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Addressing the challenge of large deformation in soft rock tunnels is an urgent imperative. The conventional support method is mainly passive or low-stress compensation support, which proves inadequate in effectively managing the large deformation disaster of soft rock under complex geological conditions. This paper focuses on three representative soft rock tunnel scenarios characterized by slate, schist, and metamorphic rock lithologies. The primary objective is to conduct a comprehensive comparative analysis of the efficacy of the NPR (negative Poisson's ratio effect) anchor cable high preload support system based on the excavation compensation method. The results indicate that the NPR high preload support method adeptly controls large deformation disasters in soft rock, maintaining tunnel surrounding rock deformation within 300 mm (<3%). To achieve efficient high-stress compensation through high preload, supporting technologies should be designed for different geological conditions, exemplified by the implementation of double-gradient grouting technology in the Tabaiyi tunnel. This paper comprehensively validates the effectiveness of the NPR high preload support method in mitigating large deformations in soft rock and establishes a foundation for future engineering endeavors. [ABSTRACT FROM AUTHOR]

In this study, a novel debris flow resisting structure is proposed that incorporates negative Poisson's ratio (NPR) cables to unite a flexible net and a rigid barrier; this structure is referred to as the NPR barrier. The NPR barrier attempts to utilize the mechanical properties of the NPR cable—the constant resistance and large deformation—to convert the impact into particle friction resistance and support force. NPR cables can effectively improve the performance of the resisting barrier. To investigate the mechanical response of an NPR barrier, physical experiments are conducted on a debris flow impacting an NPR barrier at two distances with four volume fractions. The experimental results reveal that the impact model of a debris flow with an NPR barrier is a hybrid model that simultaneously incorporates both runup and pileup mechanisms. During the buffering, run-up, and backflow-depositional stages of the debris flow, the NPR cables correspondingly demonstrate a sharp increase in resistance, slight decrease in resistance, and constant resistance, respectively, effectively transforming the impact into resistance. The relationship between the buffer force and impact force exhibits an inverse correlation as the material volume fraction increases. When the material volume fraction increases from 40 to 70%, the buffer force significantly increases by 73.4%, and the impact force substantially decreases by 35.6%. Finally, the calculation methods for the impact force, NPR cable tension, and buffer force are discussed. This study represents an attempt to generate novel insights into the structural optimization of debris flow control systems. Highlights: A novel debris flow barrier, which incorporates Negative Poisson's ratio (NPR) cables, a flexible net, and a rigid barrier, is proposed and referred to as the NPR-anchored barrier (NPR barrier). The impact model of a debris flow with an NPR barrier is a hybrid model that simultaneously integrates both run-up and pile-up mechanisms. The NPR barrier utilizes the constant resistance and large deformation properties of the NPR cable to achieve a sustained equilibrium of impact load and to enhance the efficiency of dissipating impact energy. The mechanical response properties of the NPR barrier have been validated through physical experiments and mechanical calculation analyses. [ABSTRACT FROM AUTHOR]

The control of large deformation problems in layered soft rock tunnels needs to solve urgently. The roof problem is particularly severe among the deformation issues in tunnels. This study first analyzes the asymmetric deformation modes in layered soft rock tunnels with large deformations. Subsequently, we construct a mechanical model under ideal conditions for controlling the roof of layered soft rock tunnels through high preload with the support of NPR anchor cables. The prominent roles of long and short NPR anchor cables in the support system are also analyzed. The results indicate the significance of high preload in controlling the roof of layered soft rock tunnels. The short NPR anchor cables effectively improve the integrity of the stratified soft rock layers, while the long NPR anchor cables effectively mobilize the self-bearing capacity of deep-stable rock layers. Finally, the high-preload support method with NPR anchor cables is validated to have a good effect on controlling large deformations in layered soft rock tunnels through field monitoring data. [ABSTRACT FROM AUTHOR]

Background: Earthquakes and landslides pose significant threats to human safety and property, necessitating early warning systems. However, the high construction costs of earthquake early warning systems present a challenge. Purpose: Landslide warnings are more prevalent, so linking them to earthquake warnings could address cost concerns. Hence, it is crucial to validate the feasibility of utilizing GNSS landslide monitoring as assistance for earthquake early warning systems. Methods: This paper analyzes acceleration anomaly data from 31 GNSS landslide monitoring points near the epicenter of the May 2, 2023, MW = 5.2 Baoshan earthquake in Yunnan. The response time was determined as the time difference between an earthquake's occurrence and GNSS's acceleration anomalies. This calculation helps measure the time delay and sensitivity between these two events. Data were obtained from the geological disaster monitoring and early warning management system. Results: GNSS landslide monitoring showed high sensitivity to nearby earthquakes. The fastest response time among the 31 data points was 8 seconds, while the slowest was 56 seconds, all falling within the one-minute mark. A linear correlation was found between acceleration anomaly response time and distance from the epicenter, indicating the feasibility of GNSS landslide monitoring-assisted earthquake monitoring. Conclusion: A proposal is made for a GNSS landslide monitoring cluster to establish a multi-dimensional landslideearthquake disaster warning system. This approach offers new methods for combining earthquake and landslide early warning systems, leveraging existing infrastructure for cost-effectiveness and enhancing disaster preparedness. [ABSTRACT FROM AUTHOR]

2G-NPR bolt (the 2nd generation Negative Poisson's Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has significant effects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under different tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verified by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt. [ABSTRACT FROM AUTHOR]