependent non-stationary soil properties be considered in most cases to ensure a more accurate result.

近年来，水库边坡在水位下降过程中的稳定性越来越受到岩土工程的关注。本研究采用基于极端梯度提升（XGBoost）代用模型的高效可靠性分析框架，来评估非饱和边坡在水位快速下降时的破坏概率，其中考虑了空间变化土壤的深度相关特性。以一个 c-φ 斜坡为例，研究了剪切强度参数和饱和导流系数的非稳态特性以及水位下降速度、最大下降高度和波动规模对斜坡破坏概率的耦合影响。结果表明，所采用的框架可以高精度、高效率地估算边坡崩塌的低级概率。研究发现，水位下降速度和最大下降高度对非饱和边坡稳定性有显著影响。此外，建议在大多数情况下考虑与深度相关的非稳态土壤特性，以确保得出更准确的结果。

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引用次数: 0

Advancement ratio effect on screw pile performance in the bearing layer 推进比对承载层螺旋桩性能的影响

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2024-11-14 DOI: 10.1016/j.sandf.2024.101537

Adnan Anwar Malik , Shekh Istiaq Ahmed , Umair Ali , Syed Kamran Hussain Shah , Jiro Kuwano

The advantages of using screw piles are quite evident nowadays, which enhances its importance in the field of deep foundations. Moreover, the current environmental challenges direct the construction industry towards sustainability, creating more opportunities for such type of piling techniques to be used in the future. Therefore, more investigation is required to optimise screw pile performance in terms of ultimate bearing capacity associated with installation efforts. To explore further, the current study focused on the effect of the advancement ratio on ultimate bearing capacity and work done due to installation load and torque. The model scale of testing is adopted, and two kinds of ground (using Toyoura sand), i.e., scenario I: loose sand over dense sand and scenario II: loose sand, are prepared to install the single helix screw pile. In the case of scenario I, the screw is installed up to 1 times the helix diameter into the dense bearing layer. Based on the experimental results, it was observed that as the advancement ratio (from 0.25 to 1.25) increased, the installation load also increased. On the other hand, the installation torque decreased with the increase in advancement ratio. This was due to the increase in the number of rotations per pitch penetration and the resultant movement of sand particles. The change in the state of the ground around the screw pile is strongly related to the advancement ratio and initial density. The ideal advancement ratio (1.0) is difficult to attain in the field due to high pressing load demand; empirical equations are developed, which can be used to estimate the increase/decrease of ultimate bearing capacity and associated installation requirements in terms of work done for the initial design stage.

如今，使用螺旋桩的优势非常明显，这提高了其在深基础领域的重要性。此外，当前的环境挑战将建筑行业引向可持续发展的方向，这为未来使用此类打桩技术创造了更多机会。因此，需要进行更多研究，以优化螺旋桩在与安装工作相关的极限承载力方面的性能。为了进一步探索，本次研究重点关注了推进比对最终承载力以及安装荷载和扭矩所做功的影响。试验采用模型比例，准备了两种地面（使用丰浦砂）来安装单螺旋式螺旋桩，即情况 I：松散砂覆盖密集砂和情况 II：松散砂。在情况 I 中，螺旋安装到 1 倍螺旋直径的致密承载层中。实验结果表明，随着推进比（从 0.25 到 1.25）的增加，安装载荷也随之增加。另一方面，安装扭矩随着推进比的增加而减小。这是由于每个螺距插入的旋转次数增加以及由此产生的沙粒移动所致。螺旋桩周围地面状态的变化与推进比和初始密度密切相关。理想的推进比（1.0）在现场很难达到，因为压载需求很高；我们开发了经验公式，可用于估算极限承载力的增加/减少以及初始设计阶段所需的相关安装工作量。

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引用次数: 0

Spatial earth pressure analysis of clayey fill behind retaining wall in V-shaped gully terrain V 型沟谷地形中挡土墙后粘土填料的空间土压力分析

IF 3.3 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

Soils and Foundations

Pub Date : 2024-11-13 DOI: 10.1016/j.sandf.2024.101538

Yun Que , Jisong Zhang , Yu Tian , Xiaosong Li

Mountain road construction often involves crossing numerous ravine terrains. To ensure road safety, numerous shoulder retaining walls are built to stabilize the roadbed. However, the limitations imposed by gullies result in significant spatial effects on the soil pressure distribution behind the walls, rendering traditional two-dimensional soil pressure theories inadequate. To investigate the spatial distribution of active earth pressure on clayey fill behind the walls, this paper presents a three-dimensional theoretical solution for earth pressure on V-type retaining walls in gully terrains, using theoretical analysis and numerical simulation. The results indicate that the clayey fill causes a slip crack behind the wall, forming a tension crack region with zero earth pressure, the depth of which increases with the fill’s cohesive force. Additionally, the earth pressure distribution behind the V-type retaining wall exhibits a significant spatial effect, being “larger in the middle and smaller at the ends” along the wall’s width. Compared to traditional two-dimensional theories, the earth pressure predicted by this spatial theory is lower, and the resultant force location is higher, and the overturning resistance in region III is largest. Therefore, this part should be enhanced in construction design.

山区公路建设往往需要穿越众多峡谷地形。为了确保道路安全，需要修建大量路肩挡土墙来稳定路基。然而，由于沟壑的限制，墙后的土压力分布会受到很大的空间影响，使得传统的二维土压力理论无法满足要求。为了研究墙后粘性填土上活动土压力的空间分布，本文采用理论分析和数值模拟的方法，提出了沟谷地形中 V 型挡土墙土压力的三维理论解。结果表明，粘土填料会在墙后造成滑移裂缝，形成土压力为零的拉伸裂缝区域，裂缝深度随填料内聚力的增加而增加。此外，V 型挡土墙后的土压力分布具有明显的空间效应，沿墙宽 "中间大，两端小"。与传统的二维理论相比，该空间理论预测的土压力较低，所产生的力位置较高，且区域 III 的抗倾覆能力最大。因此，在施工设计中应加强这一部分的设计。

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引用次数: 0