This paper aims to propose a new method to analyze the stability of a tunnel using P-wave seismic velocity (V_p) with the help of the Tunnel Seismic Prediction 203 plus system (TSP203_PLUS). On one hand, the relationship between Hoek-Brown constants such as the geological strength index (GSI) and the disturbed parameter (D) and V_p is investigated. On the other hand, the displacement of the tunnel is derived using the Hoek-Brown criterion, but it is hard to determine the Hoek-Brown constants because uncertainties are abundant in geomaterials. Fortunately, V_p can be read from TSP203_PLUS, which is an essential approach to predict geohazards in tunnels, and it is widely used during tunnel excavation. A series of parameters such as Young’s modulus, Poisson’s ratio, and the V_p of rocks can be read from TSPwin (the software for processing data in TSP203_PLUS). However, a precise prediction of V_p and other parameters depends mostly on the experience of the engineers. In order to eliminate the uncertainties due to the different engineers, it is reasonable to standardize the parameters as normal variables; then the stability of the tunnel can be calculated based on the response surface method (RSM), and the stability of the tunnel is represented by the probability of failure. To demonstrate the usefulness of this approach, a tunnel located in China is assessed and the results are validated by Monte Carlo simulations. The proposed method provides a convenient and effective method to study the reliability assessment of tunnels.

Geotechnical engineering is dominated mostly by uncertainties, because it always deals with highly variable natural materials. Reliability-analysis approaches emerge as a more reasonable and rigorous way of handling uncertainties. Two-dimensional stability assessment of rock slopes is performed, and the probability of failure of rock slopes against planar sliding is determined using the random fields. Both cohesion and friction coefficient along a discontinuity are treated as a normal random field and are represented by the mean values, standard deviations, spatial correlation lengths, correlation coefficient, and cross-correlation length, which account for the cross correlation between cohesion and coefficient of friction. Several examples are used to verify the proposed approach. The numerical results obtained from the proposed method are in good agreement with the numerical results obtained from Monte Carlo simulations. Moreover, the proposed method provides a new approach to study two-dimensio...

Accurately determining the mechanical parameters of surrounding rock in tunnel design and construction presents a significant challenge due to the complexity of the environment. This study proposes a novel approach for inverting these parameters using an advanced optimization method, the Improved Grey Wolf Optimization (IGWO), integrated with a BP neural network (IGWO-BP). Key enhancements such as cubic chaotic mapping, refraction backward learning, nonlinear convergence factors, and updated position formulas were applied to improve the algorithm’s search efficiency. By optimizing the neural network’s weights and biases, a precise relationship between rock mechanics and displacement was established. The method was validated through a case study of the Lianhua Tunnel (YK37 + 330 section), utilizing field data of crown settlement and peripheral displacement. The approach accurately predicted mechanical parameters, with relative errors below 5.02% for crown settlement and 4.15% for peripheral displacement. These results demonstrate the reliability and practical applicability of the proposed technique for tunnel engineering.

Soil can be amended with cement, lime, fly ash and other curing agents after diesel contamination. In this study, a diesel-contaminated granite residual soil with an oil content of 9% was selected and amended with cement, lime and fly ash as curing agents and their incorporation levels were varied. A straight shear test showed that 6% lime resulted in the best improvement in the contaminated soil, with a cohesive force of 122.1 kPa and an internal friction angle of 27.1°. A disintegration test revealed that the disintegration resistance of the contaminated soil was improved by 6% cement, 20% fly ash and 10% lime, with 10% lime being the most effective. SEM tests revealed that diesel fuel acted as a constant pore fluid to cause significant fragmentation and separation of the granite residual soil from flakes and blocks to smaller agglomerates and fragments. The curing agent, by increasing the physical reaction products, causes the particles to agglomerate, filling the soil pores and enhancing the integrity of the soil, thus improving the soil properties.

Deep-sea-resource development and marine engineering represent cutting-edge global research priorities. As a typical deep-sea region in the Western Pacific, the physical–mechanical properties of the South China Sea’s deep-sea sediments have critical implications for regional and global deep-sea engineering design and the safety assessments of resource exploitation. However, due to extreme environmental conditions and sampling technology limitations, studies on the mechanical behavior and microstructural control mechanisms of sediments in complex marine environments exceeding 2000 m in depth remain insufficient worldwide, hindering precise engineering design and risk management. This study systematically investigates the physical–mechanical properties, microstructure, and mechanical behavior of intact sediments acquired at a depth of 2060 m in the South China Sea. Through physical property tests, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), one-dimensional consolidation, and triaxial shear tests, combined with comparisons with nearshore soft soils and other deep-sea sediments, we acquired the following results: The sediments primarily consist of muscovite, quartz, and calcite. Triaxial shear tests revealed initial dilation followed by shear consolidation, reaching critical conditions with an effective cohesion of 19.58 kPa and an effective internal friction angle of 27.32°. One-dimensional consolidation tests indicated a short principal consolidation time, wherein the consolidation coefficient first decreased under loading before slowly increasing, while the secondary consolidation coefficient stabilized after vertical pressure exceeded 400 kPa. The research results not only provide a direct reference for designing deep-sea engineering projects in the South China Sea, calculating the penetration resistance of deep-sea drilling rigs, and predicting the foundation settlement of offshore wind power but also furnish typical cases and key data support for the study of the mechanical properties of global deep-sea high-organic-matter sediments and engineering applications.