Hasil untuk "Engineering geology. Rock mechanics. Soil mechanics. Underground construction"

Shucai Li, Bin Liu, Lei Chen et al.

Geological prospecting and the identification of adverse geological features are essential in tunnel construction, providing critical information to ensure safety and guide engineering decisions. As tunnel projects extend into deeper and more mountainous terrains, engineers face increasingly complex geological conditions, including high water pressure, intense geo-stress, elevated geothermal gradients, and active fault zones. These conditions pose substantial risks such as high-pressure water inrush, large-scale collapses, and tunnel boring machine (TBM) blockages. Addressing these challenges requires advanced detection technologies capable of long-distance, high-precision, and intelligent assessments of adverse geology. This paper presents a comprehensive review of recent advancements in tunnel geological ahead prospecting methods. It summarizes the fundamental principles, technical maturity, key challenges, development trends, and real-world applications of various detection techniques. Airborne and semi-airborne geophysical methods enable large-scale reconnaissance for initial surveys in complex terrain. Tunnel- and borehole-based approaches offer high-resolution detection during excavation, including seismic ahead prospecting (SAP), TBM rock-breaking source seismic methods, full-time-domain tunnel induced polarization (TIP), borehole electrical resistivity, and ground penetrating radar (GPR). To address scenarios involving multiple, coexisting adverse geologies, intelligent inversion and geological identification methods have been developed based on multi-source data fusion and artificial intelligence (AI) techniques. Overall, these advances significantly improve detection range, resolution, and geological characterization capabilities. The methods demonstrate strong adaptability to complex environments and provide reliable subsurface information, supporting safer and more efficient tunnel construction.

Liyuan Liu, Yaohui Li, Wenzhuo Cao et al.

Rock damage significantly affects coupled thermo-hydro-mechanical (THM) behavior in deep geothermal exploitation through changing thermal and hydrological properties of rocks. For this, a thermo-hydro-mechanical-damage (THMD) coupled model was developed to describe the coupling between rock damage and mechanical, fluid flow and heat transfer fields. The model considers rock heterogeneity, and incorporates the Mohr-Coulomb failure criterion and the maximum tensile stress criterion to evaluate shear and tensile damage. This numerical modeling methodology was first verified against analytical solutions and experimental results, and was then used to simulate the THMD coupling behavior in deep geothermal exploitation. A coupled numerical model was set up to simulate the geothermal fluids extraction and re-injection process in a reservoir at 1 km depth over a 7-year period. Rock damage was found to accelerate the propagation of cold fronts away from the injection well, and have a distinct effect on the performance of geothermal exploitation. When the rock damage was considered, the field injectivity increases by 8.4 times, the range of cooled regions increases by 18.6 times, and the vertical deformation changes by 1.2 times after 7 years of geothermal operations, compared to the scenario where it was not considered. Parametric studies have suggested that thermal contraction dominates the rock damage evolution, and that thermal-induced rock damage only occurs at a sufficiently large temperature difference between fluids injected and the reservoir. This work underscores the importance of accurately accounting for the damage effect on reservoir response during fluid injection activities that cause significant cooling of reservoir rocks.

Ying Zhang, Kai He, Jianming Yang et al.

Rocks with multi-shaped fractures in engineering activities like mining, underground energy storage, and hydropower construction are often exposed to environments where stress and seepage fields interact, which heightens the uncertainty of instability and failure mechanisms. This has long been a long-standing challenge in the field of rock mechanics. Current research mainly focuses on the mechanical behavior, seepage, and energy evolution characteristics of single-fractured rocks under hydro-mechanical coupling. However, studies on the effects of multi-shaped fractures (such as T-shaped fractures, Y-shaped fractures, etc.) on these characteristics under hydro-mechanical coupling are relatively scarce. This study aims to provide new insights into this field by conducting hydro-mechanical coupling tests on multi-shaped fractured sandstones (single fractures, T-shaped fractures, Y-shaped fractures) with different inclination angles. The results show that hydro-mechanical coupling significantly reduces the peak strength, damage stress, crack initiation stress, and closure stress of fractured sandstone. The permeability jump factor (ξ) demonstrates the permeability enhancement effects of different fracture shapes. The ξ values for single fractures, T-shaped fractures, and Y-shaped fractures are all less than 2, indicating that fracture shape has a relatively minor impact on permeability enhancement. Fracture inclination and shape significantly affect the energy storage capacity of the rock mass, and the release of energy exhibits a nonlinear relationship with fracture propagation. An in-depth analysis of energy evolution characteristics under the influence of fracture shape and inclination reveals the transition pattern of the dominant role of energy competition in the progressive failure process. Microstructural analysis of fractured sandstone shows that elastic energy primarily drives fracture propagation and the elastic deformation of grains, while dissipative energy promotes particle fragmentation, grain boundary sliding, and plastic deformation, leading to severe grain breakage. The study provides important theoretical support for understanding the failure mechanisms of multi-shaped fractured sandstone under hydro-mechanical coupling.

Zhixiong Wu, Yijie Wang, Liming Hu

Foam plays a crucial role in conditioning the mechanical properties of coarse-grained soil during earth pressure balance shield tunneling. Experimental findings have shown that an appropriate foam injection ratio improves the workability and compressibility of conditioned soil, while reducing its shear strength under undrained conditions. Understanding how foam operates in soil pores is essential for interpreting these phenomena. This study utilized a theoretical two-dimensional (2D) model to analyze the effects of gas saturation, gas-liquid interface, and gas dissolution on the undrained mechanical properties of foam-conditioned soil. Based on these analyses, a constitutive equation was developed, using the transition void ratio, compression index and contact coefficient as key parameters to describe the relationships among vertical stress σv, void ratio ec, and shear strength τ. The undrained mechanical properties calculated by the 2D model align well with experimental observations, indicating that while foam enhances the bonding force between soil particles, both excessive and insufficient gas saturation, along with larger contact angles, notably undermine this enhancement, resulting in unsuitable workability. A gas saturation of 0.5–0.8 is recommended for soil conditioning. Under typical chamber pressures, the effects of gas-liquid interface and gas dissolution on compressibility and shear strength are negligible. The constitutive equation demonstrates excellent agreement with experimental data, and can well predict the variations in σv-ec-τ. This study contributes to understanding the role of foam in soil pores, and the developed constitutive equation serves as a valuable reference for describing the undrained mechanical behavior of foam-conditioned coarse-grained soil.

Chunhui Song, Caiping Lu, Xiufeng Zhang et al.

Mining-related seismicity poses significant challenges in underground coal mining due to its complex rupture mechanisms and associated hazards. To bridge gaps in understanding these intricate processes, this study employed a multi-local seismic monitoring network, integrating both in-mine and local instruments at overlapping length scales. We specifically focused on a damaging local magnitude (ML) 2.6 event and its aftershocks that occurred on 10 September 2022 in the vicinity of the 3308 working face of the Yangcheng coal mine in Shandong Province, China. Moment tensor (MT) inversion revealed a complex cascading rupture mechanism: an initial moment magnitude (Mw) 2.2 normal fault slip along the DF60 fault in an ESE–WNW direction, transitioning to a Mw 3.0 event as the FD24 and DF60 faults unclamped. The scale-independent self-similarity and stress heterogeneity of mining-related seismicity were investigated through source parameter calculations, providing valuable insights into the driving mechanism of these seismic sequences. The in-mine network, constrained by its low dynamic changes, captured only the nucleation phase of the DF60 fault. Furthermore, standard decomposition of the MT solution from the seismic network proved inadequate for accurately identifying the complex nature of the rupture. To enhance safety and risk management in mining environments, we examined the implications of source reactivation within the cluster area post-stress-adjustment. This comprehensive multiscale analysis offers crucial insights into the complex rupture mechanisms and hazards associated with mining-related seismicity. The results underscore the importance of continuous multi-local network monitoring and advanced analytical techniques for improved disaster assessment and risk mitigation in mining operations.

Y. Ju, Yunhu Lu, H. Abass

In the context of increasing demand for large-scale geological hydrogen storage, maintaining the integrity and sealing performance of salt caverns under cyclic gas storage and release conditions remains a critical engineering challenge. This study presents a laboratory-based experimental investigation into the effects of cyclic storage–release operations on the permeability and structural integrity of rock salt. A custom-designed testing system was developed by integrating a Programmable Logic Controller (PLC) unit into a commercial rock mechanics testing apparatus, enabling real-time monitoring of equivalent permeability and internal damage evolution. Using helium as a surrogate gas, repeated pressurization–depressurization cycles were applied to cylindrical salt samples extracted from the Jintan area in China. Permeability was measured using the pulse decay method, and microstructural damage was assessed via X-ray computed tomography (CT). Results show a noticeable decrease in permeability after 100 cycles, with no order-of-magnitude change after 200 cycles, indicating strong self-healing characteristics of rock salt under low pressure range. Microcrack development was mainly confined to borehole ends, while the bulk material remained largely intact. These findings validate the suitability of salt caverns for hydrogen storage and provide valuable insights for the safe design and operation of underground energy storage systems.

Chuanjun Fan, Jianming Qin, G. Wang

Investigating the construction mechanics of a ventilation tunnel using the TBM (Tunnel Boring Machine) pilot and enlargement method with reliable rock mechanics parameters ensures the safety of on-site excavation operations. Leveraging the construction project of the ventilation tunnel at the Wuhai Pumped Storage Power Station, TGP sidewall forecasting was employed to explore the geological conditions within a 50 m range of the tunnel’s side. A systematic study of the construction mechanics of the TBM pilot and enlargement method was conducted, along with corresponding construction recommendations and engineering applications. This research indicates that sidewall forecasting can supplement the deficiencies in geological exploration reports, with excavation revealing conditions consistent with the forecast. Deformation at the interface, including the arch crown and sidewall, mainly concentrates during the construction phase from the completion of full-section excavation to the beginning of expansion. As the working face advances, the upper rock mass within the ventilation tunnel outline experiences tension, with stress concentration in the shoulder and bottom corner rock masses. The plastic zone before expansion primarily concentrates within the ventilation tunnel outline, shifting to the sidewall after expansion, with the left shoulder’s plastic zone depth slightly exceeding that of the right. The proposed method effectively ensures construction safety, and the research findings have valuable implications for similar projects.

Meimei Wang, Jianwei Zheng, Shanshan Xue

Rock and soil masses in geotechnical engineering projects, such as tunnels, mines and slopes, undergo relative motion, exhibiting mechanical characteristics of solid–fluid transition under critical conditions. This work analyzes the characteristics of the solid–fluid transition interface and the mode of load transfer through biaxial compression particle flow photoelastic experiments on granular materials. The study documents that this interface forms an arch shape, marked by a force chain arch. The granular material exhibits two distinct states depending on its position: below the arch, the granular material is in a solid–fluid transitional state, with bearing capacity reduced, while above the arch, it is in a stable solid state, capable of bearing the overlying rock layer’s load. The presence of the force chain arch alters the direction of the originally downward-transferring load, redirecting it along the trajectory of the arch. Analysis of the force and stability of the force chain arch revealed that the arch shape parameters and boundary loads control the instability of the arch. Changes in the overlying and lateral loads lead to different types of instability of the force chain arch. The findings of the study are crucial for underground engineering construction and for the prevention of geological disasters related to granular material.

Meiyi TU, Shiyu YUAN, Jiangjun CHEN et al.

Objective Mountain restoration is currently one of the major projects in environmental engineering. The backfill formed in artificial slopes is relatively loose and highly susceptible to the impact of rainfall intensity, leading to slope instability. Methods In this study, a combination of numerical simulation method and onsite monitoring technology was used to analyze the stability of artificial slopes formed during the restoration of Dingguanfeng Mountain. By establishing precise geological models, defining material parameters, and setting boundary conditions, the stability coefficients of the slope under the four different rainfall working conditions set were obtained, and the distribution characteristics of the seepage field and deformation field of the slope under different conditions were simulated. A real-time monitoring cloud platform was established on the site to monitor the surface horizontal displacement and deep horizontal displacement of the fill slope on site. The monitoring results were compared with those obtained from numerical simulation to quantitatively assess the slope stability under different working conditions. Results The results indicate that the stability coefficients of the fill slope under different rainfall conditions are greater than the critical factor for interface sliding. Under various working conditions, the pore water pressure at the slope toe and the portion close to the slope surface increases considerably. Seepage channels are mostly developed at the front edge of the slope body and the steep areas of the slope surface, and the stability of these areas is relatively more affected by rainfall. With the increase in rainfall intensity, the maximum horizontal displacement in the middle and lower parts of the slope gradually enlarges. The greater the amount of rainfall infiltrating into the slope within the same time, the more significant the reduction in shear strength, the larger the area with large horizontal displacement, and it gradually extends towards the front and rear edges of the slope. By comparing the numerical simulation results with the data obtained from on-site monitoring, it is discovered that there is a good consistency between them, and the slope is basically in a stable state. Conclusion Henceforth, for the data generated from numerical simulation analyses, they should be combined with on-site monitoring data to conduct a more comprehensive assessment of the engineering stability.

LEI Huayang 1, 2, BAO Yilin 1, FENG Shuangxi 1, 2

The vacuum preloading technology is widely used in the treatment of large-area silt foundations formed by dredging. In order to improve the traditional vacuum preloading reinforcement effects, a method of vacuum preloading combined with alkali residue treatment is proposed for dredging silt foundations. By conducting the indoor vacuum preloading model experiments and microscopic tests, the reinforcement effects and mechanisms are explored and analyzed. The research results show that compared with the conventional vacuum preloading method, the new method has significantly improved the reinforcement effects, with an increase of about 20% in the drainage and surface settlement. After reinforcement, the water content of the soil is reduced by 34.9% from 90%, and the maximum vane shear strength is increased by 1.33 times. Through the SEM and mercury intrusion tests, it is found that the alkali residue can promote particle aggregation, reduce the content of fine particles in the soil, and increase the permeability of dredged sludge. Strong hydration reactions may occur between alkaline slag and clay minerals, generating products. This study provides a theoretical basis for the technological development of improving the vacuum preloading methods and the efficient utilization of alkali residue.

Shenggen HUANG, Mingjian HE

Objective This study focused on the surface energy characteristics of red-bed soft rocks during disintegration in the Shengzhou-Xinchang area of Zhejiang Province. Methods Based on the principle of energy dissipation, this study analyzed the conversion, transfer, and dissipation of energy during the process of disintegration under dry-wet cycles for three groups of red-bed soft rocks, considering different compositions in the study area. This study aimed to explore the law of energy absorption and transformation into surface energy during the process of red-bed soft rock disintegration. Results The results show that the surface energy accumulation of the red-bed soft rock in the study area undergoes three stages with an increasing number of dry-wet cycles: a slow growth stage, a rapid growth stage, and a stable stage. The results also indicate that the higher the content of clay minerals in the red-bed soft rock is, the more surface energy it generates, and the poorer its resistance to disintegration. Conclusion The energy dissipation model proposed in this study provides a reference for the governance of various failure problems of the red-bed soft rock in the Shengzhou-Xinchang area of Zhejiang Province.

Y. Ju, Mian Chen, Yunhu Lu

Generally speaking, the rock formation with creep capability, where rocks undergo continuous deformation under constant stress, are commonly encountered especially in geomechanics, petroleum engineering, and mining science. This phenomenon significantly impacts the stability of underground engineering structures, such as petroleum/geothermal wellbores or the safety of coal mine tunnels. Therefore, investigating formation with viscous property, characterizing its creep behavior, and determining creep parameters are crucial for ensuring safe construction and production. Currently, the study of creep properties primarily relies on laboratory tests. However, rock samples obtained from underground may undergo changes in their physical and chemical properties during coring operation, transportation, and storage processes, potentially introducing discrepancies between the parameters acquired in lab and the actual value. Nowadays, apparatus capable of conducting creep or rock mechanic experiments are typically characterized by large overall dimensions, causing multiple challenges including disassembly, relocation, and poor environmental adaptability. As a result, they are typically restrained to usage in specialized laboratories. To address these limitations, this study employed a self-designed and fabricated true triaxial visualization rock mechanics test apparatus, characterized by rapid assembly, simple operation, compacting structure, etc. This apparatus allows for creep tests under true triaxial stress with only a single hydraulic power source. Moreover, even in unfavorable conditions, image acquisition can be accomplished using a phone camera, whose application has been verified through tests. Therefore, it is highly suitable for field applications in oilfields. Using this apparatus, a variety of creep experiments under different stress levels were conducted. The true triaxial visualization approach proved to be more direct in observing the influence of rock anisotropy/heterogeneity on rock creep. Through a single experiment, we were able to directly obtain creep patterns for different components, significantly enhancing experimental efficiency.

Jun-chao Cai, S. Lu, Kangning Li et al.

Many slabbing rock masses have emerged in hydropower slopes and underground engineering, with the construction of basic engineering and resource development projects along the zone of the Belt and Road. The anti-dip slabbing rock mass is prone to toppling and the degree of slabbing controls the development of toppling deformation. There are a few reports on the mechanical mechanism of rock mass toppling deformation after slabbing. Based on the analysis of the genetic conditions of rock mass slabbing, the influence of rock mass after slabbing on toppling deformation was explored by means of the mechanics method. The toppling bending deflection (TBD) and the toppling fracture depth (TFD) were selected as the analysis indexes, and the response regularity of slabbing on toppling rock mass was analyzed with examples. The results show that the width and thickness of the slabbing rock mass become narrower and thinner, the toppling bending deflection (TBD) increases, the toppling fracture depth (TFD) decreases, and the toppling deformation and failure intensify. The TBD is independent of the width of rock mass slabbing under self-weight, and the change of TBD is slow when the slab beam slabbing number (n) of thickness is <4 and fast when the slabbing number is above 4. The first TFD decreases fast when w is <2.0 m and it tends to be stable when w is above 2.0 m. The first TFD reduces relatively fast with the decrease in the thickness (t) of the slab beam. The result of this study can provide a reference for the treatment and evaluation of slabbing rock mass toppling deformation.

David A. Wood

Derivative/volatility well-log attributes from very few commonly recorded well logs can assist in the prediction of total organic carbon (TOC) in shales and tight formations. This is of value where only limited suites of well logs are recorded, and few laboratory measurements of TOC are conducted on rock samples. Data from two Lower-Barnett-Shale (LBS) wells (USA), including well logs and core analysis is considered. It demonstrates how well-log attributes can be exploited with machine learning (ML) to generate accurate TOC predictions. Six attributes are calculated for gamma-ray (GR), bulk-density (PB) and compressional-sonic (DT) logs. Used in combination with just one of those recorded logs, those attributes deliver more accurate TOC predictions with ML models than using all three recorded logs. When used in combination with two or three of the recorded logs, the attributes generate TOC prediction accuracy comparable with ML models using five recorded well logs. Multi-K-fold-cross-validation analysis reveals that the K-nearest-neighbour algorithm yields the most accurate TOC predictions for the LBS dataset. The extreme-gradient-boosting (XGB) algorithm also performs well. XGB is able to provide information about the relative importance of each well-log attribute used as an input variable. This facilitates feature selection making it possible to reduce the number of attributes required to generate accurate TOC predictions from just two or three recorded well logs.

Wenbo Liu, Hui Zhou, Shuguang Zhang et al.

The initiating condition for the accelerated creep of rocks has caused difficulty in analyzing the whole creep process. Moreover, the existing Nishihara model has evident shortcomings in describing the accelerated creep characteristics of the viscoplastic stage from the perspective of internal energy to analyze the mechanism of rock creep failure and determine the threshold of accelerated creep initiation. Based on the kinetic energy theorem, Perzyna viscoplastic theory, and the Nishihara model, a unified creep constitutive model that can describe the whole process of decaying creep, stable creep, and accelerated creep is established. Results reveal that the energy consumption and creep damage in the process of creep loading mainly come from the internal energy changes of geotechnical materials. The established creep model can not only describe the viscoelastic–plastic creep characteristics of rock, but also reflect the relationship between rock energy and creep deformation change. In addition, the research results provide a new method for determining the critical point of creep deformation and a new idea for studying the creep model and creep mechanical properties.

Chunxin Zhang, Honghu Zhu, Haojie Li

To analyze the pipeline response under permanent ground deformation, the evolution of resistance acting on the pipe during the vertical downward offset is an essential ingredient. However, the efficient simulation of pipe penetration into soil is challenging for the conventional finite element (FE) method due to the large deformation of the surrounding soils. In this study, the B-spline material point method (MPM) is employed to investigate the pipe-soil interaction during the downward movement of rigid pipes buried in medium and dense sand. To describe the density- and stress-dependent behaviors of sand, the J2-deformation type model with state-dependent dilatancy is adopted. The effectiveness of the model is demonstrated by element tests and biaxial compression tests. Afterwards, the pipe penetration process is simulated, and the numerical outcomes are compared with the physical model tests. The effects of pipe size and burial depth are investigated with an emphasis on the mobilization of the soil resistance and the failure mechanisms. The simulation results indicate that the bearing capacity formulas given in the guidelines can provide essentially reasonable estimates for the ultimate force acting on buried pipes, and the recommended value of yield displacement may be underestimated to a certain extent.

Amit Acharya

A methodology for defining variational principles for a class of PDE models from continuum mechanics is demonstrated, and some of its features explored. The scheme is applied to quasi-static and dynamic models of rate-independent and rate-dependent, single crystal plasticity at finite deformation.

Henri Gouin

Invariance theorems in analytical mechanics, such as Noether's theorem, can be adapted to continuum mechanics. For this purpose, it is useful to give a functional representation of the motion and to interpret the groups of invariance with respect to the space of reference associated with Lagrangian variables. A convenient method of calculus uses the Lie derivative. For instance, Kelvin theorems can be obtained by such a method.

Henri Gouin

The invariance theorems obtained in analytical mechanics and derived from Noether's theorems can be adapted to fluid mechanics. For this purpose, it is useful to give a functional representation of the fluid motion and to interpret the invariance group with respect to time in the quadri-dimensional reference space of Lagrangian variables. A powerful method of calculation uses Lie's derivative, and many invariance theorems and conservation laws can be obtained in fluid mechanics.

M. Hasan, Y. Shang, Peng Shao et al.