This study investigates the impact resistance of rammed earth (RE) materials, unstabilized and stabilized with cement and alkali-activated slag (AAS). Seven RE mix designs were developed, including one unstabilized reference mixture, four cement-stabilized mixtures containing 2.5 wt.
Natural fiber-reinforced polymers (FRP) offer a potential alternative for strengthening applications, specifically in cases where the costly nature of synthetic FRP composites is a worry. This work investigates the effects of basalt fiber-reinforced polymers (BFRP) confinement on flexural behavior, peak loads, and bond strength enhancement by conducting four-point bending tests on simply supported reinforced concrete (RC) beams. Large-scale beams were tested in two groups to differentiate lap splice length. Group 1 beams incorporated a lap splice length of 20db, whereas a 30db lap splice length was used in Group 2 beams (where db is the diameter of lap spliced bars). The findings show that BFRP confinement significantly affects flexural stiffness, improves ultimate strength and ductility. Peak load improvement varies with lap splice length, with Group 1 beams showing up to 80.95
Geotechnical exploration is a critical technology for acquiring subsurface information, exploiting resources, and ensuring engineering safety. However, traditional exploration methods face significant challenges in extreme environments, such as the deep seas, outer spaces, and deserts. These methods often suffer from high power consumption, poor adaptability to different environments, and complex operations. Biomimetics offers new solutions to these challenges. Bio-inspired self-burrowing probes have emerged as a promising tool by mimicking the efficient, low-energy underground movement of biological organisms. This paper focuses on the emerging interdisciplinary field of bio-inspired self-burrowing probes and systematically reviews recent research progress. First, we summarized the biological burrowing mechanisms used for developing self-burrowing probes, and classified these mechanisms into three categories: leaving a cave after burrowing, organisms interact with soil to burrow, and assisted resistance reduction strategies. Second, we categorize current research methods and key technologies. Finally, we analyze major challenges and propose future research directions. This paper concludes that breakthroughs in bio-inspired self-burrowing probes depend on the deep integration of geotechnical engineering, robotics, and materials science.
As underground space continues to be developed, tunnels are inevitably affected by new tunnel construction, threatening operational safety. This study adopts numerical simulation to study the longitudinal response of existing tunnels under different spatial positions and evaluate the tunnel safety of bearing capacity. Then, based on measured data, a long short-term memory (LSTM)-Attention model was developed as a predictive model for safety control throughout the construction process. The importance of tunnelling parameters was quantified, and their dynamic nonlinear influence mechanisms revealed. Results show that there are complex coupling effects during the construction of the new twin tunnels, and the LSTM-Attention model achieves 96.42
Near-fault pulse-like ground motions, characterized by high-energy velocity pulses, pose a significant threat to the seismic safety of underground structures. However, traditional seismic fragility analysis often relies on incremental dynamic analysis using scaled ground motions, which may distort the inherent distance-dependent spectral features of near-fault records. This study proposes a data-driven seismic fragility assessment framework for horseshoe-shaped tunnels utilizing Multiple Stripes Analysis (MSA) and ensemble learning architectures. A high-fidelity numerical model of the horseshoe-shaped tunnel is established, and MSA is adopted with unscaled ground motion records to preserve the inherent physical integrity of pulse-like signals. Based on this model, a large-scale dataset is generated through nonlinear dynamic simulations. Three distinct ensemble learners, Random Forest, Extreme Gradient Boosting, and Categorical Boosting (CatBoost), are developed as surrogate models to predict damage measures (DM) based on ground motion intensity measures (IMs). Results demonstrate that the CatBoost model achieves superior predictive performance, effectively capturing the complex nonlinear mapping between ground IMs and DM. Shapley Additive Explanations analysis quantifies the contributions of various IMs, revealing that velocity-based and energy-based indicators exhibit higher importance under pulse-like motions. Finally, seismic fragility curves are derived, showing good consistency with numerical results. The proposed framework provides a reliable and computationally efficient tool for the rapid seismic risk screening of tunnels in near-fault regions.
The excavation of municipal solid waste landfill has generated numerous heavy metal (HM) contaminated humus soil. The humus soil can be used as the slope cover material to reduce rainwater infiltration after HM remediation and hydraulic properties improvement. This study is intended to explore the impacts of enzyme-induced carbonate precipitation (EICP) on both the immobilization of HMs and the enhancement of hydraulic properties in humus soil. The soil water retention curve (WRC), saturated permeability coefficient (ks) and exchangeable HM concentration were measured, respectively. The results show that EICP can reduce the exchangeable HM concentrations to meet standard requirements through promoting HM carbonate precipitation. The carbonate precipitations mainly form in soil macro-pores, leading to a decrease of more than one order of magnitude in ks and more obvious bimodal feature of WRC. The soil water retention ability can be improved through increasing the air-entry values for macro- and micropores, simultaneously reducing the desorption rate of macro-pores.
This study proposes a fiber-reinforced polymer (FRP)-ultra-high performance concrete (UHPC)-steel double-skin tubular beam (DSTB). The beam exhibits excellent load-bearing capacity, deformability, and durability, making it a promising option for bridge construction. However, the flexural behavior of the beam is significantly influenced by the effectiveness of the shear connectors installed at the steel–UHPC interface. Therefore, this study experimentally investigates the shear behavior of a specific type of stud shear connector using 26 push-out specimens. The test results reveal that the maximum slip values (Smax) of the specimens range from 6.20 to 12.04 mm, satisfying the ductility requirements specified in Eurocode 4. Shear capacity increases with greater glass FRP tube thickness: a 12.3
Traditional tunnel impact resistance support systems face a contradiction between sufficient structural stiffness for stability and adequate energy dissipation capacity for large deformations. To overcome this limitation, a “rigid-flexible-rigid” sandwich steel structure containing energy-absorbing materials (SSCE) is proposed. Theoretical modeling and numerical simulations were conducted to investigate the impact resistance performance of three SSCE configurations: parallel-arc wavy SSCE (Type I), flat plates SSCE (Type II), and staggered-arc wavy SSCE (Type III). Results demonstrate that the SSCE effectively disrupts wave coherence and prolongs the energy dissipation path through multiple mechanisms including interface reflection and refraction, viscoelastic energy dissipation in rubber layers, and wave scattering from wavy geometry. In particular, the impact resistance performance of the Type I SSCE is significantly superior to that of the other two structures. At the monitoring points in the deep rock mass beneath the SSCE, the peak stress wave velocity decreases to 0.03 m/s for Type I, compared to 0.24 m/s for Type II and 0.41 m/s for Type III, the peak maximum principal stress decreases to 8.43 MPa for Type I, compared to 30.09 MPa for Type II and 62.20 MPa for Type III, and the peak displacement decreases to 0.00065 m for Type I, compared to 0.001 m for Type II and 0.00275 for Type III. This research provides a promising solution for enhancing tunnel seismic resilience in active fault zones.
Deep conical footings are used in several civil engineering situations, particularly offshore and in fractured rock terrains, but the study on their bearing behaviour on Hoek–Brown rock masses is limited. In this study, the ultimate resistance of such footings is examined through finite element limit analysis within an axisymmetric setting. The Hoek–Brown criterion is adopted to represent the nonlinearity of jointed rock, and a wide range of geometric and material parameters is explored. The results show how these factors influence the collapse mechanism and the bearing capacity factor, often in ways that differ from conventional soil-based interpretations. A physics-informed data-driven model is developed to strengthen these insights by embedding a genetic programming (GP) algorithm to evaluate the bearing capacity factor. This approach leverages the symbolic-regression capability of GP to automatically construct an explicit nonlinear relationship between the input variables, thereby unifying data-driven modelling with physical constraints. Results demonstrate that, under similar conditions, the proposed model obtained the a coefficient of determination of 0.9721 in training, 0.9705 in testing and 0.9727 in validation phase respectively. Overall, the findings fill a noticeable gap in existing work on conical footings and offer practical guidance for applications where rock conditions dominate the foundation response.
This study investigates the influence of relative density on the mechanical response and stress–dilatancy behavior of biocemented coral sand through consolidated drained triaxial compression tests. Specimens were prepared at three relative densities (Dr = 20
Enzyme-induced calcium carbonate precipitation (EICP) has attracted significant attention owing to its flexible utilization of resources and relatively low biological complexity. Despite its broad potential applications, the relationship between particle morphology and treatment efficacy remains underinvestigated. This study investigates the micro-scale characteristics of EICP and their influence on macro-scale hydraulic properties of sand aggregates. Spherical, near-spherical, and angular silica sands in four size fractions (0.3–0.45, 0.45–0.6, 0.6–0.9, and 0.9–1.0 mm) are employed as variable sand aggregates to assess the alterations in permeability, porosity, and precipitation efficiency as the EICP grouting duration increases. The research indicates that as the grouting cycles increase, the permeability reduction is more pronounced in angular and near-spherical sand. Spherical sand experiences the least reduction in permeability and porosity. Furthermore, for sands of the same shape, the smaller sand exhibits lower porosity after identical treatments. The change in CaCO3 content follows the porosity trend, being lower in spherical sand and higher in smaller-sized sand. Fine-grained aggregates are more sensitive to changes in permeability caused by CaCO3 accumulation. However, spherical particles treated by microbial-induced carbonate precipitation (MICP) exhibit higher CaCO3 content compared to angular and near-spherical sands. This disparity suggests that although MICP and EICP may appear similar, they have fundamentally distinct precipitation mechanisms.
The synergistic application of polypropylene fibers and microbially induced calcite precipitation (MICP) effectively bonds calcareous sand particles and fills inter-particle voids, enhancing both strength and ductility to improve the engineering properties of calcareous sands. A series of unconfined compression tests were conducted on samples of calcareous sand treated with fiber-MICP to investigate the effects of fiber content and fiber length on calcium carbonate content, stress–strain behaviors and unconfined compressive strength. The microstructural characteristics and synergistic reinforcing mechanisms of the fiber-MICP-treated samples were investigated through scanning electron microscopy (SEM) analysis. The imaging results demonstrate that the polypropylene fibers contribute to load-bearing and enhance the bacterial adsorption, promoting additional CaCO3 formation and thereby improving the strength and ductility. The optimal fiber content and fiber length were determined to be 0.2
Post-grouting technology is an effective method to enhance the bearing performance of the pile foundation, where cement is the most commonly applied due to outstanding performance. However, cement production accounts for a relatively high proportion of global carbon dioxide emissions, which doesn’t agree with the dual carbon target. Geopolymer is a green and sustainable material, since consisting of natural minerals rich in aluminosilicate and industrial waste. To promoting the application of geopolymer post-grouting technology, this study, based on the actual stress environment of post-grouting bored piles, explores the influence laws of mudcake, grouting volume, grouting pressure, interfacial roughness, normal stress, and grouting material on the shear characteristics of the geopolymer post-grouting concrete–soil interface through the interfacial shear test, and the shear stress–displacement curves are fitted by using a hyperbolic function model. The results showed that the shear stress–displacement curves conformed to the hyperbolic model, with shear stress–displacement behavior following Mohr-Coulomb failure criteria and showing shear hardening. The presence of mudcake significantly reduced the interfacial shear strength, but geopolymer grouting enhanced the interfacial shear strength by 0.52 to 1.66 times and the cohesion by 1.09 to 2.24 times compared with the ungrouted treatment. Sufficient grouting volume and normal stress mitigate mudcake’s adverse effects. Geopolymer grouting improves interface shear strength 1.45 to 2.41 times more than ordinary Portland cement. This study provides theoretical insights and a scientific basis for geopolymer post-grouting pile application, offering an eco-friendly solution to enhance foundation performance.
Recycled waste glass (RWG) is rarely used as fine aggregate in geopolymer mortar due to its susceptibility to alkali-silica reaction under high alkalinity. Therefore, this study employs low-alkalinity Na2CO3-activated geopolymer mortar, which allows for the use of RWG as a replacement for river sand as fine aggregate. Eight geopolymer mortar mixtures were prepared to investigate the effects of RWG replacement ratios (0
Heavy metal contamination, particularly lead (Pb), poses severe threats to ecosystems due to its persistence and bioaccumulation. This study investigates the remediation of Pb-contaminated soil using bio-augmented microbial induced carbonate precipitation (MICP). The effects of Pb concentration and soil depth on bacterial activity (viable cell counts and urease activity) were evaluated. Furthermore, the impact of different calcium sources and Pb concentrations on immobilization efficiency was assessed via unconfined compressive strength (UCS) tests. The results indicate that the bacterial tolerance threshold for Pb is 50 mmol/L, beyond which the MICP process is significantly inhibited. However, within this threshold, bio-augmented MICP effectively enhances soil strength, achieving a UCS of 0.94 MPa in soil with 50 mmol/L Pb. Microstructural and physicochemical analyses reveal that the remediation mechanism involves the precipitation of carbonate, co-precipitation, and the transformation of macropores into capillary pores. Notably, this study elucidates the distinct advantages of bio-augmentation, particularly its robust tolerance to Pb toxicity and sustained mineralization capability, in reducing the bioavailability of Pb in contaminated soil matrices.
Modern steel erection relies on two main connection methods, welding and bolting, which can be expensive field activities and have remained unchanged for nearly a century. To achieve savings in both weight and cost, increased construction effectiveness and higher steel reuse, a novel type of toothed steel connections with the use of precise, advanced manufacturing methods in waterjet or laser cutting has been established that is based on an interlocking approach to connect steel components that have exactly cut ends. This paper presents testing and finite element analysis (FEA) studies of three unique flange plate geometries of the toothed steel connections failing in tension. Tensile tests were carried out on six samples of the toothed flange connections for each of the three geometries and the digital image correlation (DIC) method was utilized to attain axial displacement. The observed key test results, including load—displacement responses, yield loads, failure loads and modes, were fully presented. Strain contours of the connection geometries with the use of the DIC technique at early stage loading and near ultimate failure were also presented. The experimental program was accompanied with a numerical modeling program, in which finite element models were first created in Abaqus structural analysis software and compared against the test results. Based on the tests and numerical data, the performance and the capacity of the three unique flange connections were assessed. The FEA results agreed very well with the test results, indicating that the numerical simulations can accurately predict yield, ultimate load capacities and failure modes of the toothed connections. The numerical models characterized thoroughly the predicted stress distributions within the connections. For capacity-based design, the second flange connection (CON2) geometry could be adopted in beam tensile zones due to its better overall performance.
Elastic–plastic Finite-Element analysis of notched components is computationally expensive for probabilistic design. To this end, we develop Machine Learning (ML) surrogates trained on linear elastic stress to predict nonlinear elastic–plastic responses. Using Latin Hypercube Sampling, we generate datasets spanning realistic material and geometric variations. Four ML algorithms are compared, namely Deep Neural Networks, Random Forest, Gradient Boosting (GB) and Support Vector Machines, with GB providing the highest accuracy. The computationally efficient workflow eliminates iterative convergence checks, enabling large-scale probabilistic assessment. A variance-based Sobol sensitivity analysis shows that linear von Mises stress and cyclic hardening coefficient explain ∼90
The insufficient early strength and hydraulic conductivity of cemented soil can significantly impact the quality of deep cement mixing (DCM) walls, particularly in water-rich sandy silt regions. To enhance the early engineering performance of DCM walls, industrial by-products (IBPs) such as soda residue (SR), and other additives such as bentonite and water glass (WG) were used. Unconfined compression strength (UCS) and hydraulic conductivity tests were conducted to assess the strength and hydraulic conductivity of the improved cemented soil. Microstructural and mineralogical tests were performed to reveal the mechanisms of SR, bentonite, and WG. The results indicate that adding SR introduces sulfate and chloride ions into the reaction system, thereby promoting the formation of hydration products. However, when the SR content exceeds 8
This study investigates the long-term durability of agar-treated recycled glass sand (ARGS) through unconfined compressive strength (UCS) testing, the pocket erodibility test (PET), and thermogravimetric analysis. The effects of various curing conditions, wet–dry cycles, and pH environments on the mechanical properties of ARGS were systematically evaluated. The results indicate that ARGS exhibits favorable mechanical performance under controlled conditions. UCS testing revealed that strength increased with curing time at room temperature. However, elevated temperatures and exposure to natural environmental factors, such as ultraviolet and precipitation, accelerated agar gum degradation, leading to a reduction in strength. Wet–dry cycling tests demonstrated a gradual decline in strength, yet ARGS retained approximately 50
This work investigates the potential replacement of natural sand within cement mortar via the use of recycled sand derived from excavation waste, construction and demolition waste and concrete waste. To study the mechanical properties such as compressive strength, flexural strength, hardened density, ultrasonic pulse velocity, and durability characteristics, a series of mortar mixtures is prepared by using different percentages of recycled sand (0
