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17 pages, 5641 KiB

Open AccessArticle

Experimental Study on the Strength Characteristics of Cast-In-Situ Mortar Specimens in a Slurry Environment

by Zhijiang Yang, Yulu Chen, Tingting Luo, Tao Han, Chuanwei Jia, Tao Zhang and Weihao Yang

Appl. Sci. 2024, 14(23), 11225; https://doi.org/10.3390/app142311225 - 2 Dec 2024

Viewed by 458

Abstract

As coal resource development progresses deeper underground, the increasing depth of mine shafts poses significant challenges to the safety and stability of traditional shaft construction methods, further compounding operational difficulties. In this context, cast-in-situ concrete shaft walls in a slurry environment have emerged [...] Read more.

As coal resource development progresses deeper underground, the increasing depth of mine shafts poses significant challenges to the safety and stability of traditional shaft construction methods, further compounding operational difficulties. In this context, cast-in-situ concrete shaft walls in a slurry environment have emerged as an effective solution. The strength of these shaft walls is a crucial parameter for assessing their safety. To explore this, experiments were conducted on slurry preparation and mortar casting (used here as a substitute for concrete) under three different conditions: slurry environment, pure water environment, and dry environment. The cast specimens underwent compressive, tensile, shear, and microscopic observation tests to analyze the strength development patterns of the mortar specimens in these varied casting environments. The study yielded several key findings: As the casting environment becomes more complex, the strength of the mortar specimens gradually decreases. Specifically, specimens cast in a slurry environment exhibit strengths approximately 15% to 20% lower than those cast in a dry environment, although both environments show similar trends in strength development over time. Across all casting environments, the initial strength loss of the specimens is significant, while the rate of strength loss decreases in the later stages; the strength loss is minimal in specimens cast in a pure water environment and reaches its maximum in those cast in a slurry environment. Additionally, in specimens cast in a slurry environment, air void diameter tends to polarize, and the distribution of air void is denser compared to the other two environments. In conclusion, cast-in-situ mortar in a slurry environment exhibits the lowest strength and the greatest strength loss compared to specimens cast in dry and pure water environments. Nonetheless, the strength development trends over time remain similar across all conditions, providing theoretical and technical support for the construction of shaft walls in slurry environments. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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36 pages, 18495 KiB

Open AccessArticle

Size-Dependent Mechanical Properties and Excavation Responses of Basalt with Hidden Cracks at Baihetan Hydropower Station through DFN–FDEM Modeling

by Changdong Ding, Zhenjiang Liu, Xiancheng Mei and Shaoming Ouyang

Appl. Sci. 2024, 14(19), 9069; https://doi.org/10.3390/app14199069 - 8 Oct 2024

Viewed by 1030

Abstract

Basalt is an important geotechnical material for engineering construction in Southwest China. However, it has complicated structural features due to its special origin, particularly the widespread occurrence of hidden cracks. Such discontinuities significantly affect the mechanical properties and engineering stability of basalt, and [...] Read more.

Basalt is an important geotechnical material for engineering construction in Southwest China. However, it has complicated structural features due to its special origin, particularly the widespread occurrence of hidden cracks. Such discontinuities significantly affect the mechanical properties and engineering stability of basalt, and related research is lacking and unsystematic. In this work, taking the underground caverns in the Baihetan Hydropower Station as the engineering background, the size-dependent mechanical behaviors and excavation responses of basalt with hidden cracks were systematically explored based on a synthetic rock mass (SRM) model combining the finite-discrete element method (FDEM) and discrete fracture network (DFN) method. The results showed that: (1) The DFN–FDEM model generated based on the statistical characteristics of the geometric parameters of hidden cracks can consider the real structural characteristics of basalt, whereby the mechanical behaviors found in laboratory tests and at the engineering site could be exactly reproduced. (2) The representative elementary volume (REV) size of basalt blocks containing hidden cracks was 0.5 m, and the mechanical properties obtained at this size were considered equivalent continuum properties. With an increase in the sample dimensions, the mechanical properties reflected in the stress–strain curves changed from elastic–brittle to elastic–plastic or ductile, the strength failure criterion changed from linear to nonlinear, and the failure modes changed from fragmentation failure to local structure-controlled failure and then to splitting failure. (3) The surrounding rock mass near the excavation face of underground caverns typically showed a spalling failure mode, mainly affected by the complex structural characteristics and high in situ stresses, i.e., a tensile fracture mechanism characterized by stress–structure coupling. The research findings not only shed new light on the failure mechanisms and size-dependent mechanical behaviors of hard brittle rocks represented by basalt but also further enrich the basic theory and technical methods for multi-scale analyses in geotechnical engineering, which could provide a reference for the design optimization, construction scheme formulation, and disaster prevention of deep engineering projects. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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27 pages, 2801 KiB

Open AccessArticle

Risk Assessment of TBM Construction Based on a Matter-Element Extension Model with Optimized Weight Distribution

by Tao Fu, Kebin Shi, Renyi Shi, Zhipeng Lu and Jianming Zhang

Appl. Sci. 2024, 14(13), 5911; https://doi.org/10.3390/app14135911 - 6 Jul 2024

Viewed by 802

Abstract

In order to effectively address the potential hazards associated with the construction of Phase II of the YE Water Supply Project’s KS tunnel in Xinjiang, this study employs the WBS-RBS (Work Breakdown Structure and Risk Breakdown Structure) method for risk identification. This approach [...] Read more.

In order to effectively address the potential hazards associated with the construction of Phase II of the YE Water Supply Project’s KS tunnel in Xinjiang, this study employs the WBS-RBS (Work Breakdown Structure and Risk Breakdown Structure) method for risk identification. This approach aims to identify various risks that may arise during TBM (Tunnel Boring Machine) construction. To prevent incomplete risk factor identification resulting from subjective judgment, a risk index system is established based on the identification results. Subsequently, a matter-element extension model is utilized to quantify the risk factors within this index system, and comprehensive weights are determined using variable weight theory to assess construction risk levels. Importance analysis of each index is then conducted to identify those with significant impact on risk evaluation outcomes. Finally, by comparing actual engineering cases with other risk evaluation models, this paper verifies the reliability of its constructed risk assessment model and proposes measures for controlling potential risks based on these evaluations. The paper provides a clear definition of safety risks encountered during TBM construction and conducts comprehensive risk assessments as a valuable reference for research related to the tunnel boring machine construction period in tunnel engineering. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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24 pages, 13754 KiB

Open AccessArticle

Application of Dimension Extending Technique to Unified Hardening Model

by Qian Chen, Hong Zheng and Dongshuai Tian

Appl. Sci. 2024, 14(13), 5677; https://doi.org/10.3390/app14135677 - 28 Jun 2024

Viewed by 708

Abstract

This paper provides the process of incremental constitutive integration for the unified hardening model combined with the transformation stress method. The dimension-extending technique takes the hardening function of the hardening/softening model as the same position as the stress components, so that the constitutive [...] Read more.

This paper provides the process of incremental constitutive integration for the unified hardening model combined with the transformation stress method. The dimension-extending technique takes the hardening function of the hardening/softening model as the same position as the stress components, so that the constitutive integration of the plasticity can be reduced to an initial value problem of differential–complementarity equations, which is solved using the Gauss–Seidel algorithm-based Projection–Correction for the mixed complementarity problem. The Gauss–Seidel based Projection–Correction algorithm does not require the calculation of the Jacobean matrix of the potential function, making it relatively easy to implement in programming. The unified hardening model is proposed based on the modified Cam–Clay model and the sub-loading surface model, and the elastic properties are pressure-dependent. Two processing methods, backward Euler integration and exact elastic property, are used for the variable elasticity properties. The constitutive integration of the increased dimensional unified hardening model is reduced to a special mixed complementarity problem and solved by the proposed algorithm, which does not need to calculate the Jacobean matrix of the potential function, and greatly simplifies the derivation process. Several numerical examples are given to verify the feasibility of the incremental constitutive integration in the unified hardening model, including the single integral point and the boundary value problems. The research results have expanded the scope of use of the Gauss–Seidel based Projection–Correction algorithm. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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16 pages, 9424 KiB

Open AccessArticle

Destabilization Mechanism and Stability Study of Collapsible Loess Canal Slopes in Cold and Arid Regions

by Haozhen Xu, Lingkai Zhang and Chong Shi

Appl. Sci. 2024, 14(11), 4518; https://doi.org/10.3390/app14114518 - 24 May 2024

Cited by 1 | Viewed by 1058

Abstract

The combination of seasonal shutdowns, water conveyance, cold, and drought can easily lead to the deterioration of the anti-seepage system and loess foundation of the canal, which contributes to the destruction of the slope. To reveal the failure mechanism of the collapsible loess [...] Read more.

The combination of seasonal shutdowns, water conveyance, cold, and drought can easily lead to the deterioration of the anti-seepage system and loess foundation of the canal, which contributes to the destruction of the slope. To reveal the failure mechanism of the collapsible loess canal slope, this paper is based on the results of laboratory tests and adopts numerical simulations to analyze the stability of the canal slope under different conditions. The results show that the shear strength indexes and elastic modulus E of loess decrease following an exponential pattern with the increase in wetting-drying and freezing-thawing (WD-FT) cycles. The height of the seepage overflow point yields little effect on the water level behind the impermeable membrane, whereas the height of the water level has a significant effect. In the operation period, the slope under any working conditions is in a relatively stable state. However, the slope with a water level of 4.5 m behind the impermeable membrane tends to be unstable after three WD-FT cycles during the shutdown period. By replacing the surface-degraded loess with sand gravel and picking a depth of 0.9–1.2 m, the slope will maintain a long-term stable state. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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14 pages, 4555 KiB

Open AccessArticle

Three-Dimensional Upper Bound Solution to Estimate Soil Thrust of a Track System on Saturated Clay Slopes under Undrained Conditions

by Sehee Shin and Sang Inn Woo

Appl. Sci. 2024, 14(10), 4335; https://doi.org/10.3390/app14104335 - 20 May 2024

Viewed by 877

Abstract

This study proposes a three-dimensional upper bound solution for estimating the soil thrust of tracked vehicles on saturated clay slopes. The present study considered block, triangular wedge, and trapezoidal wedge failure modes to formulate an upper bound solution for each. The analytical solution [...] Read more.

This study proposes a three-dimensional upper bound solution for estimating the soil thrust of tracked vehicles on saturated clay slopes. The present study considered block, triangular wedge, and trapezoidal wedge failure modes to formulate an upper bound solution for each. The analytical solution for soil thrust was determined as the minimum upper bound solution among those for each failure mode. This analytical solution was validated through numerical simulations that modeled track-ground interactions. Parametric studies, based on the upper bound solution, assessed the impact of track system shape, vehicle weight, undrained shear strength, and ground slope on soil thrust. The analytical solutions and parametric studies provide a rapid method for assessing vehicle operability on clay slopes and offer references for designing tracked vehicles suitable for site conditions. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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23 pages, 6062 KiB

Open AccessArticle

A Novel Identification Approach Using RFECV–Optuna–XGBoost for Assessing Surrounding Rock Grade of Tunnel Boring Machine Based on Tunneling Parameters

by Kebin Shi, Renyi Shi, Tao Fu, Zhipeng Lu and Jianming Zhang

Appl. Sci. 2024, 14(6), 2347; https://doi.org/10.3390/app14062347 - 11 Mar 2024

Cited by 1 | Viewed by 1546

Abstract

In order to solve the problem of the poor adaptability of the TBM digging process to changes in geological conditions, a new TBM digging model is proposed. An ensemble learning prediction model based on XGBoost, combined with Optuna for hyperparameter optimization, enables the [...] Read more.

In order to solve the problem of the poor adaptability of the TBM digging process to changes in geological conditions, a new TBM digging model is proposed. An ensemble learning prediction model based on XGBoost, combined with Optuna for hyperparameter optimization, enables the real-time identification of surrounding rock grades. Firstly, an original dataset was established based on the TBM tunneling parameters under different surrounding rock grades based on the KS tunnel. Subsequently, the RF–RFECV was employed for feature selection and six features were selected as the optimal feature subset according to the importance measure of random forest features and used to construct the XGBoost identification model. Furthermore, the Optuna framework was utilized to optimize the hyperparameters of XGBoost and validated by applying the established TBM dataset of the KS Tunnel. In order to verify the applicability and efficiency of the proposed model in surrounding rock grade identification, the prediction results of five commonly used machine learning models, Optuna–XGBoost, Random Forest (RF), Gradient Boosting Decision Tree (GBDT), Decision Tree (DT), XGBoost, and PSO–XGBoost, were compared and analyzed. The main conclusions are as follows: the feature selection method based on RF–RFECV improved the accuracy by 8.26%. Among the optimal feature subset, T was the most essential feature for the model’s input, while PR was the least important. The Optuna–XGBoost model proposed in this paper had higher accuracy (0.9833), precision (0.9803), recall (0.9813), and F1 score (0.9807) than other models and could be used as an effective means for the lithological identification of surrounding rock grade. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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16 pages, 4338 KiB

Open AccessArticle

The Dynamic Failure Behaviour of High-Pressure Zones during Medium-Scale Ice Indentation Tests

by Ridwan Hossain and Rocky Taylor

Appl. Sci. 2024, 14(2), 849; https://doi.org/10.3390/app14020849 - 19 Jan 2024

Viewed by 805

Abstract

Results from medium-scale ice-crushing dynamic tests are presented in this paper based on a series of indentation experiments on confined ice samples using spherical indenters to simulate high-pressure zones (hpzs) with areas on the order of 10³–10⁴ mm [...] Read more.

Results from medium-scale ice-crushing dynamic tests are presented in this paper based on a series of indentation experiments on confined ice samples using spherical indenters to simulate high-pressure zones (hpzs) with areas on the order of 10³–10⁴ mm². The effects of ice temperature, interaction speed, indenter size and structural compliance on failure behaviour and associated structural dynamics have been studied. Observed failure behaviour consisted of a combination of continuous crushing extrusion and intermittent spalling, both of which were highly dependent on test conditions. Overall, the effects of the studied conditions on ice failure behaviour and associated interaction dynamics were found to be similar to the results reported from previous small-scale experiments, suggesting scale independence of the mechanisms that dominate ice failure behaviour. In general, warmer ice and smaller contact areas are associated with continuous extrusion with intermittent spalling, resulting in smoother peak pressures, while colder ice and larger contact areas tend to result in fracture-dominated behaviour with sharp peaks and substantial load drops. Ice temperature was also found to significantly influence interaction dynamics, with colder ice showing larger amplitude and longer duration dynamic activity, and higher peak pressures. Interaction speed was observed to primarily affect dynamic aspects of ice–structure interactions, with faster tests leading to higher failure frequencies. Similarly, structural compliance was found to mainly impact failure frequency, as well as the extent of load drops, with compliant structures tending to produce more significant load drops following failure. Overall, these experiments have helped enhance our understanding of compressive ice failure and contribute to improved models for dynamic ice–structure interactions. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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18 pages, 7154 KiB

Open AccessArticle

Inversion of Surrounding Red-Bed Soft Rock Mechanical Parameters Based on the PSO-XGBoost Algorithm for Tunnelling Operation

by Yizhe Wu, Huanling Wang and Xinyan Guo

Appl. Sci. 2023, 13(24), 13341; https://doi.org/10.3390/app132413341 - 18 Dec 2023

Cited by 2 | Viewed by 1214

Abstract

In constructing hydraulic tunnels, construction disturbances and complex geological conditions can induce variations in the surrounding rock parameters. To navigate the complex non-linear interplay between rock material parameters and tunnel displacement during construction, this study proposes a hybrid learning model. It employs particle [...] Read more.

In constructing hydraulic tunnels, construction disturbances and complex geological conditions can induce variations in the surrounding rock parameters. To navigate the complex non-linear interplay between rock material parameters and tunnel displacement during construction, this study proposes a hybrid learning model. It employs particle swarm optimization (PSO) to refine the hyperparameters of the eXtreme Gradient Boosting (XGBoost) technique. Sensitivity analysis and inversion of rock parameters is performed by using orthogonal design and the Sobol method to analyze the sensitivity of environmental and rock material factors. The findings indicate that the tunnel depth, elastic modulus, and Poisson ratio are particularly sensitive parameters. Mechanical parameters of the rock mass, identified through sensitivity analysis, are the focal point of this research and are integrated into a three-dimensional computational model. The resulting tunnel displacement calculations serve as datasets for the inversion of the actual engineering project’s surrounding rock mechanical parameters. These inverted parameters were fed into the FLAC3D software (version 7.0), yielding results that align closely with field measurements, which affirms the PSO-XGBoost model’s validity and precision. The insights garnered from this research offer a substantial reference for determining rock mass parameters in tunnel engineering amidst complex conditions. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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17 pages, 4194 KiB

Open AccessArticle

Calculation Method of the Design Thickness of a Frozen Wall with Its Inner Edge Radially Incompletely Unloaded

by Chenchen Hu, Zhijiang Yang, Tao Han and Weihao Yang

Appl. Sci. 2023, 13(23), 12650; https://doi.org/10.3390/app132312650 - 24 Nov 2023

Cited by 2 | Viewed by 837

Abstract

The technology for freezing shaft sinking is widely used for shafts to pass through deep, unstable alluvia with the continuous exploitation of mineral resources. Due to the technique using the sectional excavation and shaft lining construction adopted in deep alluvia, the radial stress [...] Read more.

The technology for freezing shaft sinking is widely used for shafts to pass through deep, unstable alluvia with the continuous exploitation of mineral resources. Due to the technique using the sectional excavation and shaft lining construction adopted in deep alluvia, the radial stress at the inner edge of a frozen wall is incompletely unloaded. In this paper, a mechanical model was established for a frozen wall with its inner edge radially incompletely unloaded. A parameter, α, expressing the degree of being unloaded was introduced, and then a new method of designing and calculating the thickness of the frozen wall was proposed. The range of parameter α was estimated based on the frozen wall–shaft lining interaction forces from field data from a given project. The results indicate that the range of α can be chosen to be from 0.05 to 0.15 in deep alluvia. The design thickness of the frozen wall can be reduced by at least 5% for the frozen wall with the inner edge radially incompletely unloaded. The design thickness is significantly influenced by the strength and elastic modulus of the frozen soil and the elastic modulus of the surrounding unfrozen alluvium. The design and calculation method of frozen wall thickness can provide new ideas for guiding the design of frozen walls in deep alluvia. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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18 pages, 10270 KiB

Open AccessArticle

Simulations of Deformation Failure Process and Refinement of Reinforcement Scheme in the Dabenliu Quarry Slope Using Discontinuous Deformation Analysis

by Wei-Hua Hou, Feng Xiong and Qi-Hua Zhang

Appl. Sci. 2023, 13(19), 11010; https://doi.org/10.3390/app131911010 - 6 Oct 2023

Cited by 1 | Viewed by 1028

Abstract

For this study, the geological engineering features and possible failure modes of the Dabenliu quarry slope in the Jinping-I Hydropower Station were qualitatively analyzed before a method for setting viscous boundary and an algorithm for modeling pre-stressed cables were embedded into a DDA [...] Read more.

For this study, the geological engineering features and possible failure modes of the Dabenliu quarry slope in the Jinping-I Hydropower Station were qualitatively analyzed before a method for setting viscous boundary and an algorithm for modeling pre-stressed cables were embedded into a DDA (Discontinuous Deformation Analysis) computer code to analyze the deformation of the slope under seismic loading. Our simulation results revealed that the middle and upper parts of the slope slipped along the bedding joints (interlayer shear zones) and that the lower part buckled and collapsed after the slope was excavated. This is a typical slipping–buckling failure mode characterized by upper-slipping followed by lower-buckling. Based on the distribution of the simulated internal force of the anchor cables, the reinforcement scheme was adjusted by strengthening the support for the middle and lower parts of the slope, whereas the length and pre-stress of the anchor cables were reduced for the upper part of the slope. The adjusted reinforcement scheme can ensure the stability of the slope under the action of a magnitude 7 earthquake, and the slope may lose stability with no evident collapse under the action of a magnitude 8 earthquake. Finally, the simulation results were verified via a comparison with the monitoring data regarding the slope. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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17 pages, 6733 KiB

Open AccessArticle

Mechanics Model of Floor Heave: Case Study on Thin Coal Seam with Soft Roof and Floor

by Peng Huang, Meng Li, Jing Xie, Guohui Ren, Chengyi Zhao and Francisco Chano Simao

Appl. Sci. 2023, 13(16), 9102; https://doi.org/10.3390/app13169102 - 9 Aug 2023

Cited by 2 | Viewed by 1159

Abstract

The fully mechanized caving roadway’s floor heave has a significant impact on the stability of the narrow coal pillars, the filling body next to the roadway, as well as the entire roadway. Significant floor heave necessitates extensive maintenance and rebuilding work, which has [...] Read more.

The fully mechanized caving roadway’s floor heave has a significant impact on the stability of the narrow coal pillars, the filling body next to the roadway, as well as the entire roadway. Significant floor heave necessitates extensive maintenance and rebuilding work, which has a negative impact on the mine’s regular operations. The costs of sustaining and maintaining the roads are significantly increased by production. In this study, a mechanical model of the floor heave of the road along the goaf is established using the Winker elastic foundation theory model. The mechanical model of the floor heave of the roadway is confirmed when combined with engineering cases. The findings of the study indicate that there is almost no deformation of the side floor of the roadside support and the solid coal. The floor deformation of the roadway area exhibits non-positive symmetry and a “parabolic” characteristic. Roadway width, burial depth, and roadway floor heave all have linearly positive correlations, but elastic modulus of the floor, burial depth, and highway floor heave all have negatively exponential correlations. The maximum deformation of the floor heave, which has a maximum value of 628 mm, is close to the side of the roadway support body; the theoretical model’s maximum value for the floor heave after 100 days of actual deformation monitoring is 645 mm. Between the maximum value and the maximum value as measured, there is a 2.6% error. The paper has important guiding significance for explaining the mechanism of floor heave in goaf roadway and controlling the deformation of the roadway floor. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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16 pages, 8648 KiB

Open AccessArticle

Distribution and Evolution Law of Void Fraction in the Goaf of Longwall Mining in a Coal Mine: Calculation Method and Numerical Simulation Verification

by Jiaqi Wang, Nan Zhou, Chongjing Wang, Meng Li and Guohao Meng

Appl. Sci. 2023, 13(12), 6908; https://doi.org/10.3390/app13126908 - 7 Jun 2023

Viewed by 1267

Abstract

Many voids are produced in the mining process of ore-bearing strata. To explore the development law of voids after mining coal-bearing strata, a theoretical model was established to derive the overall distribution and shape of voids in the goaf. The above theory was [...] Read more.

Many voids are produced in the mining process of ore-bearing strata. To explore the development law of voids after mining coal-bearing strata, a theoretical model was established to derive the overall distribution and shape of voids in the goaf. The above theory was verified using the numerical calculation method. The turning point of the void change was found. The research results show that the void in the goaf was widely distributed around the stope, and the overall void ratio was affected by the mining conditions, such as the mining height and face length. While advancing the working face, the dynamic development of the void first increased and then decreased. At first, the distribution of the void ratio in the goaf was between 0.293 and 0.889 under specific geological conditions, and then, with the advancement of the working face, a large void ratio was reserved at 0~40 m behind the working face. When the working face was advanced to the first roof collapse length, the void fractures continued to decline. Using the above voids, the backfilling of solid mine waste can be effectively realized, and the ecological environment can be protected. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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11 pages, 3301 KiB

Open AccessArticle

Analysis of Sealing Characteristics of Lip Seal Rings for Deep-Sea Separable Pressure Vessels

by Xuepeng Liu, Shiping He and Jianhua Zheng

Appl. Sci. 2023, 13(11), 6843; https://doi.org/10.3390/app13116843 - 5 Jun 2023

Cited by 2 | Viewed by 2601

Abstract

Deep-sea pressure vessels are specialized pressure vessels designed for automatic deployment from underwater to the surface. These vessels find extensive applications in underwater life-saving and transportation. Their interiors are furnished with a pair of sealing rings, one of which is lip-shaped, and the [...] Read more.

Deep-sea pressure vessels are specialized pressure vessels designed for automatic deployment from underwater to the surface. These vessels find extensive applications in underwater life-saving and transportation. Their interiors are furnished with a pair of sealing rings, one of which is lip-shaped, and the other is a convex shape, to ensure a dependable seal. With increasing water depth, the sealing rings experience augmented pressure, resulting in a gradual pressing of the rings into the sealing groove. Using ANSYS workbench finite element software, a two-dimensional axisymmetric lip seal finite element model using forces for overall constraint was established, the complete process of progressive pressing into the sealing groove was simulated, and the deformation, contact stress, maximum shear stress, and von Mises stress distribution was also simulated. We also conducted a comparative analysis of lip seals under low and high-water pressure sealing conditions. The findings of the study indicate that when subjected to a combined effect of the installation pre-tightening force and the working water pressure, the lip seal experiences complete compression into the sealing groove at a specific water depth. When subjected to the simultaneous influence of water pressure on the sealing ring material and friction force on the contact surface, two extremes of contact stress manifest in the primary sealing zone of the lip seal. These extremes have the capacity to elevate the contact stress and the effective sealing width, ultimately leading to an improvement in the sealing performance. Concurrently, as the water pressure gradually increases, the inner concave circle of the sealing ring experiences stretching, leading to a reduction in stress concentration, equivalent stress, and shear stress to a considerable extent. This mechanism ensures that the lip-shaped sealing ring retains sufficient strength. This study offers a viable solution for conducting sealing studies on deep-sea separable pressure vessels. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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24 pages, 9770 KiB

Open AccessArticle

A Three-Dimensional Elastoplastic Constitutive Model for Geomaterials

by Dongshuai Tian and Hong Zheng

Appl. Sci. 2023, 13(9), 5746; https://doi.org/10.3390/app13095746 - 6 May 2023

Cited by 2 | Viewed by 2206

Abstract

The Mohr-Coulomb (M-C) failure criterion has been a popular choice for geotechnical analysis because of its simplicity and ease of use. The fact that the M-C criterion disregards the intermediate principal stress’s impact is a significant drawback. As a result, the M-C criterion [...] Read more.

The Mohr-Coulomb (M-C) failure criterion has been a popular choice for geotechnical analysis because of its simplicity and ease of use. The fact that the M-C criterion disregards the intermediate principal stress’s impact is a significant drawback. As a result, the M-C criterion is only applied to materials under biaxial stress. This paper presents a three-dimensional version of the M-C criterion. The proposed criterion, called the Generalized Mohr-Coulomb (GMC) criterion, considers the intermediate principal stress’s effect, in addition to inheriting the original M-C criterion’s benefits. We obtained the conditions that the strength parameters must satisfy when the GMC criterion fulfills the π plane’s convexity. The GMC criterion can better describe geotechnical materials’ strengths under general stress conditions. Based on an implicit algorithm, the user material subroutine (UMAT) of the three-dimensional GMC model was developed in ABAQUS using the Fortran programming language. The established elastoplastic model’s validity and the program’s accuracy were examined using numerical simulation. Finally, a numerical simulation of a three-dimensional tunnel excavation under various working conditions was performed. The calculation results from the GMC model are precise and have some engineering-related practical significance. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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16 pages, 9846 KiB

Open AccessArticle

The Effect of Block-Matrix Interface of SRM with High Volumetric Block Proportion on Its Uniaxial Compressive Strength

by Guojin Zhu, Yu Ding and Yajun Cao

Appl. Sci. 2023, 13(6), 3463; https://doi.org/10.3390/app13063463 - 8 Mar 2023

Cited by 5 | Viewed by 1643

Abstract

The soil–rock mixture (SRM), as a heterogeneous and discrete geomaterial, can be widely found in nature and may present difficult design and construction issues for structures within or on top of them. Engineers face a difficult problem when determining the mechanical behavior of [...] Read more.

The soil–rock mixture (SRM), as a heterogeneous and discrete geomaterial, can be widely found in nature and may present difficult design and construction issues for structures within or on top of them. Engineers face a difficult problem when determining the mechanical behavior of geomaterials with SRM, especially those with a high volumetric block proportion (VBP). As it is often very difficult to prepare undisturbed and representative samples of these materials. Thus, this paper proposes a novel method that can generate SRM models with a high VBP and produce a block-matrix interface (BMI) around the rock block, which can simulate unwelded SRM in nature. Then, the finite difference method (FDM) is applied to simulate uniaxial compression tests. The conformity of the numerical simulation results with the experimental results shows that the method is reasonable and effective. In addition, the effect of the strength of the BMI, the thickness of the BMI, and the geometrical shape of the rock blocks on the uniaxial compressive strength (UCS) of the SRM are also investigated. The modelling approach proposed in this paper is able to generate BMI in SRMs and enables the effect of the BMI on the SRMs’ properties to be better investigated in numerical simulations. This method can overcome the difficulties of preparing representative and undisturbed experimental cores while saving cost and improving efficiency. Simultaneously, the method proposed in this paper is promising to be extended to three dimensions. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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14 pages, 6324 KiB

Open AccessArticle

Engineering Safety Evaluation of the High Rock Slope of a Hydropower Project: A Case Study of 684 m-High Slope Related to Lianghekou Hydropower Project at Yalong River

by Xiaoyi Xu, Guike Zhang, Wei Huang, Shizhuang Chen, Long Yan and Weiya Xu

Appl. Sci. 2023, 13(3), 1729; https://doi.org/10.3390/app13031729 - 29 Jan 2023

Cited by 2 | Viewed by 1618

Abstract

The stability of the slope is a very important topic in the construction of hydropower projects, especially the slope engineering in the dam area, as its stability will directly affect the safety of engineering. Taking the inlet slope of the flood discharge structure [...] Read more.

The stability of the slope is a very important topic in the construction of hydropower projects, especially the slope engineering in the dam area, as its stability will directly affect the safety of engineering. Taking the inlet slope of the flood discharge structure of Lianghekou Hydropower Project as the research object, based on the analysis and exploration of the geological condition of the slope and the field monitoring data, GA-LSSVM is used to establish the non-linear mapping relationship, and the BP neural network is used to establish the mechanical parameters back analysis of the slope at different water impoundment stages. A numerical simulation model is also established to set up different reservoir impoundments to study the stability and sensibility of the slope and provide guidance for slope operation. This case study shows that there is a hysteresis in the response of slope deformation to reservoir impoundment. At the same time, the mechanical parameters of the slope will be weakened by the seepage. In the process of water level changes, the stability of the slope decreases due to the decrease in mechanical parameters. The study will be practically useful for engineering applications. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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19 pages, 9536 KiB

Open AccessArticle

A Design Method and Application of Backfilling Hydraulic Supports in Reforming Top-Coal Caving Hydraulic Supports

by Qiang Zhang, Peitao Shi, Meng Li, Tingcheng Zong and Weijian Song

Appl. Sci. 2023, 13(2), 987; https://doi.org/10.3390/app13020987 - 11 Jan 2023

Cited by 2 | Viewed by 1632

Abstract

Solid backfilling is an environmentally friendly method of coal mining. Backfilling hydraulic supports are important devices in solid backfill mining. In order to speed up the design and manufacturing process of them, this paper proposes a method of hydraulic support reformation and evaluation. [...] Read more.

Solid backfilling is an environmentally friendly method of coal mining. Backfilling hydraulic supports are important devices in solid backfill mining. In order to speed up the design and manufacturing process of them, this paper proposes a method of hydraulic support reformation and evaluation. The mechanical models of top-coal caving hydraulic support and backfilling hydraulic support were established to analyze the stress characteristics of the main structure. ABAQUS was used to establish the 3D numerical model to analyze the load-bearing characteristics, as well as verify the strength requirement. In addition, the structural characteristics, compaction characteristics, geological adaptation characteristics, and interference characteristics of the structure were analyzed using motion simulation. After reforming, the ramming force is just above 2.0 MPa, and the utilization ratio of the old parts of the top-coal caving hydraulic support is more than 50%, which saved the costs of the new backfilling hydraulic support and reduced the waste of idle top-coal caving hydraulic support. The successful application of the backfilling hydraulic support in the Tangshan mine showed the rationality of the reform design. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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13 pages, 5288 KiB

Open AccessArticle

Investigation on Deformation Behavior of the Crossing Section of Two Municipal Road Tunnels during Construction

by Chen-Yu Zhao, Ren-Hui Yue, Yu-Liang Lin, Cong-Jun Huang and Xu Jiang

Appl. Sci. 2022, 12(23), 12274; https://doi.org/10.3390/app122312274 - 30 Nov 2022

Cited by 2 | Viewed by 1477

Abstract

With the development of urbanization, the transportation network of underground tunnels has been gradually formed and improved. It is a complicated issue for engineering construction when two municipal road tunnels intersect at one point. Based on a construction site of the crossing point [...] Read more.

With the development of urbanization, the transportation network of underground tunnels has been gradually formed and improved. It is a complicated issue for engineering construction when two municipal road tunnels intersect at one point. Based on a construction site of the crossing point of the Huayuan Road Tunnel and Luzhou Road Tunnel in Hefei City, China, the finite element analysis method is used to calculate and analyze the deformation characteristics of the crossing point of the tunnels during the asymmetric construction of connecting parts. The deformation behaviors of the crossing point of tunnels subjected to symmetrical construction are also studied for comparison. Results show that the deformations of the supporting pile and tunnel frame structures increase rapidly when they are subjected to asymmetric construction, while the lateral movement of the supporting pile and the deformation of the tunnel structure can be greatly limited when the symmetrical construction method is adopted. Some suggestions for engineering construction are put forward to ensure the safety of the structure, such as multi-stage construction and temporary supporting measure. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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17 pages, 2037 KiB

Open AccessArticle

Experimental Investigation and Micromechanics-Based Analytical Modeling of Creep and Relaxation Behaviors of Beishan Granite

by Qiaojuan Yu, Qizhi Zhu, Yunxing Lu and Zhanyou Luo

Appl. Sci. 2022, 12(23), 12083; https://doi.org/10.3390/app122312083 - 25 Nov 2022

Cited by 1 | Viewed by 1231

Abstract

This paper investigates experimentally and numerically the short- and long-term strength and deformation behaviors of Beishan granite at room temperature. Single-stage creep, relaxation, and conventional triaxial compression tests were performed on cylindrical rock samples. Its typical brittle response is captured and the dependence [...] Read more.

This paper investigates experimentally and numerically the short- and long-term strength and deformation behaviors of Beishan granite at room temperature. Single-stage creep, relaxation, and conventional triaxial compression tests were performed on cylindrical rock samples. Its typical brittle response is captured and the dependence of peak strength on confining pressure and time-dependent response on deviatoric stress are revealed. For constitutive modeling, a unified micromechanics-based plasticity-damage model is formulated based on the Mori–Tanaka method and the subcritical cracking theory postulate, with the focus on simulating both instantaneous strain and time-dependent deformation process over a broad range of time scales. Its unification is achieved by representing the evolution of damage, which is strongly coupled with plastic deformation induced by frictional sliding along closed cracks, as an internal variable that can be decomposed into instantaneous and time-dependent parts. The performance of the model with analytical predictions is well validated using the experimental results on Beishan granite. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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12 pages, 1913 KiB

Open AccessBrief Report

Simulation Method and Application of Three-Dimensional DFN for Rock Mass Based on Monte-Carlo Technique

by Ang Li, Yaodong Li, Feng Wu, Guojian Shao and Yang Sun

Appl. Sci. 2022, 12(22), 11385; https://doi.org/10.3390/app122211385 - 10 Nov 2022

Cited by 1 | Viewed by 1576

Abstract

In this study, the authors simulate a polygonal discrete fracture network (DFN) in rock masses. The probability models of the relevant geological parameters, including the orientation, trace length, volume density, and coordinates of the centroid, are firstly developed as fractures are in the [...] Read more.

In this study, the authors simulate a polygonal discrete fracture network (DFN) in rock masses. The probability models of the relevant geological parameters, including the orientation, trace length, volume density, and coordinates of the centroid, are firstly developed as fractures are in the shape of rectangles. In the process, the probability distribution of rectangular fractures with side lengths as random variables is introduced and described in terms of mean trace lengths on the basis of the probability model of disk-shaped fracture with the diameter as the random variable. The relationship between the volume density and the linear density of rectangular fractures is given for a negative exponential distribution. Following this, the coordinates of the vertices of fractures are derived based on spatial algebraic geometry, and the data for the three-dimensional DFN model are generated using the Monte-Carlo technique. The resulting three-dimensional DFN is visualized by calling the Open GL graphics database in the environment of Visual C, and the process of implementation of the DFN simulation is given. Finally, the validity of the simulation is verified by applying it to engineering practice. Full article

(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)

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