bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of engineering characteristics of red sand in Luanda, Angola
Authors: Xia Yuyun , Qiao Jianwei , Liu Zhenghong , Tang Lijun , Liu Min , Cheng Yongxiang , Jiang Wen , Huang Lei
Published: May 2024

Red sand is widely distributed on the west coast of Africa, south of the Sahara, and is an essential material for local engineering construction. Red sand possesses orthostasis and high sensitivity to water, exhibiting characteristics that are different from ordinary sandy soil. Laboratory and in-situ tests were conducted to assess its engineering characteristics, including collapsibility, shear characteristics, and bearing capacity. The water sensitivity of red sand was analyzed along with the images from a scanning electron microscope. The findings indicate that red sand can be classified as silty sand. It demonstrates strong collapsibility, with the collapsibility coefficient decreasing as water content increases. The critical water content for red sand to avoid collapsibility is 13%. The shear strength, internal friction angle, and cohesion of undisturbed and remolded red sand decrease with increasing water content. The critical water content for red sand to lose cohesion is 13%. The bearing capacity and deformation modulus of red sand decrease with increasing water content. Red sand exhibits a softening property, with a softening coefficient of 0.4. The water sensitivity of red sand can be attributed to the cementing effects of fine-grained clay minerals adhering to the surface of large particles or aggregating at particle contacts.
Multiphysics simulation of freezing and thawing granular media using material point method
Authors: Yu Jidu , Zhao Jidong , Zhao Shiwei , Liang Weijian
Published: May 2024

In this paper, a fully coupled thermo-hydro-mechanical material point method, applicable to liquid-saturated porous systems undergoing large deformations and phase transitions, is presented. A mathematical framework was established based on multiphasic mixture theory and fundamental physical conservation laws, rather than using phenomenological or semi-empirical equations. A fractional-step-based semi-implicit solution scheme was proposed to solve the coupled formulations within the framework of the generalized interpolation material point method. The proposed method was validated using several benchmark examples, including the talik closure and thaw consolidation. Its performance in simulating climate-driven large deformation problems was further demonstrated by simulating the settlement of a rigid footing on thawing ground. This paper presents an innovative and rigorous framework for predicting the impact of climate change on engineering practices.
Investigation of the effect of loading pulses on the ballast resilient modulus with SmartRock in a large-scale triaxial test
Authors: Huang Shihao , Qian Yu
Published: May 2024

Ballast resilient modulus is a key metric for assessing track resiliency and guiding railroad maintenance. Large-scale triaxial tests are used to determine the ballast resilient modulus and mechanical properties. Replicating complex train-induced loading pulses from field observations in a laboratory setting is challenging owing to technical limitations. Consequently, laboratory tests often employ simplified half-sine and haversine loading pulses with various rest intervals to simulate real-world conditions. However, the effects of different pulses on the obtained ballast resilient modulus remain unclear. In this study, large-scale triaxial tests were conducted using SmartRock sensors to investigate the effects of various cyclic loading pulses on the resilient modulus of the railroad ballast. A new index, called the cyclic loading duration ratio (CLDR), was introduced to categorize these pulses. The results revealed that the resilient modulus correlated with the CLDR, with its impact contingent upon the deviator stress. A CLDR value of 0.20 emerged as a critical threshold, yielding the lowest resilient modulus. Values below this threshold resulted in an increased resilient modulus owing to the consequential large axial acceleration. This study provides insights into the micromechanical resilience reactions of railroad ballast under diverse loading pulses and offers guidance for pulse selection in triaxial testing.
Application of fluid rheology models for milled woody biomass and non-recyclable municipal solid waste particles
Authors: Ikbarieh Abdallah , Lu Yimin , Zhao Yumeng , Dai Sheng
Published: May 2024

Biofuels from biomass and non-recyclable municipal solid waste (N-MSW) can potentially replace aviation fossil fuels. However, the cost-effectiveness is impeded by feedstock handling issues, such as unstable flow or jamming in hoppers and feeders. This issue can be solved mainly based on enhanced understanding of the rheology of biomass and N-MSW particles, which remains poorly understood. Leveraging discrete and continuum-based granular rheology models, in this study, we conduct industry-scale hopper flow testing of milled woody biomass, paper, cardboard, foam, thin film, and plastic particles, and investigate the potential of using fluid rheology models to characterize the hopper flow behavior. The hopper flow tests demonstrate different flow behaviors of tested materials, including fast flow, stable-to-unstable flow, and varying flow rates. Numerical simulation of hopper flow tests utilizing the Gudehus-Bauer hypoplastic model demonstrates good agreement with experimental data for the biomass and rigid plastic particles, and those using non-Newtonian fluid models exhibit promising agreement with experimental data with low computational cost. However, new fluid rheological models are required to capture the unstable and varying rate flows of highly compressible particles such as paper and foam. This study advances the knowledge on the rheology of particulate biomass and N-MSW materials for biofuel production.
Effects of slope topography on rock avalanche mobility and deposition: A 2-D discrete element method investigation
Authors: Xia Jiacheng , Jing Lu , Chen Jianfeng , Peng Ming
Published: May 2024

The impact of rock avalanches is a major concern in mountain areas. However, fundamental understanding and reliable prediction of the depositional area of rock avalanches remains inadequate. Here, an idealized numerical study of granular materials flowing down a slope is carried out using two-dimensional (2-D) discrete element method simulations. The effects of the slope geometry on the mobility and deposit morphology of the granular flow are studied in detail. It is found that the granular flow mobility increases with the curvature radius of the circular ramp, leading to a longer runout distance, which is explained from the viewpoint of energy transfer and dissipation. The results are expected to enhance understanding of the travel and deposition mechanisms of rock avalanches and other related geophysical flows.
Triggering and evolution of static liquefaction in submarine slopes with quasi-saturated sand
Authors: Tong S J , Huang M S , Shi Z H , Shen K M , Wang B
Published: May 2024

Liquefaction flow slides of submarine slopes with quasi-saturated sand have been frequently observed in engineering practice. That instability can be attributed to a decrease in resistant shear strength caused by static liquefaction. However, the triggering of static liquefaction in submarine slopes has received limited attention. To address this gap, a state-dependent constitutive model for quasi-saturated sand with entrapped air is employed that can represent the effects of compression and dissolution of gas accurately. Moreover, the soil model enables the evaluation of the triggering of static liquefaction based on second-order work. To study the triggering mechanism of static liquefaction, a submarine slope model is established using the material point method. The static liquefaction area is detected by the vanish of second-order work. Results indicate that static liquefaction initially arises at the slope surface and gradually expands towards the interior of the slope as the rapid loading at the top of the slope increases. Furthermore, the presence of entrapped gas within the slope can effectively enhance the resistance to slope instability caused by static liquefaction. It significantly alters both the location where static liquefaction is initially triggered and the subsequent evolution pattern, in comparison with saturated submarine slopes.
A review and evaluation of thermal conductivity model of compacted bentonite and its mixture
Authors: Ye W M , Shao C Y , Chen L
Published: May 2024

The thermal conductivity of bentonite plays a crucial role in analyzing the heat transfer process and determining the temperature field distribution within deep geological repositories. Despite considerable efforts in modeling the thermal conductivity of compacted bentonite and its mixtures, a comprehensive synthesis of these studies has not been previously undertaken. This research aimed to thoroughly review predictive models for the thermal conductivity of compacted bentonite and its mixtures, assessing their performance against a substantial dataset comprising 495 measurements of GMZ and MX80 bentonite. Through a systematic compilation and evaluation of seven models for compacted bentonite and three models for bentonite mixtures, the study identified TC2008 and LC2016 as the most accurate models for GMZ and MX80 compacted bentonite, respectively, whereas PT2021 emerged as the superior predictor for GMZ and MX80 bentonite mixtures. This exploration revealed the absence of a single, universally accurate model capable of predicting the thermal conductivities across all bentonite variants, highlighting the necessity for researchers to judiciously select the most fitting model for predicting the thermal conductivity of bentonite. Furthermore, we expressed the inherent limitations in current thermal conductivity models for compacted bentonite and its mixtures, and proposed directions for future inquiry in this domain.
Experimental study on compression behaviours of compacted sandy loam using a Modified State Surface Approach
Authors: Li Yixin , Cui Yujun , Geng Xueyu
Published: May 2024

It is essential to study the deformation of unsaturated soil to predict the settlement of constructed embankments and foundations under precipitation and external loadings. This study conducted suction-controlled and stress-controlled oedometer tests on compacted sandy loam. The void ratio and degree of saturation were measured to study the deformation behaviours of unsaturated soil. The acquired data were analyzed using a modified state surface approach (MSSA). It was found that for the samples with an identical initial state, a unique state surface can be employed to describe the change of void ratio in an e-σ
v’-s space, which consists of an elastic session and a plastic collapsible session. After yielding, the LC yield curve expands along the plastic collapsible surface with increasing loading or decreased suction, accompanied by irrecoverable plastic deformation. Along the hydraulic wetting paths (suction decreasing), the soil exhibits expansive deformation in the elastic surface but collapses into plastic collapsible after yielding. Differing from deformation behaviours, this study also demonstrated that the degree of saturation (S
r) cannot be plotted in a unique surface in S
r-σ
v’-s space regarding hydraulic wetting and mechanical compression. This can be interpreted by different mechanisms of increasing S
r by adsorbing water and mechanical compression.
Structural, soil-water, and dynamic characteristics of clay with different moisture and temperature histories
Authors: Zhang Lin , Han Zhong , Zou Weilie , Feng Huaiping
Published: May 2024

Variations in the hydro-mechanical properties of pavement subgrade soils are complex under long-term, repeated, and interlaced moisture and temperature (M-T) effects, such as wetting-drying (WD) and freeze-thaw (FT) processes. This study compares the soil structure, soil-water characteristic curves, and accumulated plastic strain (ɛ
p) of compacted Heilongjiang clay with three different M-T histories. Experimental results demonstrated that (i) after M-T actions, structural pores develop while textural pores shrink, leading to a reduction in the water retention capacity and an increase in the desaturation rate. Following the stabilization of the M-T effects, the soil structure and soil-water characteristics of specimens with different M-T histories become similar; (ii) at high moisture content (w), ɛ
p is more sensitive to moisture changes (including w and suction, s). Following the FT cycles, ε
p and ε
pa (the difference between the ε
p at 5000th and 3000th cyclic loading) become more sensitive to moisture changes; (iii) after M-T effects, the ε
pa-w relationship is nonlinear while the ε
pa-logs relationship is linear. Different M-T histories generated differences in only the ε
p at the beginning of the FT processes while such differences disappear after M-T effects have stabilized. The experimental data presented in this paper could prove valuable in understanding the behaviors of pavement soils under complex environmental conditions.
Study on rock energy evolution and constitutive model under water–rock interaction
Authors: Zhang H , Liu X L , Huang Z , Lu X L
Published: May 2024

To explore the degradation in rock mechanical properties due to water–rock interactions and formulate a nonlinear damage constitutive model for the entire stress–strain curve of rocks, experiments involving saturated, dry-wet cycling, and uniaxial compression tests were conducted on granite and siltstone. Based on energy theory, the energy evolution of the rock throughout the testing process was scrutinized. The range of the compaction stage was identified through the analysis of the dissipation energy change curve. A nonlinear damage constitutive model for rocks subjected to water-rock interactions was then devised, drawing on concepts from statistical damage mechanics. The findings indicated a progressive reduction in uniaxial compressive strength and elastic modulus due to water–rock interactions, while the Poisson’s ratio was observed to increase. The energy density curve under these conditions delineated four distinct phases: compaction energy dissipation, linear energy accumulation, pre-peak gradient increase, and post-peak sudden change. The introduction of the unit elastic strain energy density metric underscored the deteriorating effects from an energy standpoint. A nonlinear damage constitutive model, incorporating the compaction stage based on a coupled damage variable, was formulated. The predictions of this model closely matched the empirical data, thereby affirming its validity. This model provides an enhanced depiction of rock deformation and failure mechanisms under the influence of water–rock interactions.
Tunnel rockbursts induced by dynamic disturbances: mechanism and mitigation
Authors: Deng Jian , Gong Fengqiang , Zhu Hehua
Published: May 2024

Rockbursts are characterized by violent rock fractures and pose a significant threat to hard-rock tunnels, potentially resulting in casualties and damage to excavation spaces. Globally recognized as one of the least understood and most feared challenges in underground excavations, rockbursts are often triggered by dynamic disturbances such as engineering activities or nearby vibrations. This study conceptualizes rockbursts as dynamic buckling or instability issues inherent in rock structures. It specifically investigates the mechanism of tunnel rockbursts induced by ambient blasting. The derivation of the governing equation of motion, which incorporates shear deformation and rotary inertia of the rock column, results in coupled Mathieu equations. By employing the proposed numerical method, the conditions triggering rockburst were established using instability diagrams. The study examines the effects of static components, dynamic loading, and frequency on a tunnel example, revealing that the amplitude and frequency of dynamic disturbances are critical in influencing the occurrence of tunnel rockbursts through perturbation effects and parametric resonance mechanisms. These insights offer valuable understanding into the mechanisms, mitigation, and control of tunnel rockbursts.
Meta-contact analysis based on contact theory in three-dimensional discontinuous deformation analysis
Authors: Wang Xi , Wu Wei , Zhu Hehua
Published: May 2024

Accurate contact analysis between nonspherical blocks, such as polyhedral blocks, is crucial for modeling jointed rock masses. The Contact Theory provides a rigorous foundation for contact detection. However, designing a robust and efficient algorithm that conforms to the original Contact Theory remains challenging. This study introduces the meta-contact concept for polyhedral blocks, which corresponds to the contact cover on the entrance block of the Contact Theory. Using the meta-contact concept, contact type identification, determination of contact points and plans, and contact force calculation can be formulated while retaining the advantages of Contact Theory in dealing with irregular blocks with small edges and large penetration.
Numerical research method of rock slope with intermittent fractures based on parallel bond contact model
Authors: Yang Hongwei , Zhao Cheng , Xing Jinquan , Hu Tairan , Huang Lin , Chen Huiguan , Pan Haoyu
Published: May 2024

Within the domain of rock slopes characterized by intermittent fracturing, the fracture distribution and the mechanical properties of the interstitial rock bridges significantly influence the stability of the slope. The parallel bond contact model is advantageous in replicating the mechanical behavior of rock particles. This research introduces a numerical methodology for analyzing rock slopes with intermittent fractures using the parallel bond contact model. Initially, the model’s microscale parameters are refined through calibration with empirical data derived from macroscopic mechanical tests on rocks. Following this, the discrete element modeling software is employed to construct a detailed rock slope model. This model incorporates a smooth joint approach to define the intermittent fractures, enabling the creation of slope models with varying configurations of coplanar rock bridges and diverse rock types. The research methodologically investigates the mechanical properties and failure patterns of rock slopes under a spectrum of variable combinations. The findings reveal that slopes with multiple rock bridges demonstrate progressive failure and interlocking phenomena during their load-deformation cycles. These insights provide a foundational understanding for the analysis of catastrophic mechanisms and the stability assessment of rock slopes.
Prediction of the Skid Resistance of Recycled Hot Mix Asphalt Mixture
Authors: Jitsangiam Peerapong , Nusit Korakod , Chidburee Polpreecha , Subsomboon Kumpon , Tanratanawong Sirichai , Innu Sungplon , Sedthayutthaphong Nathanyawat
Published: May 2024

Typically, the skid resistance of pavement surfaces is used to indicate road safety levels. The initial value and long-term behavior of skid resistance can be reportedly determined by modulating asphalt mixture properties during their mix design process. In this study, a skid-resistance prediction equation for recycled asphalt concrete was formulated based on ANOVA test results. An accelerated polishing device was used to replicate the abrasion encountered by road surfaces owing to vehicle–tire interactions for characterizing the skid resistance of recycled asphalt concrete. Notably, key parameters, including initial and terminal values and reduction rate of skid resistance induced by vehicle-related abrasion, were determined. These findings suggest that the initial values and reduction rate of skid resistance can be estimated from the mixed binder properties and initial MTD value. However, the final/terminal skid resistance predicted using aggregate gradations has a limited degree of confidence. To further improve the accuracy of the prediction equation, additional data collection and validation tests are required. In addition, field tests using recycled asphalt concrete are necessary to refine the accuracy and precision of the prediction equations for practical road construction scenarios. This study represents a significant step toward the development of safe and effective road infrastructure.
Centrifuge model test study on consolidation characteristics of soft soil base with drainage pile in highway widening
Authors: Yao X , Chen T , Zhang G
Published: May 2024

In recent years, the widening of existing highways has emerged as a prominent focal point in highway construction. However, uneven settlement often occurs when highways are widened, which sometimes leads to the cracking of pavements, particularly, on a soft soil foundation. Drainage piles have been used to strengthen soft soils by reducing settlement and accelerating drainage consolidation. However, the drainage effect on the consolidation characteristics of drainage piles is still unclear. In this paper, a series of centrifuge model tests were conducted to study the consolidation characteristics of soft soil fixed with drainage piles in highway widening. The test results show that an obvious settlement exists in the old embankment shoulder, whereas a smaller settlement occur near the embankment axis and below the toe of the new embankment. In comparison with the ordinary pile and drainage board, the drainage piles hasten the settlement process of the soil foundation, indicating that drainage piles can significantly accelerate the consolidation of the soft soil foundation.
Evaluating different geogrid products for modulus improvement with bender element sensor technology
Authors: Wang H , Kang M , Kim Y , Qamhia I , Tutumluer E , Shoup H
Published: May 2024

Geogrids extend pavement lifespans by stiffening the unbound aggregate base/subbase through geogrid-aggregate interlocking and restraining of the lateral movements of aggregates. Different geogrids may provide different mechanisms of stabilization based on aggregate size and shape distributions, geogrid properties, and the stabilization mechanism. This study proposed the experimental results of evaluating five different geogrid products: three extruded, one woven, and one welded, with different physical properties tested using a dense graded crushed limestone base course aggregate material. The direct and quantitative stiffness measurements were performed using shear wave transducers (bender elements (BEs)). Small strain shear modulus was measured using three BE sensor pairs instrumented on 300 mm height and 150 mm diameter cylindrical specimens with geogrids installed at specimen midheight. The aggregate material was used based on its as-received gradation. Geogrid-stabilized and unstabilized control tests were conducted in repeated triaxial loading at the 15 stress states following the AASHTO T 307 resilient modulus test protocol. Although the resilient modulus tests could not differentiate the effects of geogrid stabilized specimens, local measurements of small strain shear modulus using the BE sensor pairs demonstrated certain increases in shear moduli owing to the incorporation geogrids. Thus, BE sensor technology was demonstrated as an effective tool for quantifying stiffening/stabilization of different geogrids through increased small strain shear modulus.
Seismic response of tripod suction bucket foundation for offshore wind turbine considering multidirectional earthquake loads
Authors: Wang Yikang , Liang Fayun , Zhang Hao , Yuan Zhouchi
Published: May 2024

Tripod suction buckets offer several advantages as offshore wind turbine (OWT) foundations, including cost-effective installation, high stability, and resistance to overturning. In seismically active regions, OWTs experience horizontal and vertical directions seismic excitations. This study employed an advanced three-dimensional nonlinear finite element analysis to investigate the influence of vertical seismic motions on the dynamic behavior of tripod bucket foundations installed in nonhomogeneous clay deposits. By adopting a simple kinematic hardening model to capture the foundation-soil nonlinear dynamic interaction, parametric analyses were conducted to study the effect of vertical seismic motions, considering several earthquake types and undrained shear strengths of the clay deposit. The results show that the influence of the vertical seismic motion on the dynamic response and deformation of the nacelle depends on the dominant frequency of the vertical seismic motion and the overturning resistance capacity of the OWT in different horizontal directions. The deformation mechanisms of an OWT vary with the strengths of the clay deposits. Based on these analyses, this study offers insights into the influence of vertical seismic motions on the dynamic response of tripod suction bucket foundations.
Augmented dataset for multidimensional ballast segmentation and evaluation
Authors: Ding K , Luo J , Huang H , Hart J M , Qamhia I I A , Tutumluer E
Published: May 2024

Ballast plays an important role as a railway track supporting structure against repeated loading. Ballast degradation results in poor drainage, lateral instability, excessive settlement, service interruptions, and safety concerns. Therefore, utilizing efficient methods for evaluating ballast fouling is important to ensure safe railroad operations. Emerging computer vision approaches have been effectively incorporated into the ballast inspection processes to enhance their accuracy and robustness. Owing to the inherent data-driven nature of deep learning approaches, the efficacy of the developed model heavily depends on the quality of the training dataset, revealing an urgent need for a comprehensive and high-quality annotated ballast aggregate dataset. In this study, a multidimensional ballast aggregate dataset has been established which contains realistic data collected from field and laboratory setups, augmented by data produced by a synthetic ballast particle generator. In the dataset, the 2D data comprised ballast images with 2D annotations (masks) for localizing the particles in the images. The 3D data comprises height maps, point clouds, and 3D annotations for particle localization. The collected data included various environmental lighting levels and fouling conditions to ensure adequate coverage and diversity in the training dataset. A 2D ballast particle segmentation model previously developed by the authors was trained using an augmented dataset and demonstrated reliable and accurate results in field ballast inspections. The proposed dataset will be utilized in future studies, including 3D ballast particle segmentation and shape completion, to aid in the inspection and investigative methods for effective ballast maintenance.
Investigating the influence of excitation force on compaction behavior of gravel in granular blends through DEM simulation
Authors: Ismail A S , Nie Z , Ahmad A , Ali S
Published: May 2024

During the construction of subgrades, the compaction of granular blends is typically achieved through vibrational techniques at varying the frequencies and excitation forces. This study investigates the impact of excitation forces, within the range of 300-600 kPa, on subgrade compaction by employing the discrete element method (DEM). Calibration tests were conducted to establish the contact parameters for the DEM models, and their reliability was verified via vibration compaction tests. The research further explores the evolution of settlement, particle motion, and contact interactions at both macroscopic and mesoscopic levels as influenced by the excitation forces. Furthermore, the influence of excitation force on the stability of skeleton frameworks was analyzed. The results indicated that the number of contacts in the final state increased consistently with the excitation force, leading to a more uniform distribution. This change contributes to a time-dependent stability within the skeleton framework, which effectively limits the movement of fine particles in the final stages and diminishes the sliding between the coarse particles. Conversely, in the initial phases, a rise in excitation force increases the stress concentration between the contacts, which increases the sliding damage to the skeleton frameworks and leads to greater compaction deformation.
Probabilistic model for predicting fire casualties in an urban traffic tunnel
Authors: Zhu R , Zhang D M , Huang Z K
Published: May 2024

Fire accidents could result in severe casualties in an urban traffic tunnel due to the concentration of users and narrow space. However, fire casualties could not be easily predicted due to the complicated evacuation environment and uncertainty in personnel distribution. This paper proposes a probabilistic model to predict the fire casualties in an urban traffic tunnel with only natural ventilation, considering the effects of the thermal and carbon monoxide distribution, in addition to the arrangement of various vehicles. First, the general framework of the probabilistic model was put forward and the methods to analyze the fire scenario, evacuation process, casualty criteria, and probability curve were introduced in details. Then, a case study based on a three-lane traffic tunnel was conducted, and the effects of maximum heat release rate on probabilistic curve of fire casualties were discussed. The results showed that the fire casualty increased with the maximum heat release rate. Besides this, when the distance between fire source and evacuation exit was reduced to 150 m, the impact of maximum heat release rate would decrease significantly. This study made notable contributions toward evaluating the personnel loss in tunnel fire and laid a foundation for assessing and improving the resilience of tunnel.
Sensitivity analysis on GPR A-scan data for cavity detection based on area estimation approach
Authors: Kim J. , Nam B.H , Youn H
Published: May 2024

This study aims to determine the optimal range of A-scan data that enables the detection of cavities in reinforced concrete structures using ground-penetrating radar (GPR). GPR is commonly used as a nondestructive testing method for detecting cavities. However, the identification of cavities using B-scan data is challenging when the cavities are obscured by highly reflective objects such as reinforcements. To address this issue, the B-scan data can be substituted with the A-scan data by adopting an area estimation approach. However, this approach requires the determination of the location and range of the A-scan data. In this study, we analyzed GPR A-scan data obtained from a large-scale concrete block with cavities adjacent to a complex reinforcement layout. The location and range were varied to investigate their effects on the accuracy of object detection using the area estimation approach, and an appropriate range was suggested.
Design and application of a new type of hierarchical control device
Authors: Kang X , Xie X
Published: May 2024

To realize coupling between the yielding and partition failure processes, a new hierarchical control device was designed. The new stage control device comprised an internal and external two-stage structure similar to “piston + sleeve.” Under the action of the surrounding rock pressure, primary yielding occurred first, and the cone slid along the inner wall of the yielding sleeve. With an increase in the surrounding rock pressure, secondary yielding occurred, and the tray slid along the outer wall of the yielding sleeve. The device had a simple mechanical structure and exhibited reliable mechanical properties. It had a convenient and rapid installation process, and the load-displacement curve was obtained by laboratory tensile tests. Mechanical test results showed that the device exhibited a clear function of graded pressure yielding, which was consistent with the designed sectional control curve. The results show that the new hierarchical control device exhibited a good control effect on the surrounding rock and is helpful for TBM in realizing fast driving.
Strategy and analysis of the deformation of subway tunnel caused by pre-dewatering under water-rich sand
Authors: Wang L , Liang F , Wang R , Li J , Lei D
Published: May 2024

Pre-dewatering is an essential step in deep foundation pits with water-rich sand, and its impact on the surrounding environment has attracted increasing attention. To study the impact of pre-dewatering on the tunnel, we selected a typical foundation pit project in Shanghai to conduct in situ pre-dewatering tests and comprehensively record the soil stress, horizontal displacement, and tunnel deformation around the foundation pit during pre-dewatering. The data showed a strong correlation between the displacement and stress changes in the surrounding soil and the locations of the pre-dewatered soil layers. Based on the changes in the water-earth pressure and displacement, the deformation mechanism of the adjacent subway tunnel caused by pre-dewatering before foundation pit excavation was analyzed. Combined with existing research results, strategies such as increasing the stiffness of the ground wall, improving the anti-deformation ability of the soil in the passive area, and on-demand dewatering were proposed, and the findings can be used as reference for similar projects.
Experimental Study on the Self-Initiated Static-Dynamic State Transition Mechanism of Strain Rockburst
Authors: Qian Yuan , Zhao Cheng , Xing Jinquan , Sun Zeyuan , Luo Yinfeng , Zhang Boyi
Published: May 2024

During the entire processes of rockburst catastrophe, the self-initiated static-dynamic state transition behaviour is a turning point in the development of strain rockburst from static deformation to dynamic failure. However, its dynamic process and triggering mechanism have not yet received sufficient attention and accurate revelation. This study focuses on the scientific issue, by designing experiment we have successfully achieved the physical simulation of rockburst under quasi-static displacement loading conditions. Then, the static-dynamic state transition process was studied on a millisecond time scale, and rockburst triggering mechanism was investigated from mechanical perspectives. Through experiment, the self-initiated elastic rebound dynamic behaviour of the surrounding rock is discovered and identified as the key to triggering rockburst. Mechanically, this behaviour directly causes an impact load on the burst rock, which can be considered the direct cause of rockburst.
Centrifuge model test of the influence of tunnel excavation with different spacings on existing tunnels
Authors: Chen-jie LI , Bo LI , Cong-an LI , Zhi-peng WANG
Published: May 2024

The continuous development and utilization of underground space has led to an increasing number of short-distance constructions between new and existing tunnels. New tunnel construction affects the surrounding strata and destroys the structure and operation of the adjacent existing tunnel. Therefore, investigating the influence of new tunnels on the deformation of existing tunnels is crucial. Four centrifugal model tests simulating tunnel excavation processes were conducted to study the influence of tunnel excavation with different spacings on existing tunnels. Liquid was drained one section at a time to simulate the formation loss ratio produced by tunnel excavation and unloading during centrifuge operation, which eliminated the error caused by centrifuge shutdown–restart. Test results indicated that new tunnel excavation led to uneven settlement of the existing tunnel, and the settlement of the existing tunnel was greater than that of the two sides. Under the same burying condition of the new tunnel, the smaller the net distance between the new and existing tunnels, the greater the influence on the vertical and horizontal displacement of the existing tunnel, and the smaller the settlement of the ground surface. New tunnel excavation caused tensile stress near the excavation surface of the existing tunnel. A smaller clear distance resulted in a higher tensile stress. The centrifugal model tests provide technical support for tunnel construction and underground space development.
Bidirectional and nested model for numerical simulation and machine learning: a case study of long-term settlement prediction of tunnel
Authors: Guo X Y , Zhang D M , Chen X S
Published: May 2024

Numerical simulation and machine learning are commonly adopted research methods in engineering. This paper proposes a bidirectional and nested model for numerical simulation and machine learning (BNNM). This model permits numerical simulation methods and machine learning methods to participate in each other’s calculation process. It helps overcome the obstruction of unclear mechanisms and inaccurate parameters in numerical simulation methods, and avoid overfitting problem caused by too many features in machine learning methods. Moreover, BNNM frees machine learning methods from the dependence on a specific set of labels. The BNNM helps train machine learning models using obtainable labels, and output results that cannot be easily obtained using field, experiment, and numerical simulations. To illustrate its construction method and performance, a representative BNNM model is constructed using BPNN, in addition to a simple numerical simulation model. This model predicts the long-term settlement of shield tunnel. The results show that the representative model effectively reduces the modelling difficulty associated with numerical simulation and improves prediction accuracy of BPNN model. The model also derives long-term constitutive models of various soils with only the tunnel settlement data set. Although a simplified constitutive model was used, the main advantages of the BNNM model have been highlighted.
A displacement-based method for evaluating the stability of a pile-stabilized slope
Authors: Yu Yang , Lu Pin , Shi Bo , Sun Hongyue
Published: May 2024

This study proposes a theoretical model for evaluating the safety factor of a pile-stabilized slope using the monitored displacement of the sliding layer. The stabilizing force provided by the piles was determined using the subgrade reaction method, with the monitored displacement of the sliding layer as the primary input parameter. The sliding layer of the slope was considered as a rigid body sliding along the slip surface, assumed to be viscous-perfectly plastic with a Mohr–Coulomb failure condition. Based on the proposed model, the real-time safety factor of the slope could be determined using the limit equilibrium method based on the monitored displacement of the sliding layer. The model was applied to the Hongyan landslide to demonstrate its effectiveness. The results indicated that the model could reasonably predict the safety factor, offering practical convenience for engineers.
Deriving an unsaturated hydraulic conductivity function based on ergun equation
Authors: Gong Yufeng , Qian Yu
Published: May 2024

Computational Fluid Dynamics (CFD) is a widely-used numerical technique for simulating flow phenomena, particularly unsaturated flow, which involves two-phase flow. This type of flow can be effectively modeled using the Volume of Fluid (VOF) method. The key to accurately depicting unsaturated flow is the unsaturated hydraulic function (K-function), which connects flow velocity to the hydraulic gradient. However, employing the VOF method alongside the commonly used Ergun equation for modeling porous media can result in an unrealistic K-function. This, in turn, often leads to unrepresentative models of unsaturated flow. This study focuses on determining the equivalent particle diameter, an essential factor in the Ergun equation, and uses this to derive an improved K-function. The modified K-function exhibits promising results, closely matching experimental data and outperforming other empirical methods. This improved function could enhance the description and simulation of unsaturated flows.
Estimation of landslide during heavy rainfall based on FEM-MPM model
Authors: Li X , Ishikawa a T , Zhu Y
Published: May 2024

In 2016, Typhoon No. 10 landed on Hokkaido, Japan and resulted in slope failures near Nissho Pass. The massive precipitation generated serious runoff within the catchment area, which accounted for the slope instability. Besides, the rainfall induced slope instability developed as landslide. However, the traditional slope instability analyses were often finished ignoring the transportation of instable soil. This study conducted soil runout analysis as well as slope instability analysis with a finite element method-material point method (FEM-MPM) model to catch the disaster area. In the slope instability analysis using three-dimensional (3D) FEM model, runoff and infiltration were considered at the same time to evaluate the slope instability during heavy rainfall. Here, the surface flow and subsurface flow were governed by shallow water equation, Richards’s equation and Green-Ampt infiltration capacity model. Then, based on the hydraulic field result, local factor of safety (LFS) distribution and dangerous spots were given by FEM model. Subsequently in the soil runout analysis using two-dimensional (2D) and 3D MPM model, large deformation part after failure and the soil transportation were examined to reveal the amount of soil that is risky to be washed away during heavy rainfall. The simulation results proved the appropriateness of this simulation method to reproduce the slope instability and landslide process during heavy rainfall.
Experimental and numerical investigation on soil erosion under different pipeline-leaking locations
Authors: Wang Z Y , Tan Y , Long Y Y
Published: May 2024

In recent years, cave-in ground failures have become increasingly common worldwide. The leakage of defective pipelines buried below ground level has been identified as a significant contributor to these failures. This study utilized experimental seepage-erosion tests to characterize ground collapses resulting from pipeline leakage and examined the impacts of leakage locations on soil and water losses. Subsequently, discrete element method-finite difference method (DEM-FDM) coupling analyses were conducted to elucidate the mesoscopic mechanisms of pipeline leakage, including changes in seepage force, effective stress, and soil pressure on the pipeline during leakage. The findings include: (1) The locations of leaking spots on pipelines significantly influenced soil and water losses; (2) Leaking spots closer to the pipe bottom led to more severe ground collapses due to larger seepage forces; (3) Soil pressure exhibited decreasing trends near the leaking spot and increasing trends at other locations due to the soil arching effect. These insights provide valuable guidance for preventing pipeline leakages.
GIS-Based assessment of geological hazard susceptibility in Southeastern Tibetan region: An information entropy approach
Authors: Pei Songqi , Zhao Cheng
Published: May 2024

The terrain and geological conditions in southeastern Tibetan region are complex, especially under the influence of hydraulic and hydroelectric development, and susceptibility to geological hazards has increased. This study focused on three counties in Changdu City. We aimed to assess the susceptibility to geological hazards in this region using Geographic Information System (GIS) technology and information entropy models. Historical geological hazard data from the local area, remote sensing data, and GIS were utilized to develop an information entropy model for landslide geological hazard analysis. Key triggering factors for landslide geological hazards in the southeastern Tibetan region were identified, and a comprehensive dataset was compiled. Information entropy model was applied to consider various influencing factors and calculate their impact on geological hazards, Landslide risk in the area was analyzed and generate a susceptibility map for geological hazards. Our results indicate significant correlations between factors, such as steep terrain, human engineering activities, and land types with landslide occurrences. The established evaluation model can reasonably predict potential geological hazard risk in Nujiang River region and partially reflect the distribution characteristics of geological hazards in the southeastern Tibetan region. This offers a scientific foundation for relevant authorities to formulate disaster prevention and response strategies.
Influence of pre-seismic history on the cyclic response of seasonal frozen silty sand
Authors: Fu Hongjian , Ni Xueqian , Zhang Sheng
Published: May 2024

The implementation of the Belt and Road strategy has increased construction activities in regions with seasonally frozen soil, such as the Qinghai–Tibet plateau. Numerous infrastructure systems in the region are built on seasonally frozen soil, rendering them susceptible to high-frequency seismic loads. Previous studies have demonstrated the significant influence of pre-seismic loads on the mechanical responses of soils. However, research on the influence of pre-seismic loads on seasonally frozen soil is limited. Therefore, two groups of cyclic triaxial tests are conducted in this study to investigate the impact of pre-seismic load and freeze-thaw history on the cyclic response of silty sand. Sample reconstitution and freeze-thaw procedures are described in detail. The test results indicate that the cyclic strength of silty sand decreases with the freeze-thaw history, although the influence diminishes with an increase in the number of freeze-thaw cycles. Additionally, a small pre-seismic load enhances the silty-sand strength, regardless of the freeze-thaw history it underwent. The findings of this study offer valuable insights for engineering construction in areas prone to seasonal freezing and earthquakes.
Machine Learning Models for Predicting Shear Wave Velocity of Soils
Authors: Mousavi Z. , Bayat M. , Feng W.
Published: May 2024

As regards regions prone to seismic activity, shear wave velocity (Vs) is a design parameter for geotechnical systems exposed to dynamic loads. Evaluating Vs
for geomaterials involves on-site and laboratory assessments; however, its availability is often limited in projects owing to resource and time constraints. Various mathematical and empirical models have been proposed to predict Vs for cohesive or granular soils; however, a majority of these models are specific to certain soil types and loading conditions. In this study, machine learning techniques were used for Vs
prediction. These models encompass factors such as grading attributes, void ratio (e), mean effective confining pressure (σ’m), consolidation stress ratio (KC), and specimen preparation methods. To achieve this, a series of bender element tests was performed on various sand and gravel mixtures supplemented with culled data from earlier investigations. This study facilitated the development of three machine learning models aimed at predicting the Vs for granular soils: artificial neural networks (ANN), support vector regression (SVR), and gradient boosting regression (GBR), aimed at predicting Vs
for granular soils. The findings of the study demonstrated that the ANN model exhibited enhanced precision and reduced error compared with the other models.