Geomechanics for Energy and the Environment最新文献_第7页

Comparative experimental study on thermo-mechanical responses of phase-change and normal energy piles 相变桩与普通能量桩热-力响应对比试验研究

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-10-20 DOI: 10.1016/j.gete.2025.100758

Jiaxin Liu, Chaoran Wang, Kehao Chen, Yang Shen, Chanjuan Han

Phase change energy piles (PCEP) have garnered attention from researchers in light of their higher equivalent specific heat and enhanced heat exchange potential compared to normal energy piles (NEP), making them effective for optimizing energy pile efficiency. However, research on the thermo-mechanical response of PCEP across different operational modes, environmental conditions, and multi-physical fields, particularly experimental studies, remains limited. Apart from this, few studies have clarified whether phase change occurs during both winter mode and summer mode. The determination of the phase state significantly affects the thermal efficiency. This study investigates the thermal and mechanical performance of PCEP and NEP through laboratory testing, comprehensively examining the effects of microencapsulated phase change material (microPCM) incorporation and variation in operational parameters. To address the low reliability of conventional PCMs, the microPCM with a unique shell structure was employed in the fabrication of PCEP. Key findings reveal that PCEP enhances heat energy harvesting under both winter and summer modes and promotes temperature recovery during cooling. Both pile types exhibit similar trends in normalized soil temperature change and pile heat reaction force. Moreover, PCEP experiences a slight increase in pile top force reduction during cooling, due to the higher thermal expansion coefficient of phase change concrete. The study confirms that PCEP offers a promising approach for optimizing energy efficiency and enhancing thermal management in geotechnical applications.

相对于普通能源桩（NEP），相变能源桩（PCEP）具有更高的等效比热和更强的热交换势，是优化能源桩效率的有效手段，因此受到了研究人员的关注。然而，关于PCEP在不同工作模式、环境条件和多物理场中的热-力学响应的研究，特别是实验研究仍然有限。除此之外，很少有研究澄清相变是否同时发生在冬季模态和夏季模态。相态的确定对热效率有重要影响。本研究通过实验室测试研究了PCEP和NEP的热力学性能，全面考察了微封装相变材料（microPCM）掺入和操作参数变化对PCEP和NEP的影响。为解决传统pcm可靠性低的问题，采用具有独特壳体结构的微pcm制造PCEP。主要研究结果表明，在冬季和夏季模式下，PCEP都能增强热能收集，并促进冷却过程中的温度恢复。两种桩型的归一化土温变化和桩热反力变化趋势相似。此外，由于相变混凝土的热膨胀系数较高，PCEP在冷却过程中桩顶减力略有增加。该研究证实，PCEP为优化能源效率和加强岩土工程应用中的热管理提供了一种很有前途的方法。

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引用次数: 0

Sealing simulation experiment of old well collapse debris in carbon capture and storage (CCS) 碳捕集与封存中老井坍塌碎屑密封模拟实验

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-12-04 DOI: 10.1016/j.gete.2025.100776

Yuda Zhang , Jingnan Dong , Guangjie Yuan , Yan Xia , Hong Zhang , Pan Fu

Carbon storage in depleted reservoirs has emerged as a critical technology for mitigating atmospheric CO₂ concentrations, where the sealing integrity of old wells constitutes a pivotal factor in site selection. This study investigates the sealing performance of old wells containing fish and buried by wellbore collapse debris through comprehensive experimental approaches, including full-scale wellbore debris sealing simulations and small-scale core permeability tests. The experimental design systematically examined key variables including debris composition, compaction degree, and permeability characteristics under varying hydraulic pressures. Results demonstrate two distinct failure mechanisms: (1) gas breakthrough occurring at pressure differentials of 1.3–2.7 MPa with approximately 30-second response time, where gas migration predominantly follows interfacial pathways between compacted debris (permeability <0.031 D) and casing/fish structures; and (2) persistent gas leakage through debris pore networks, exhibiting permeability ranges of 0.0024–0.031 D. These findings provide fundamental insights into failure dynamics of debris-sealed abandoned wells, offering critical empirical data for safety assessment of CCS/CCUS reservoir candidates. The experimental methodology establishes a replicable framework for evaluating wellbore sealing integrity under simulated reservoir conditions.

枯竭储层中的碳储存已成为降低大气CO₂浓度的关键技术，其中老井的密封完整性是选址的关键因素。本研究通过全面的实验方法，包括全尺寸井筒碎屑密封模拟和小规模岩心渗透率测试，研究了含鱼井和井筒坍塌碎屑埋藏的老井的密封性能。试验设计系统地检查了不同水压下的关键变量，包括碎屑成分、压实程度和渗透性特征。结果显示了两种不同的破坏机制：(1)气侵发生在压力差为1.3-2.7 MPa时，响应时间约为30秒，气体运移主要沿着压实碎屑（渗透率<；0.031 D）与套管/鱼体结构之间的界面通道进行；(2)碎屑孔隙网络中持续的气体泄漏，渗透率范围为0.0024 ~ 0.031 d。这些发现为碎屑密封废弃井的破坏动力学提供了基本见解，为CCS/CCUS候选储层的安全性评估提供了关键的经验数据。该实验方法建立了一个可复制的框架，用于在模拟油藏条件下评估井筒密封完整性。

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引用次数: 0

Mechanism of anomalous “internal subsidence and peripheral uplift” in a salt mine goaf: A multi-source validated superposition of poroelastic uplift and mining-induced subsidence 盐矿采空区异常“内沉降外隆升”机理：多源验证的孔弹性隆升与采动沉陷叠加

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-11-19 DOI: 10.1016/j.gete.2025.100769

Ahu Zhao , Yinping Li , Xilin Shi , Shefeng Hao , Zengguang Che , Kun Yang , Mingnan Xu , Hongling Ma

Solution mining in salt mine typically induces regional ground subsidence and even localized collapse. However, monitoring data from a large-scale salt mine in eastern China reveal significant ground uplift in peripheral areas, while persistent subsidence occurs in the Internal mining area. This study systematically investigates the mechanisms underlying this anomalous phenomenon through integrated InSAR and first-order leveling surveys, detailed geological exploration, and theoretical modeling approaches. A six-year deformation monitoring campaign identified anomalous surface deformation characterized by internal subsidence and peripheral uplift, exhibiting pronounced spatial heterogeneity and temporal non-stationarity. Field core drilling, hydraulic connectivity testing, borehole inflow monitoring, and dynamic injection-extraction analyses confirmed that the high-pressure aquifer within the Dainan Formation(Ed) is an anthropogenic geological formation resulting from injection-extraction imbalance. The core hypothesis posited in this study is that leakage from injection wells elevates pore pressure in deep sandstone aquifers, triggering poroelastic expansion effects that fundamentally drive the sustained ground uplift around mined-out regions. To quantitatively evaluate this large-scale uplift deformation, the issue was conceptualized as a semi-infinite spatial boundary condition, and a corresponding computational model for surface uplift was developed. Following numerical validation of the model and integration with established subsidence theories associated with solution mining, the spatiotemporal deformation patterns from 2018 to 2023 were successfully inverted. The results indicate that the observed deformation pattern of internal subsidence and peripheral uplift arises from the spatial superposition of ground subsidence induced by salt mining and poroelastic uplift driven by injection-induced leakage. The established model quantitatively assesses the contributions of critical injection-extraction parameters to ground deformation, providing a universally applicable theoretical framework for predicting future surface deformation and facilitating geological hazard mitigation.

盐矿溶液开采通常会引起区域地面沉陷甚至局部塌陷。然而，中国东部某大型盐矿的监测数据显示，周边地区地面明显隆起，而内部矿区则持续下沉。本研究通过综合InSAR和一级水准测量，详细的地质勘探和理论建模方法，系统地探讨了这种异常现象的机制。一项为期6年的变形监测活动确定了以内部沉降和外围隆起为特征的异常地表变形，表现出明显的空间异质性和时间非平稳性。现场岩心钻探、水力连通性测试、井眼流入监测和动态注采分析证实，戴南组高压含水层是由注采不平衡引起的人为地质层。本研究提出的核心假设是，注水井的泄漏提高了深部砂岩含水层的孔隙压力，引发了孔隙弹性膨胀效应，从根本上推动了采空区周围地面的持续隆升。为了定量评价这种大规模的隆升变形，将该问题概念化为半无限空间边界条件，并建立了相应的地表隆升计算模型。在对模型进行数值验证的基础上，结合已有的沉降理论，成功反演了2018 - 2023年的时空变形格局。结果表明，观测到的内部沉降和周边隆升的变形模式是由采盐引起的地面沉降和注泄引起的孔弹性隆升在空间上叠加而成的。建立的模型定量评价了注采关键参数对地面变形的贡献，为预测未来地表变形和促进地质灾害减灾提供了普遍适用的理论框架。

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引用次数: 0

Discrimination of critically stressed faults and safety-optimized hydraulic fracturing design: Insights from meter-scale physical modeling 临界应力断层的识别和安全优化水力压裂设计：来自米尺度物理建模的见解

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-09-23 DOI: 10.1016/j.gete.2025.100748

Xiaodong Wang , Qianting Hu , Baocai Wang , Chunhui Cheng , Yongjiang Luo

This study presents an integrated approach combining metre-scale physical experiments, numerical simulations and theoretical modelling to systematically investigate the mechanisms and controlling factors of fault slip induced by hydraulic fracturing, with the ultimate goal of establishing fundamental design principles for fault slip mitigation. First, we quantify the influence of fault geometry and mechanical properties on stress concentration by deriving a quantitative stress concentration equation through multivariate regression analysis. Second, a novel three-dimensional (3D) Coulomb failure stress (CFS) expression incorporating stress concentration coefficients is proposed to overcome the limitations of conventional regional stress analysis. Third, the theoretical stress transfer model is validated against experimental data, showing strong agreement between predicted and measured CFS changes, with a relative error of less than 10 %. Our results demonstrate that hydraulically isolated faults are primarily controlled by regional stress states during slip initiation. Critically stressed faults exhibit significant slip near injection points, while non-critical faults remain stable. The proposed 3D CFS expression successfully discriminates between stress-transfer induced PNR-1z and pore-pressure driven PNR-2 seismic events. Finally, faults are classified into four distinct types, each associated with tailored hydraulic fracturing design protocols: type I faults require mandatory avoidance; type II-III faults require controlled injection parameters; and type IV faults permit cost-optimised operations. These findings provide theoretical advances and practical guidelines for mitigating induced seismicity in hydraulic fracturing.

本研究采用米尺度物理实验、数值模拟和理论建模相结合的综合方法，系统研究水力压裂诱发断层滑动的机理和控制因素，最终建立断层滑动缓解的基本设计原则。首先，通过多元回归分析，推导出定量应力集中方程，量化断层几何形状和力学性质对应力集中的影响。其次，针对传统区域应力分析的局限性，提出了一种包含应力集中系数的三维库仑破坏应力（CFS）表达式。第三，将理论应力传递模型与实验数据进行对比验证，结果表明，CFS变化预测值与实测值吻合较好，相对误差小于10 %。研究结果表明，水力隔离断层主要受起滑过程中区域应力状态的控制。临界应力断层在注入点附近表现出明显的滑移，而非临界断层则保持稳定。提出的三维CFS表达式成功区分了应力传递诱发的PNR-1z和孔隙压力驱动的PNR-2地震事件。最后，将断层分为四种不同的类型，每种类型都与定制的水力压裂设计方案相关：I型断层需要强制规避；II-III型故障需要控制注入参数；IV型故障可以实现成本优化操作。这些发现为减轻水力压裂诱发地震活动提供了理论进展和实践指导。

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引用次数: 0

Impact of surface roughness on the mechanical behaviour of rock discontinuities 表面粗糙度对岩石不连续面力学行为的影响

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-10-13 DOI: 10.1016/j.gete.2025.100757

Camilo Casagrande , Teresa Maria Pique , Diego Manzanal , Martín Sánchez

Geological storage of carbon dioxide (

C O_{2}

) is a key method for modern decarbonization, yet predicting the gas migration through the reservoir remains a geomechanical challenge. A major uncertainty stems from the potential reactivation of pre-existing rock discontinuities, whose shear strength is strongly influenced by surface roughness. In this work, we quantify the influence of roughness on discontinuity shear behaviour through triaxial direct shear tests. Three representative discontinuity geometries were prepared, their surface morphologies quantified with standard roughness parameters, and then loaded under normal stresses ranging from 0.7 MPa to 7 MPa. We compare three shear criteria and three ways to measure roughness to contrast the experimental results, assessing their suitability for predicting the shear strength of rock discontinuities. We found good agreement between roughness parameters and experimental shear strength for surfaces with greater waviness, whereas asperity-dominated discontinuities are systematically underpredicted. Additionally, greater normal displacement was observed where steep asperities were present, which is consistent with enhanced interlocking. Results are consistent across materials, indicating that surface morphology outweighs bulk strength. This analysis aims to improve the accuracy of shear strength predictions, which is essential for understanding subsurface behaviour in geological

C O_{2}

storage.

二氧化碳的地质储存是现代脱碳的关键方法，但预测天然气在储层中的运移仍然是一个地质力学挑战。一个主要的不确定性来自于先前存在的岩石不连续面的潜在重新激活，其抗剪强度受到表面粗糙度的强烈影响。在这项工作中，我们通过三轴直剪试验量化粗糙度对不连续剪切行为的影响。制备了三种具有代表性的不连续几何形状，用标准粗糙度参数量化其表面形貌，然后在0.7 MPa至7 MPa的法向应力范围内加载。我们比较了三种剪切准则和三种测量粗糙度的方法，以对比实验结果，评估它们在预测岩石不连续面抗剪强度方面的适用性。我们发现粗糙度参数和实验抗剪强度之间有很好的一致性，而粗糙度主导的不连续面被系统地低估了。此外，在陡坡处观察到更大的正常位移，这与增强的联锁相一致。结果是一致的材料，表明表面形态超过体积强度。该分析旨在提高抗剪强度预测的准确性，这对于了解地质CO2储存的地下行为至关重要。

{"title":"Impact of surface roughness on the mechanical behaviour of rock discontinuities","authors":"Camilo Casagrande , Teresa Maria Pique , Diego Manzanal , Martín Sánchez","doi":"10.1016/j.gete.2025.100757","DOIUrl":"10.1016/j.gete.2025.100757","url":null,"abstract":"<div><div>Geological storage of carbon dioxide (<span><math><mrow><mi>C</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>) is a key method for modern decarbonization, yet predicting the gas migration through the reservoir remains a geomechanical challenge. A major uncertainty stems from the potential reactivation of pre-existing rock discontinuities, whose shear strength is strongly influenced by surface roughness. In this work, we quantify the influence of roughness on discontinuity shear behaviour through triaxial direct shear tests. Three representative discontinuity geometries were prepared, their surface morphologies quantified with standard roughness parameters, and then loaded under normal stresses ranging from 0.7 MPa to 7 MPa. We compare three shear criteria and three ways to measure roughness to contrast the experimental results, assessing their suitability for predicting the shear strength of rock discontinuities. We found good agreement between roughness parameters and experimental shear strength for surfaces with greater waviness, whereas asperity-dominated discontinuities are systematically underpredicted. Additionally, greater normal displacement was observed where steep asperities were present, which is consistent with enhanced interlocking. Results are consistent across materials, indicating that surface morphology outweighs bulk strength. This analysis aims to improve the accuracy of shear strength predictions, which is essential for understanding subsurface behaviour in geological <span><math><mrow><mi>C</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> storage.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"44 ","pages":"Article 100757"},"PeriodicalIF":3.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental investigation of damage behavior of coal pillars during injection-production in abandoned coal mine gas storage 废弃煤矿储气库注采过程中煤柱破坏行为试验研究

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-11-06 DOI: 10.1016/j.gete.2025.100766

Xiaoming Shi , Lei Geng , Xuejie Deng , Gustavo Paneiro , Zhide Wu , Yang Li , Hao Liu , Jianye Feng

The mechanical behavior and damage evolution of coal pillars under cyclic loading govern the long-term stability of underground gas storage in abandoned coal mines. Using coal from Ningxia, we conducted uniaxial constant-amplitude cyclic tests and incremental loading-unloading tests, combined with acoustic-emission monitoring, damage-mechanics modeling, and PFC particle-flow simulations, to elucidate a stress-threshold-controlled evolution law. The results show that the first loading cycle dominates damage progression, contributing 36.75 %-75.19 % of the cumulative AE ringing counts and markedly degrading mechanical integrity. Also, macroscopic failure is mainly shear (73.9 %-80.1 %), while the proportion of tensile events rises with stress amplitude. This study also shows that a stress-threshold range of about 89.2 %-95.4 % UCS is identified for the coal specimens, within which sub-threshold damage is self-limiting and the damage variable grows by only 9.3 % after 50 cycles, whereas super-threshold loading induces a three-stage process of compaction, stable accumulation, and accelerated instability. Finally, a damage-evolution model that couples Ashby’s microcrack mechanics with geometric damage predicts a nonlinear link between crack growth and loss of load-bearing capacity and reproduces the measured stress-damage trajectory more accurately than classical formulas. PFC simulations further show that a stress difference of 0.05 MPa can trigger an abrupt transition to instability, confirming the decisive control of the threshold. These findings provide a basis for safety-threshold design and long-term stability assessment of rock masses under cyclic loading.

循环荷载作用下煤柱的力学行为和损伤演化决定着废弃煤矿地下储气库的长期稳定性。利用宁夏产煤进行单轴等幅循环试验和增量加卸载试验，结合声发射监测、损伤力学建模和PFC颗粒流模拟，阐明了应力阈值控制的演化规律。结果表明，第一次加载周期对损伤进程起主导作用，对累积声发射振铃数的贡献为36.75 % ~ 75.19 %，并显著降低了机械完整性。宏观破坏以剪切破坏为主（73.9 % ~ 80.1 %），拉伸破坏的比例随应力幅值的增大而增大。研究还表明，煤样的应力阈值范围约为89.2 % ~ 95.4 % UCS，在此范围内，亚阈值损伤是自限的，50次循环后损伤变量仅增长9.3 %，而超阈值加载则导致压实、稳定堆积和加速失稳三个阶段的过程。最后，将Ashby微裂纹力学与几何损伤相结合的损伤演化模型预测了裂纹扩展与承载能力损失之间的非线性联系，并比经典公式更准确地再现了测量的应力-损伤轨迹。PFC模拟进一步表明，0.05 MPa的应力差可以触发突变到不稳定，证实了阈值的决定性控制。研究结果为循环荷载作用下岩体的安全阈值设计和长期稳定性评价提供了依据。

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引用次数: 0

Numerical study on enhancing coalbed methane recovery using stress relief by multiple cavities 多空腔应力释放提高煤层气采收率的数值研究

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-09-15 DOI: 10.1016/j.gete.2025.100742

Yi Chen, Lei Zhou, Liulin Fang, Yu Peng, Xiaocheng Li

Conventional horizontal well direct fracturing technology is inadequate for deep coalbed methane (DCBM) surface extraction. The extraction of DCBM presents a technical obstacle that impedes the advancement of China's CBM industry. This study explores the potential of a novel approach involving horizontal wells with multi-cavities to enhance DCBM extraction. A three-dimensional numerical tool, based on the elastic-plastic damage model and material point method (MPM), was developed to examine permeability enhancement and CBM desorption induced by cavities. Systematic engineering simulations were conducted to validate the effectiveness of DCBM extraction. The findings are as follows: 1) The three-dimensional numerical tool accurately simulates large deformation, large displacement, and inner boundary self-contact issues during cavity-induced collapse in deep coal. 2) A single cavity contributes an effective stress-relief volume 23.95 times greater than the cavity volume; permeability increases by 5–800 times in the plastic zones and by 1–5 times in the elastic zones over the initial permeability, and a total CBM desorption of 197.22 m³ is achieved. 3) The DCBM production volume enhanced by horizontal wells with multi-cavities is 24.98 times greater than hydraulic fracturing, with an average production exceeding 10,000 m³ /d and remaining above 6000 m³ /d after one year of extraction. 4) Optimal performance of horizontal wells with multi-cavities can be achieved by reducing the cavity angle and spacing while increasing the cavity width and length. Based on these results, implementing compound fracturing in horizontal wells with multi-cavities is recommended. This study provides a numerical tool and new insights for enhancing DCBM extraction.

常规水平井直接压裂技术在深部煤层气地面开采中存在一定的不足。DCBM的开采是制约中国煤层气产业发展的技术障碍。本研究探索了一种涉及多空腔水平井的新方法的潜力，以提高DCBM的提取。基于弹塑性损伤模型和材料点法（MPM），建立了三维数值工具，研究了空腔对煤层气的增渗和解吸作用。通过系统工程仿真验证了DCBM提取的有效性。研究结果表明：1)三维数值工具准确模拟了深部煤层空腔塌陷过程中的大变形、大位移和内边界自接触问题。2)单个空腔对有效应力消除体积的贡献是空腔体积的23.95倍；与初始渗透率相比，塑性区渗透率增加5 ~ 800倍，弹性区渗透率增加1 ~ 5倍，煤层气总解吸量为197.22 m³ 。3)多腔水平井提高DCBM产量是水力压裂的24.98倍，平均产量超过10000 m³ /d，开采1年后仍保持在6000 m³ /d以上。4)通过减小空腔角度和间距，增大空腔宽度和长度，实现多空腔水平井的最佳性能。在此基础上，建议在多空腔水平井中实施复合压裂。该研究为加强DCBM提取提供了数值工具和新的见解。

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引用次数: 0

Load transfer analysis of driven energy pile under combined thermal and mechanical loading 热-力复合荷载作用下动力桩的荷载传递分析

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-09-25 DOI: 10.1016/j.gete.2025.100751

Changyi Yang , Jingpei Li , Guiwei Tian , Chang Liu , Ning Lai

This study presents a semi-analytical analysis on load transfer mechanisms of driven energy piles in clay, with a comprehensive consideration of installation effects, reconsolidation of surrounding soils and combined thermal and mechanical loading. The installation effects of driven energy piles are modelled based on the cavity expansion theory. Analytical expressions for thermally induced displacements, including axial and radial expansion of pile, are derived. A hysteresis hyperbolic load transfer function is proposed according to the Masing’s criterion to incorporate the loading and unloading induced by temperature changes. Through numerical simulations and experimental validations, the axial strain and stress distribution within the pile under varying conditions is explored, where good agreements between the proposed theoretical method, numerical results and field tests are observed. A thorough comparison is conducted between driven energy piles and bored energy piles to assess the impact of installation effects on pile-soil relative displacement, shaft friction, and the ultimate bearing capacity. It is found that although the bearing capacity of driven energy piles is greater than that of bored energy piles, the axial stress within driven energy piles is also higher under thermal load. The findings shed light on the design and optimization of PHC energy piles in geothermal systems.

综合考虑安装效应、周围土体的再固结和热力复合荷载，对粘土中动力桩的荷载传递机理进行了半解析分析。基于空腔膨胀理论，对动力桩的安装效果进行了模拟。导出了热致位移的解析表达式，包括桩的轴向和径向扩展。根据Masing准则，提出了一个包含温度变化引起的加载和卸载的滞后双曲荷载传递函数。通过数值模拟和试验验证，探讨了不同工况下桩内的轴向应变和应力分布，理论方法、数值结果和现场试验结果吻合较好。对动力桩和钻孔动力桩进行了全面对比，评估了安装效应对桩土相对位移、桩身摩擦和极限承载力的影响。研究发现，虽然打入能源桩的承载力大于钻孔能源桩，但在热荷载作用下，打入能源桩内部的轴向应力也更高。研究结果为地热系统中PHC能源桩的设计与优化提供了参考。

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引用次数: 0

A new mechanism on how LCMs deposited stably to bridge during wellbore strengthening and its analytical model 井眼加固过程中lcm稳定沉积的新机制及其分析模型

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-10-10 DOI: 10.1016/j.gete.2025.100756

Lisong Zhang , Kai Du , Wang Chen

LCMs (lost circulation materials) deposited stably to bridge (abbreviated as LCMs – DSTB) is the most critical step during the wellbore strengthening. However, it has not been fully understood on how LCMs deposited stably to bridge within the fracture. In view of this, a new mechanism was proposed to illustrate LCMs – DSTB, from two aspects of LCMs deposited compressively stably to bridge and LCMs deposited geometrically stably to bridge. Then, the analytical model was respectively established for LCMs – DSTB from two aspects, and three parameters were proposed to demonstrate LCMs – DSTB, namely, the coefficient of LCMs – DSTB, the location of LCMs – DSTB, and the time of LCMs – DSTB. Especially, to establish the analytical model, the fracture–related parameters were investigated such as the fracture width, the fracture length and the fracture pressure. The analytical model was validated by the numerical model, by comparisons of the coefficient of LCMs – DSTB, the location of LCMs – DSTB, and the time of LCMs – DSTB, as well as the fracture–related parameters, with the maximum deviation of less than 5.38 %. Finally, the effects of the loss rate, formation permeability, time difference, equivalent diameter on LCMs – DSTB were discussed. The results showed that: (1) the smaller loss rate, the shorter time difference and the larger formation permeability are beneficial for LCMs – DSTB; (2) the reasonable equivalent diameter of 0.4 was recommended for LCMs – DSTB.

lcm（漏失材料）稳定沉积到桥上（简称lcm - DSTB）是井筒加固过程中最关键的步骤。然而，对于lcm如何稳定沉积并在裂缝内桥接还没有完全了解。鉴于此，本文提出了一种新的lcm - DSTB机理，从lcm压缩稳定沉积到桥和lcm几何稳定沉积到桥两个方面来解释lcm - DSTB。然后，从两个方面分别建立了lcm - DSTB的解析模型，并提出了lcm - DSTB的系数、lcm - DSTB的位置和lcm - DSTB的时间三个参数来论证lcm - DSTB。为了建立分析模型，研究了裂缝宽度、裂缝长度和裂缝压力等与裂缝相关的参数。通过数值模型、lcm - DSTB系数、lcm - DSTB位置、lcm - DSTB时间以及裂缝相关参数的比较，验证了解析模型的正确性，最大偏差小于5.38 %。最后讨论了损失率、地层渗透率、时差、当量直径等因素对lcm - DSTB的影响。结果表明：(1)更小的损失率、更短的时差和更大的地层渗透率有利于lcm - DSTB；(2) LCMs - DSTB的合理等效直径为0.4。

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引用次数: 0

Fracture evolution and energy dissipation characteristics of limestone under triaxial loading and unloading experiments 三轴加卸载试验下灰岩断裂演化及能量耗散特征

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment

Pub Date : 2025-12-01 Epub Date: 2025-11-17 DOI: 10.1016/j.gete.2025.100771

Ding Liu , Bowen Cheng , Xinping Li , Mingyang Wang , Yu Wang , Yuliang Zhang

To elucidate the failure mechanism of limestone during excavation-induced unloading in underground engineering, a series of triaxial loading–unloading tests were conducted under various confining pressures(σ₃) and initial unloading levels (n). The results show that increasing σ₃ enhances both the peak strength and plastic deformation capacity of limestone. Although a higher n leads to a strength increase, it remains lower than that under conventional triaxial loading and intensifies the brittleness of failure. In terms of energy evolution, both the maximum elastic strain energy (U_e-max) and the maximum dissipated energy (U_d_-max) increase linearly with σ₃. During the unloading path, the dissipated energy exhibits a pronounced hysteresis effect, which becomes more evident at higher n values, revealing the sudden energy release characteristic of highly pre-damaged rock masses. Macro- and micro-scale analyses indicate that the failure mode evolves from tensile–shear mixed failure to shear-dominated failure as σ₃ and n increase. Furthermore, the unloading damage constitutive model, established based on strain equivalence and Weibull distribution, shows good agreement with experimental results, effectively characterizes the damage evolution process of limestone.

为了阐明地下工程开挖卸荷过程中石灰岩的破坏机理，在不同围压（σ₃）和初始卸荷水平(n)下进行了一系列三轴加卸载试验。结果表明，σ 3的增加可以提高石灰石的峰值强度和塑性变形能力。较高的n值虽然提高了强度，但仍低于常规三轴载荷下的强度，并加剧了破坏的脆性。在能量演化方面，最大弹性应变能（Ue-max）和最大耗散能（Ud-max）都随着σ₃的增加而线性增加。在卸荷过程中，耗散能量表现出明显的滞后效应，且在n值越高时更为明显，揭示了高度预损伤岩体能量释放的突变性。宏观和微观尺度分析表明，随着σ₃和n的增大，破坏模式由拉剪混合破坏向剪切为主破坏演化。基于应变等效和威布尔分布建立的卸荷损伤本构模型与试验结果吻合较好，有效表征了灰岩的损伤演化过程。

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