This study summarizes the diagonal reception method adopted for the jacking-pipe passage at Entrance/Exit No.2 of Jinniu Mountain Station on Fuzhou Metro Line4. Beginning with an analysis of the risks associated with rectangular pipe-jacking reception, the paper presents the corresponding risk-control measures and the technical reception options. To address potential hazards during reception—such as mud and water inflow at the breakthrough opening, detachment of the reinforcement body, and excessive ground settlement—supplementary measures including dewatering, isolation piles, and pipe-roof reinforcement were implemented in addition to conventional rotary-jet grouting and curtain sealing. These measures effectively mitigated the risks of leakage and reinforcement peeling during shield reception. During construction, appropriate operating parameters, soil conditioning, timely friction-reduction grouting, secondary grouting, and breakthrough-opening sealing were applied to ensure that ground settlement remained within a controllable range. Based on statistical analysis of monitoring data, the effectiveness of settlement-control measures during construction is evaluated, thereby verifying the feasibility of the reinforcement options and the pipe-jacking reception technologies employed in this project.

Slope stability assessment is a fundamental issue in geotechnical engineering, with earthquakes recognized as one of the most critical triggers of slope failure. Consequently, understanding the seismic stability of slopes and developing effective reinforcement strategies is essential for mitigating earthquake-induced landslide hazards. In this study, a layered slope model is analyzed using the finite-element strength-reduction method to evaluate baseline stability, while seismic effects are examined through the pseudo-static approach. Considering the characteristic failure mechanisms of layered slopes under seismic loading, a lattice-type anchor-rod reinforcement system is proposed. The influence of this system on the stress field, displacement field, and safety factor is investigated under both natural and seismic conditions. The results indicate that the lattice anchor-rod system markedly enhances slope stability, significantly increasing the safety factor in both loading scenarios. Under seismic excitation, the layered slope develops an extensive failure slip surface, with the maximum displacement concentrated at the slope toe.

The composite soil-nailing wall support system is widely adopted in deep excavation engineering due to its strong economic advantages. However, in recent years, an increasing number of distress and failure incidents have been reported for excavations supported by composite soil-nailing walls. This paper examines a project in Shenzhen, detailing the overall excavation conditions, hydrogeological setting, support configuration, and the localized distress observed in a specific section of the composite soil-nailing wall. Based on numerical analysis, the study focuses on identifying the causes of the distress, evaluating the implemented reinforcement measures, and assessing their effectiveness, supplemented by comparative analysis with third-party monitoring data. The results indicate that for vertically excavated composite soil-nailing pits, water infiltration significantly reduces the shear strength of the slope’s geomaterials and markedly weakens the pullout resistance of soil nails, making localized instability highly likely. Introducing one to two rows of low-tension prestressed anchors can effectively control deformation and substantially reduce the risk of local failure. The engineering experience and analytical conclusions presented herein provide valuable reference for similar projects.

This study investigates the slope distress occurring between stations K303+129 and K303+259 of a highway cut. Field investigation, deep horizontal displacement monitoring, and performance testing of existing ground anchors reveal multi-level degradation across the slope, including shearing of inclinometer casings and stress-loss ratios of ground anchors exceeding 85%. The underlying mechanisms driving instability are analyzed in detail. The mechanical parameters of the slip surface were back-calculated using an inverse-analysis approach, and the slope stability and residual sliding force under natural and heavy-rainfall conditions were evaluated with commercial software Geo-slope. To address the identified defects, a combined remediation system comprising H-section micro-piles, ground anchors, and deep drainage holes was proposed. Post-treatment analyses show that the stability factor of safety increased from 1.044 to 1.233 under natural conditions and from 0.983 to 1.152 under heavy-rainfall conditions, demonstrating significant improvement. The findings provide a practical reference for the diagnosis and mitigation of similar slope-stability problems in highway engineering.

This paper presents a comparative analysis of foundation design schemes and corresponding cost implications across different design stages for the Shantou Detention Center service-facility project. In the preliminary design stage, a composite foundation scheme was adopted, in which cement-mixed columns were used for localized ground improvement, followed by a shallow-foundation system. During the construction-drawing stage, however, adjustments to the building layout resulted in changes to the underlying geological conditions, necessitating a redesign to a percussive bored cast-in-place pile foundation. The study highlights that shifts in building location can alter subsurface conditions, requiring timely analytical reassessment and modification of the foundation system. Given the influence of multiple factors—including government management requirements, evolving user needs, and actual construction constraints—engineering technical conditions often change over the course of a project. Project management should therefore be based on real-time engineering conditions rather than rigidly adhering to the principle that later-stage design costs must not exceed earlier-stage budget limits. The findings provide a useful reference for similar engineering projects.

A clear understanding of the instability and movement characteristics of landslides is essential for predicting hazard consequences and formulating effective mitigation strategies. This study examines the Liangshui Village landslide in Zhenxiong County, Yunnan Province, and employs the discontinuous deformation analysis (DDA) method to numerically simulate its failure-movement process. By integrating simulation results with monitored velocity and displacement variations, the staged kinematic behavior of the landslide is systematically analyzed. The results show that the instability process can be divided into four stages: initiation, acceleration, deceleration-deposition, and stabilization. The movement is characterized by pronounced accumulation of displaced material on the gentle platform at the slope toe. The dynamic evolution of the landslide is jointly controlled by topographic conditions and rock-mass properties: elevation differences and slope gradients govern kinetic energy transformation, while weak interlayers and joint-fissure structures accelerate failure and disintegration of the sliding mass. The findings indicate that, when considering variations in terrain and material composition, different types of landslides may exhibit markedly distinct instability-movement characteristics.

The differential settlement of a factory building foundation led to cracking and deformation of the superstructure. To address this problem, a composite reinforcement scheme combining anchor-rod jacked steel pipe piles with in-pile grouting technology is proposed. The paper elaborates on the reinforcement mechanism of this method, provides a systematic description of key construction procedures and quality-control measures, and evaluates the actual strengthening performance through engineering verification. Field results demonstrate that the combined technique of jacked piles and grouting effectively improves the mechanical properties of the surrounding soil and enables rapid settlement control. The verified scheme satisfies both bearing-capacity and deformation-control requirements, while offering advantages such as short construction duration, minimal disturbance to existing structures, significant settlement-arresting performance, and environmental compatibility. Owing to these merits, the method shows strong application potential and practical value, particularly for the foundation rehabilitation of existing industrial plants, and provides an important reference for similar engineering projects.

This study investigates the spatial behavior of a deep excavation supported by a multi-level-single-level combined asymmetric system adjacent to a riverside environment. The No. 11 rectangular foundation pit of the Wuhan Xinhe Bridge project was used as the case study. A three-dimensional finite-element model based on the Hardening Soil model was developed and calibrated using field monitoring data. The excavation process was analyzed to clarify the spatial deformation characteristics of the retaining structure, ground-surface settlement, and basal heave. The results indicate that: (1) A distinct three-dimensional corner effect governs the deformation of the retaining structure, with the influence zone forming a triangular distribution along the sidewall. The corner effect becomes negligible when the horizontal distance from the pit corner exceeds 16.4 m and the depth exceeds 10.5 m.(2) Lateral deformations of the retaining structure show marked spatial heterogeneity. Deep displacements evolve from a cantilever to a bulging profile, peaking near the base. Under asymmetric constraints, top displacements in single-stage sections form a spindle shape, reversing from inward to outward, while multi-stage sections continuously deflect inward, forming a bow shape.(3) Ground-surface settlement outside the excavation is strongly asymmetric. Settlement on the multilevel support side is significantly larger than on the single-level support side. Settlement troughs perpendicular and parallel to the retaining wall exhibit spoon-shaped and arch-shaped profiles, respectively. (4) The vertical displacement inflection depth exhibits a three-stage trend with distance from the excavation corner: initial decrease, subsequent increase, and ultimate stabilization. This trend defines the spatial deformation boundary conditions for riverside deep excavations supported by asymmetric composite systems.

Voids behind tunnel linings are a major cause of structural deterioration and can significantly reduce the composite load-bearing performance of the surrounding rock-lining system. As a key embedded component for reinforcement and repair during tunnel operation, the pressure-resistant sealing performance of reserved grouting devices directly governs the effectiveness of post-construction grouting. In this study, four improved grouting-device prototypes were designed and fabricated, and their performance was evaluated through grouting-continuity and sealing tests. The results show that all four device configurations achieve feasible overall structural layouts and enable zoned grouting between the inner and outer sides of the tunnel waterproofing layer. In sealing tests, Device Scheme 1 exhibited pronounced leakage at the zoned-grouting control valve and switching valve, indicating that assembly precision and interface-sealing design require further optimization. Device Scheme 2 incorporated flexible gaskets at the switching valve, effectively mitigating leakage and demonstrating the feasibility of flexible-gasket sealing, though minor leakage persisted at the control valve. Device Scheme 3 improved the connection structure of the control valve by adopting a bottom-bolt radial anchoring design for the exhaust pipe and optimizing gasket materials, successfully achieving the intended sealing and zoned-grouting performance. Device Scheme 4 integrated the control valve, exhaust pipe, and switching assembly into a unified structure, further enhancing sealing reliability. Considering the complexity of tunnel construction environments and the need to balance on-site assembly conditions with overall sealing performance, Device Scheme 3 is comparatively optimal, while actual engineering applications may select among the schemes based on specific project conditions. The experimental results verify that structural refinements and material optimization effectively enhance the sealing performance of reserved grouting devices, providing technical support for their engineering design and broader application in tunnel lining backfill grouting systems.

High embankment fills constructed on river-terrace landforms often exhibit complex deformation mechanisms, and existing stability-control measures are frequently insufficiently targeted. This study examines a representative 40 m-high embankment section along the Nayong-Qinglong Expressway in Guizhou Province, employing an integrated approach combining multi-point field displacement monitoring with finite-element numerical simulation. The evolution of post-construction settlement and deep horizontal displacement is systematically analyzed. Layered settlement measurements are used to back-calculate the components of total settlement, and overall stability is evaluated using the strength-reduction method, with particular emphasis on identifying zones of concentrated deformation and their governing mechanisms. Results indicate that embankment compression is the predominant contributor to total settlement, accounting for approximately 61.2%, whereas foundation consolidation settlement primarily originates from the 3～5 m thick gravelly soil cover. Deep horizontal displacement is concentrated within two critical zones: the 0～2.5 m fill-gravel interface beneath the first berm, and the 6 m toe-retaining-wall influence zone beneath the third berm. Both zones correspond closely with the equivalent plastic regions identified in numerical analyses. The computed overall stability factor of safety is 1.35, suggesting a limited safety margin. Numerical simulation results exhibit good agreement with field monitoring data, with relative discrepancies maintained within 15%, thereby validating the reliability of the model. Based on these findings, a targeted suite of stability-control measures is proposed, including bidirectional geogrid reinforcement, anti-slide piles, deep drainage holes, and slope interception ditches, supplemented by a three-level dynamic early-warning mechanism.

Geogrid-reinforced ecological concrete, as an emerging slope-protection technology, not only enhances slope stability but also promotes natural vegetation recovery, contributing significantly to ecological balance and environmental improvement. By testing the porosity, compressive strength, and flexural strength of ecological concrete specimens prepared with different water-cement ratios and various geogrid types, the influences of these factors on material performance were analyzed. The results indicate that geogrids can effectively improve both the compressive and flexural strength of ecological concrete, with the 1.5 cm glass-fiber geogrid performing better than the 3.5 cm plastic geogrid. When the coarse aggregate size and water-cement ratio remain constant, the porosity of ecological concrete is only minimally affected by the presence of a geogrid. The strength of geogrid-reinforced ecological concrete increases initially and then decreases as the water-cement ratio rises. Optimal mechanical performance is achieved at a water-cement ratio of 0.35 with the addition of a 1.5 cm glass-fiber geogrid, yielding flexural and compressive strengths of 3.26 MPa and 7.66 MPa, respectively. At this same water-cement ratio, the material also exhibits favorable pore characteristics, with a maximum porosity of 29.7% and an average porosity of 24%.

A finite effective range of soil cover thickness exists for underwater pipe-jacking, within which construction issues such as uplift or lateral deviation—detrimental to pipe stability—can be effectively avoided. Establishing an appropriate cover thickness is therefore fundamental to ensuring construction safety. Using the Tangxun Lake underwater pipe-jacking project in Wuhan as a case study, numerical analyses were performed to evaluate the effective cover thickness for pipe-jacking through lacustrine deposits. The analyses identified both the applicable range and the threshold value of effective soil cover. The results show that when the soil cover above the pipe is insufficient, pronounced uplift occurs in both the pipe and the overlying soil mass. With increasing burial depth, the deformation of the upper soil transitions from uplift to settlement. At greater depths, both the settlement of the upper soil and the uplift of the lower soil gradually diminish. For the Tangxun Lake project, a cover thickness of 8~15 m constitutes an effective range for underwater pipe-jacking. When the pipe depth reaches 15 m, further increases in cover thickness produce only marginal reductions in crown and invert displacements. However, additional cover substantially increases construction difficulty, cost, and duration. Accordingly, 15 m can be regarded as the threshold cover thickness.

During pipeline construction, water-supply and drainage conduits inevitably intersect existing structures. Although temporary support measures are commonly adopted to mitigate the influence of trench excavation on adjacent facilities, such measures can significantly increase construction costs for long-distance pipeline projects extending tens of kilometers. Assessing the excavation-induced response under unsupported conditions is therefore of practical importance. This study examines the section of the Jiangnan Water Plant expansion project where a distribution pipeline crosses the pier foundation of the Fuyang Bridge. Numerical analyses were performed to evaluate the stability of the trench face and the deformation response of the bridge pier. The results show that the safety factor of the excavation face remains approximately 1.3, with a minimum value of 1.289. Unsupported excavation induces soil displacements of less than 3 mm around the pier, and the corresponding stress variations are below 3 kPa. Surface displacement at the inner pier is 1～2 mm smaller than that at the outer pier, and the associated stress change is likewise 1～2 kPa lower. These findings indicate that, for the studied geological and structural conditions, unsupported trench excavation produces limited deformation and stress disturbance to the bridge pier, providing a quantitative reference for similar pipeline-crossing scenarios.

With the rapid expansion of urban infrastructure, the development of underground space has led to a substantial increase in deep excavation projects. To address the limitations of conventional support systems—particularly their non-recoverability and high energy consumption—this study proposes an X-type supported double-row pile system. The system aims to achieve cost savings and environmentally sustainable construction by eliminating the need for internal bracing while ensuring excavation stability and deformation control in accordance with design standards. Using the finite-difference software FLAC3D, numerical simulations were conducted to investigate the stress and deformation behavior of the X-type pile system, and to examine the influence of inclined-pile angle, connecting-beam length, and pile length on its mechanical and deformation performance. The results indicate that the X-type supported pile system exhibits superior performance compared with traditional double-row pile support. Moreover, the effects and underlying mechanisms associated with inclined-pile angle, connecting-beam length, and pile length differ significantly in their contributions to the system’s overall behavior.

As an auxiliary facility of railway construction, spoil disposal sites play a critical role in ensuring the safe operation of railway lines. This study examines the Zhangjiaying No. 2 spoil disposal site along the Pumei Railway. Through field investigation, topographic surveying, and UAV oblique photogrammetry, the current conditions of the site were characterized, and the spoil volume and maximum pile height were obtained using a DEM-based modeling approach. The SLOPE/W and SEEP/W modules of GeoStudio were employed to evaluate site stability, overall and local stability of the spoil mass, and retaining-wall stability under both natural and heavy-rainfall conditions, using the Ordinary method, the Morgenstern-Price method, and the unbalanced force method. The results indicate that all stability factors satisfy the required criteria under natural conditions. Under heavy-rainfall conditions, the overall stability of the spoil mass and the retaining-wall stability remain acceptable; however, certain local areas exhibit marginal stability. To mitigate potential instability, it is recommended to flatten the slope, improve the drainage system, and enhance surface vegetation to prevent sliding or collapse of the spoil mass.

With most open-pit mines in China approaching depletion, an increasing number of operations are transitioning to underground mining. The rock-mass movement and slope-stability problems induced by underground extraction beneath previously mined open pits have become a serious threat to nearby buildings and transportation infrastructure. Excavation of coal seams beneath the pit floor may lead to damage to surface structures and highways. In this study, numerical simulations were conducted for several mining schemes in the Xixi open-pit mine to obtain the surface deformation after extraction in four mining panels. The extents of potential damage were delineated using three indicators: surface tilt, surface curvature, and horizontal deformation. In addition, the safety of highways surrounding the mine boundary was evaluated with reference to roadbed design specifications. The results show that backfill mining significantly reduces surface subsidence and horizontal displacement, effectively confining the deformation zone within the open-pit boundary. This approach enhances the safety of surface structures and provides guidance for highway construction around the mine. The method has been endorsed through expert review and holds substantial economic significance for both the mining group and the city of Fushun.

Reliability analysis of slope stability is essential for improving the rationality of geotechnical design. Using a deep excavation as the study case, a three-dimensional numerical model was established based on its engineering geology, hydrogeological conditions, and excavation-support scheme. The finite-difference strength-reduction method was employed to calculate the slope stability factor. A total of 1 000 sets of soil parameter combinations were generated through Monte Carlo simulation. Based on the computed stability factors, system reliability theory was applied to evaluate slope stability reliability, and grey relational analysis was used to assess the sensitivity of soil parameters. The results indicate that the mean stability factor of the foundation-pit slope is F_s=1.249, with a failure probability of P_f=1.2%. Natural unit weight and cohesion are the relatively dominant factors influencing the stability factor, whereas internal friction angle and cohesion are the primary factors affecting slope displacement. Comparisons with field-measured data were conducted to examine differences in displacement and their underlying causes. This study provides a useful reference for reliability-based slope stability evaluation and support-system design for deep excavations.

Understanding how rainfall and reservoir water-level fluctuations influence slope seepage fields and stability is essential for preventing landslides and ensuring the safe operation of reservoir infrastructure. Based on a reservoir engineering project, a two-dimensional numerical model of a representative reservoir cross-section was established to investigate the coupled effects of rainfall and water-level rise and fall on pore-water pressure distribution, volumetric water-content variation, and the evolution of slope safety factors. The results indicate that during rainfall and rising water-level conditions, the phreatic line migrates from both the slope crest and toe toward the slope interior until full saturation is reached. When the reservoir water level declines, the phreatic line gradually lowers. Rising water levels increase pore-water pressure and volumetric water content within the soil, leading to a higher slope safety factor, whereas falling water levels reduce pore-water pressure and volumetric water content, resulting in a decreased safety factor.

Jiaozhou Bay was formed through tectonic subsidence and Holocene marine transgression, resulting in the widespread distribution of soft marine clay—dominated by silty clayey mud—around the bay. Based on a comprehensive regional engineering-geological database, this study statistically analyzes the physical and mechanical properties of the representative soft-soil layers and summarizes their spatial distribution across the Jiaozhou Bay region, including the SCO Demonstration Zone and the Hongdao Economic Zone. The results indicate that soft soils are mainly distributed in Anzi Wharf, Qianwan Port, the Bonded Zone, and northern Hongshiya in Huangdao District; southeastern Jiulong in Jiaozhou City; Hetao, southern Shangma, and southern Jihongtan in Chengyang District; Bainidi Park in Licang District; and Huanle Binhaicheng and Dagang in Shibei District. Soft-soil thickness generally increases landward from the offshore margin, reaching a maximum of approximately 14.5 m. The soft soils exhibit water content of 20.0~99.5%, specific gravity of 2.68~2.77, natural density of 1.44~2.04 g/cm³, degree of saturation of 72.7~109.7%, void ratio of 0.650~2.591, plastic limit of 10.0~42.2%, liquid limit of 18.0~72.5%, plasticity index of 4.0~44.8, and liquidity index of 0.75~3.72. The compression index, compression modulus, cohesion, and internal friction angle range from 0.20~2.52 MPa^-1, 0.90~6.50 MPa, 1.0~19.9 kPa, and 1.0~19.0°, respectively.

Frequent collapse-type geohazards occur in the red-bed hilly region of eastern Sichuan, posing significant risks to daily production and living activities, particularly in areas experiencing intense rainfall during the flood season. Rainfall is the dominant triggering factor for collapses in this region, yet the associated deformation mechanisms and failure modes vary considerably. Typical failure patterns include bedding-parallel translational collapse, sliding–tensile cracking, and unloading–faulting types. Compared with the relatively abundant research on red-bed landslides, systematic studies and targeted mitigation strategies for collapse hazards remain insufficient. To address this gap, this study focuses on the most common hazard type in the red-bed hilly terrain—bedding-parallel collapses. By analyzing their deformation mechanisms and synthesizing effective disaster-prevention measures, the work provides practical guidance and technical support for disaster prevention, mitigation, and emergency response in eastern Sichuan.

To investigate the damage evolution of deep tunnel surrounding rock subjected to the coupled influences of temperature, seepage, and stress during excavation, a thermo-hydro-mechanical-damage (THMD) coupling model was developed based on thermoelasticity, Biot’s seepage theory, and continuum damage mechanics. The model was numerically implemented using COMSOL Multiphysics, and a Weibull distribution was introduced to characterize the inherent heterogeneity of the surrounding rock. The spatiotemporal evolution of stress, pore water pressure, temperature, and damage fields following tunnel excavation was systematically analyzed. Numerical results show that excavation induces significant stress redistribution, with stress concentration primarily occurring at the crown and sidewalls and gradually spreading outward. Pore water pressure near the excavation face drops sharply, forming a negative-pressure zone, after which seepage adjusts progressively toward a quasi-steady state. The temperature field develops a pronounced radial gradient due to rapid cooling at the tunnel boundary and subsequently becomes more uniform over time. Damage is mainly concentrated along the tunnel sidewalls and propagates from the excavation boundary into the deeper rock mass, with localized zones approaching failure. These findings elucidate the mechanisms governing damage evolution in deep tunnel surrounding rock under multi-physical coupling and provide a theoretical basis for stability assessment and engineering design of deep tunnels in extreme environments.

In deep soft-soil regions, rigid-pile composite foundations have increasingly exhibited basal voids and abnormal inter-pile soil settlement during post-construction service. Using the Chaoshan Ring Expressway project as a case study, this paper investigates the deformation mechanism of pile-soil interaction driven by non-loading factors. A coupled hydro-mechanical numerical model was developed based on site-specific geotechnical parameters to systematically evaluate the respective contributions of groundwater-level fluctuations, under-consolidation of soft soil, and pile-installation disturbance to inter-pile soil settlement. The results indicate that three non-loading mechanisms dominate the observed settlement: (i) increased effective stress induced by abrupt groundwater drawdown, (ii) self-weight consolidation of under-consolidated soft soil, which may reach up to 12 cm, and (iii) long-term dissipation of excess pore pressure generated by soil displacement during pile installation. The consolidation-driven deformation triggered by these factors is identified as the primary cause of basal voids beneath rigid-pile composite embankments. The findings highlight the need to account for long-term hydrological variations and construction-induced disturbances in both design and maintenance. Overall, soil consolidation and deformation induced by non-loading factors constitute the governing mechanism behind void formation in rigid-pile composite foundation embankments.

Expansive soils exhibit pronounced swelling upon wetting and shrinkage upon drying, often triggering slope failures and other geotechnical hazards. Targeted monitoring is therefore essential for effective hazard prevention. This study systematically reviews existing monitoring technologies for expansive-soil slopes, including using GNSS and InSAR for surface displacement monitoring, borehole inclinometers and flexible inclinometers for deep displacement, and techniques for measuring soil water content and matric suction to characterize moisture and hydraulic conditions. Based on this review, a multi-field, three-dimensional automated monitoring system was developed for an expansive-soil slope along an oil and gas pipeline in Guangxi. The system integrates meteorological data, surface and subsurface displacement, moisture and suction parameters, soil pressure, and pipeline strain. Monitoring results indicate that rainfall infiltration is the primary driver of slope deformation and instability, predominantly affecting the shallow 0~3 m soil layer. Slope failure progresses through three stages: slow creep, multi-episode sliding accumulation, and accelerated instability. Soil deformation further compresses the pipeline, causing synchronous increases in pipe stress and strain. Surface displacement acceleration and soil pressure are effective indicators for early warning of impending failure, while variations in water content at different depths can be used to infer potential sliding surfaces within expansive-soil slopes.

Expansive soils are widely distributed across southwestern and northwestern China, and variations in water content exert a pronounced influence on their engineering behavior. Nuclear magnetic resonance (NMR) technology enables nondestructive quantification of water residing in different pore domains of soil. In this study, a series of water-absorption swelling tests were conducted on expansive-soil specimens using an NMR experimental system in conjunction with a conventional consolidation apparatus to investigate the influence of initial water content on swelling behavior. Test results indicate that increasing initial water content suppresses the swelling potential of expansive soil. Moreover, at higher dry densities, the differences in void ratio after hygroscopic swelling among specimens with different initial water contents become more pronounced. Correspondingly, the NMR results show that higher initial water content leads to lower NMR signal peak amplitudes, smaller T-2 values associated with the peak, and reduced area enclosed by the curve and the x-axis. Under high vertical stress, expansive soils with lower dry density and higher water content are more prone to shrinkage.

Expanded-head anchors, owing to their distinctive geometry and load-transfer mechanism, are widely employed in applications such as basement uplift resistance. Based on an actual foundation-pit project in Hefei, a numerical model of the expanded-head anchor-soil interaction was established using the ABAQUS finite-element platform to investigate the uplift bearing behavior under different loading levels. Comparison between field pullout tests and numerical simulations confirmed the validity of the finite-element model through consistent load-displacement responses. Field test results indicate that the deformation evolution of expanded-head anchors under uplift loading comprises an elastic stage, a transitional stage, and a plastic compression-failure stage. Numerical analyses further show that the uplift capacity is governed primarily by the end-bearing resistance mobilized in the soil ahead of the expanded head, resulting in significantly higher pullout resistance compared with conventional anchors. Understanding the load-transfer mechanism and failure modes of expanded-head anchors provides important guidance for the advancement of underground engineering design and practice. 

Since the early 2 000 s, numerous new airport construction and expansion projects have been initiated across Southwest China, with the red-bed strata of the Sichuan-Chongqing region becoming a focal area for such developments. These projects inevitably encounter engineering challenges associated with red-bed mudstone, particularly in zones requiring deep embankment fills to form runway and taxiway subgrades. Because airport pavement foundations must provide adequate bearing capacity, the mechanical properties of subgrade fill—such as strength, California bearing ratio (CBR), resilient modulus, and degree of compaction—must satisfy stringent design specifications. Consequently, the selection of fill materials is highly restrictive, typically requiring Class A fill. However, in many projects, on-site materials fail to meet these criteria. For example, at Leshan Airport, high-quality granular fill is scarce, and importing suitable material would significantly increase construction costs. Meanwhile, large quantities of mudstone are excavated on site, presenting an opportunity for in-situ utilization. Whether this mudstone can be improved for use as subgrade fill is therefore a question of practical significance. To address this issue, a full-scale trial embankment was constructed at Leshan Airport. Tests were conducted to determine the optimal cement content, CBR, subgrade reaction modulus, organic matter content, and other relevant parameters. The results show that mixing mudstone with an appropriate proportion of cement markedly improves its engineering properties. Considering both technical performance and economic feasibility, technical specifications are proposed for using cement-stabilized mudstone as fill for non-airfield pavement subgrade cushion layers. The recommended criteria include: cement content ≥2%, well-graded particle size distribution, maximum particle size ≤6 cm, uniform mixing, eight passes of compaction, degree of compaction ≥98%, CBR≥8%, and subgrade reaction modulus ≥60 MN/m³.

Accurate identification of rocksoil types and their spatial distribution is essential for ensuring construction safety and controlling project costs in urban metro tunneling. Along the Wuhan Metro Line 5 alignment between Pengliuyang Station and Simenkou-Yellow Crane Tower Station, the tunnel must pass beneath She Shan, where extremely hard quartz sandstone is present, and the area is densely built0up with urban structures. After reviewing existing data and consulting specialists, it was determined that conventional borehole drilling could not be fully implemented across the entire section. Therefore, on the basis of detailed geological mapping, a suite of integrated geophysical prospecting methods—including ground-penetrating radar, electrical profiling, and transient electromagnetic sounding—was employed to investigate the distribution of hard rock beneath the densely built urban zone. Comparison with field geological mapping and earlier investigation results indicate that the integrated geophysical survey provides reliable outcomes. The total tunnel length affected by hard rock is approximately 131.8 m. Laboratory testing shows that the uniaxial compressive strength of the hard rock ranges from 153 to 260 MPa, with quartz content reaching 99%. It is recommended that the mining method be adopted for tunnel construction between chainages K11+597 and K11+701.8. In the subsequent section from K11+701.8 to K11+728.8, where self-stability is relatively weaker, roof support should be installed.

The mechanical characterization of sandy cobble mixtures is challenging due to their heterogeneous lithology, loose structure, and large particle size. Obtaining reliable strength and stiffness parameters through conventional laboratory and in-situ tests is both technically difficult and costly, often leading to significant uncertainty in engineering design. In this study, strength and modulus parameters of sandy cobble soils were back-calculated using a plastic-hardening constitutive model in FLAC3D, based on plate load tests performed to failure. The results were compared with those obtained using the Mohr–Coulomb model. Numerical back-analysis indicates that the plastic-hardening model better captures the stiffness-degradation behavior characteristic of sandy cobble materials. The inferred internal friction angle is notably high, typically ranging from 50° to 60°, and the elastic modulus is also substantial, on the order of 200~300 MPa—significantly exceeding the parameter values commonly adopted in engineering design. It is therefore recommended that design practice appropriately increase the strength and stiffness parameters for sandy cobble soils, and that numerical back-analysis be used as an effective supplementary approach for parameter determination.

This study examines an existing metro tunnel adjacent to a deep excavation in Guangzhou’s granite strata, using field-measured data to characterize tunnel deformation during excavation. Results show that the retaining system could not effectively cut off hydraulic connectivity, causing substantial tunnel settlement, with a maximum value of 42 mm. Ensuring tunnel safety therefore requires strict control of groundwater cutoff performance to avoid large external water-level fluctuations. Because the station structure is stiffer than the running tunnel, stiffness mismatch produced notable differential deformation near their connection, warranting intensified monitoring. Additionally, grouting near metro tunnels in granite areas can induce uplift deformation and must be rigorously controlled. These findings provide guidance for safe excavation and tunnel protection in granite regions.

To investigate the effects of the water-to-solid ratio, fly ash-soil ratio, and fly-ash replacement level on the performance of flowable backfill materials, dredged sludge was used as the fine aggregate and combined with fly ash and cement as the cementitious components to prepare flowable stabilized soil. Results from flowability and mechanical tests indicate that the water-to-solid ratio directly governs both the flowability and strength of the material: increasing the water-to-solid ratio enhances flowability but reduces strength. An increase in the fly ash-soil ratio leads to varying degrees of improvement in flowability and strength. When the fly ash-soil ratio increases from 0.2 to 0.3, flowability and 28-day compressive strength rise markedly, by 18% and 130.2%, respectively. As the fly-ash replacement level increases, flowability gradually improves, the 7-day compressive strength decreases, and the 28-day strength first declines and then increases.

Expressway subgrades constructed in permafrost regions are highly susceptible to deformation and distress under repeated freeze-thaw cycling, particularly in environments characterized by severe climate and poor engineering-geological conditions. To address the subgrade problems observed along the permafrost sections of the Gongyu Expressway during operation, this study investigates crushed-rock ventilated subgrade gravel and stone-slag cushion materials through a combination of field surveys and laboratory testing. The mechanical behavior, soluble-salt content, capillary rise characteristics, permeability, and frost-heave response of the materials were systematically evaluated. The results indicate that the crushed-rock ventilated subgrade fill exhibits favorable gradation that complies with design specifications for permafrost regions. The soluble-salt content (0.057%~0.080%) exerts negligible influence on soil structure and frost-heave potential. The measured capillary rise height (26.0~29.0 cm) and strong capillary rise height (9.9~12.1 cm) both satisfy the performance requirements for permafrost-region subgrades. However, material saturation significantly reduces subgrade stability and may induce multiple forms of distress. These findings provide a scientific basis for evaluating and improving the long-term stability of expressway subgrades in permafrost environments and offer technical support for the maintenance and safe operation of the Gongyu Expressway.

This study examines the effects of siltyclay incorporation on the mechanical and durability performance of foamed lightweight soil. A series of laboratory tests—including unconfined compressive strength (UCS), splitting tensile strength, and flexural strength—were conducted on specimens prepared with varying siltyclay contents. Durability was further evaluated through dry-wet cycling and freeze-thaw cycling tests. The results show that increasing the siltyclay content leads to a progressive reduction in UCS, splitting tensile strength, and flexural strength. Based on the 28day UCS criterion, the siltyclay content should not exceed 30% for foamed lightweight soil used in subgrade beds and should remain below 50% for embankment applications. The incorporation of silty clay also impairs dry-wet cycling resistance and frost durability; higher siltyclay contents accelerate the decline in the dry-wet strength coefficient and increase compressivestrength loss after freeze-thaw cycling.

This study investigates the disposal and resource reutilization of muck generated from slurry shield tunneling on the Taizhou Metropolitan Railway S2 Line. A low-carbon composite solidification material, formulated primarily from slag, fly ash, and cement, was developed to modify shield-excavated waste soil for reuse as synchronous grouting material. Laboratory experiments were conducted to assess the fluidity, unconfined compressive strength (UCS), and microstructural characteristics of the grouting material produced using the proposed solidification system. The results demonstrate that the solidified and modified shield muck can effectively substitute conventional synchronous grouting materials. Under the optimal mix design, the slurry exhibits a 6 min fluidity of 200 mm, a 30 min fluidity of 160 mm, a 2 h bleeding rate of 1.4%, a 28 day stone formation rate of 98.7%, and a 28 day compressive strength of 2.53 MPa. Microstructural analyses further reveal that the solidification mechanism is governed by the synergistic effects of alkali activation and hydration reactions, which generate CSH gel and ettringite, providing both cementation and pore-filling functions.