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The precursors that appear when geological disasters occur are geotechnical deformations. This paper studies the TDR (Time Domain Reflection) measurement technology for the distributed measurement of geotechnical deformation using parallel spiral wire as a sensor, which is used for monitoring and early warning detection of geological disasters. Based on the mechanism of the electromagnetic field distribution parameters of the parallel spiral sensing wire, the relationship between the stretching amount of the parallel spiral wire and the change in its characteristic impedance is analyzed. When the parallel spiral wire is buried in the soil, the geotechnical deformation causes the parallel spiral wire to be stretched, and according to its characteristic impedance change, the stretching position and the stretching degree can be obtained, thus realizing the distributed measurement of geotechnical deformation. Based on this principle, the TDR measurement system is developed, and a local single-point stretching amount and stretching positioning experiment are designed for the parallel spiral sensing line to verify the effectiveness of the sensing technology and the usability of the measurement system.

The seismically sensitive soft sediment deformations of Karewa Group have been geotechnically analysed to explore the status and frequency of past Quaternary earthquakes in Kashmir valley, India. The detailed studies were performed to establish the sequences of sedimentary structures in general and deformed structures in particular in view of geotechnical parameters. For the purpose the collected sediments from different deformed zones were analysed as per American Standard of Testing Materials for determination of size gradations, liquid limit, plastic limit and flow indices. The studied sequences of deformations were established in space and time by using empirically relationship. The structural architectures of sedimentary features (cross-beddings, massive beddings/loads) reveal the fluvial environments of fluctuating energy conditions for formation of sediment successions. In addition, the sandwiched-zonations of some peculiar structures preserved in the litho-succession may be formed through mechanism different from sedimentations. The size distribution of sediments from sandwiched-zone exhibits medium to fine sands and silt with sorting coefficients ranging from 1.21 to 2.54, coefficient of uniformity ranging from 1.26 to 3.6 with some exceptional values like 5.0, 16.6 and coefficient of curvature ranging from 0.67 to 1.80. The sediments of the same zone show the values of liquidity index ranging from 0.16 to 0.88 and plasticity index ranging from 3.69 to 18.57 with low blows values. These above size sensitive geotechnical parameter values show the higher flow indices and least resistance to flow. The sediments of the peculiar structural zone with characteristically higher flow indices and low resistance support the formation of the soft-sediment structures under seismic stress condition. The demarcated sandwiched zones with such conditions at the time frame of 1,06,566.6 years, 93,245.8 years and 54,502.8 years ago from recent appears to supports three prominent earthquake events (I, II and III) in the geological history of Quaternary deposits around Kashmir Valley, India.

This chapter describes the observables and the operation principles of various geotechnical instrumentations for deformation monitoring. It discusses the advantages and disadvantages (or limitations) of various geotechnical instrumentations for deformation monitoring. The geotechnical and structural techniques of deformation monitoring mainly focus on monitoring and analysis of hydroelectric dams. The chapter discusses the various applications of geotechnical monitoring techniques, using extensometers, four‐pin gauges, joint meters, plumblines, inclinometers, tiltmeters, fiber‐optic sensors (FOS), and micro‐electro‐mechanical system (MEMS) sensors. In Geomatics, the design of monitoring schemes is usually done based on the criteria such as precision, reliability, and overall cost of measurements. The chapter identifies the differences between geotechnical and geodetic deformation monitoring schemes. It explores accuracy specifications for various geotechnical instrumentations with regard to deformation monitoring. The chapter explains how geotechnical monitoring techniques complement geodetic monitoring techniques.

Smoothed particle hydrodynamics (SPH) is a meshless method gaining popularity recently in geotechnical modeling. It is suitable to solve problems involving large deformation, free-surface, cracking and fragmentation. To promote the research and application of SPH in geotechnical engineering, we present LOQUAT, an open-source three-dimensional GPU accelerated SPH solver. LOQUAT employs the standard SPH formulations for solids with two geomechnical constitutive models which are the Drucker–Prager model and a hypoplastic model. Three stabilization techniques, namely, artificial viscosity, artificial pressure and stress regularization are included. A generalized boundary particle method is presented to model static and moving boundaries with arbitrary geometry. LOQUAT employs GPU acceleration technique to greatly increase the computational efficiency. Numerical examples show that the solver is convergent, stable and highly efficient. With a mainstream GPU, it can simulate large scale problems with tens of millions of particles, and easily performs more than one thousand times faster than serial CPU code.

A detailed exploration about the development of the microscopic behavior of red-bed mudstones and exploration of their anisotropic deformation mechanisms in-depth can help to optimize the improvement of red-bed subgrade. To discuss the effects of single immersion and dynamic wetting-drying cycles, the Aramis system was used to monitor the mudstone deformation, whose results were compared with results of conventional deformation tests; the patterns of moisture migration was analyzed. Variations in mineral compositions, particle orientation and pore characteristics during cycles were investigated. The results show that after encountering water, red-bed mudstones swelled in axial and shrank in radial; the swelling first started around the initial fissures. During wetting-drying cycles, the decrease of equivalent montmorillonite content leads to the weakening of water absorption capacity and deformation capacity of the red-bed mudstone from the sixth wetting-drying cycle; moisture migration causes a directional shift of mudstone particles towards the direction of moisture migration, which triggers anisotropy of the red-bed mudstone deformation; moreover, wetting-drying cycles lead to the increase of pores and fissures inside the red-bed mudstone, with a more complex morphology and the increase of scattered detrital particles, which are the main reasons for the continuous deformation of the red-bed mudstone.

In this study, a simple PFEM approach for analyzing large deformation problems in geotechnical practice is implemented in the commercial FEM package Abaqus. The main feature of the proposed Abaqus-PFEM approach lies in its capability to absorb the advantages of the functionality available in Abaqus and integrate them into PFEM with a single Python script, which leads to a considerable reduction in coding work. By utilizing the built-in functions in Abaqus to fulfil the standard incremental FEM analysis, as well as the powerful mesh-to-mesh solution mapping technique, the proposed Abaqus-PFEM approach allows for the large deformation analysis automatically running with a single Python script and requires no intervention from the user. The accuracy of the proposed Abaqus-PFEM approach is firstly validated through a simple elastic cantilever beam bending problem. Then, the performance and robustness of the proposed Abaqus-PFEM approach are further examined by three illustrative numerical examples: penetration of rigid footing, penetration of T-bar and pipeline–soil interaction problem. The numerical results demonstrate that the proposed Abaqus-PFEM approach as a powerful and easily extensible numerical tool is capable of handling large deformation and soil–structure interaction problems in geotechnical engineering, and consequently, it offers an alternative way to tackle such problems.

In the context of COVID-19 rampant worldwide since 2019, the stock of disposable single-use face masks (SUFMs) has climbed steadily, which results in an urgent worldwide environmental problem. This study aims to propose a potential method for processing and utilizing SUFMs in soil reinforcement to address the significant volume of discarded masks, thereby contributing to geotechnical engineering construction. Hence, in this study, SUFMs were prepared into three geosynthetic forms considered potential candidate options: fibers, geotextiles, and geocells. The performance of geosynthetics-reinforced sand was assessed by the static triaxial tests by considering the fibers reinforcement with the content of 0.25% and 1.0%, single-layer and three-layer geotextiles reinforcement, and geocells reinforcement. A series of numerical simulations were also conducted to investigate the failure mechanisms of various reinforced forms. The experimental results show that the three geosynthetic types can improve the sandy soil's shear strength and apparent cohesion. The SUFMs fibers reduce the elastic modulus due to the higher compressibility of the SUFMs, while the elastic modulus of geotextile and geocell-reinforced soil samples is elevated. The numerical analysis results indicate that the SUFMs fibers and geotextiles can limit the lateral deformation and spread the shear stress over a wider area through the interface friction between geosynthetics and soil. On the other hand, the vertical walls of geocells can provide direct lateral restraint, and the reinforcement effect is more direct and better.

Large squeezing deformation has always been a critical concern in the construction of deep-buried tunnels in soft-weak rock masses. This paper describes a case study on the large deformation mechanism and supporting method of the Maoxian tunnel in Sichuan Province, China, which is located in the core area influenced by the 2008 Wenchuan earthquake and suffered severe large deformation in broken phyllite under high geo-stress. Through a survey on the geological features, the deformation mechanism of surrounding rock and the failure characteristics of supporting structures of the Maoxian tunnel in F1 fault zone were studied. It was found that the occurrence of large deformation was due to the combined action of the high geo-stress and poor self-stability of carbonaceous phyllite. In order to control the squeezing deformation, single and double primary support methods were adopted in succession. A comparative field test was conducted to study their supporting mechanism and mechanical behavior in terms of surrounding rock pressure, internal stress of the steel arch, and axial force and bending moment of the secondary lining. The results revealed that the single primary support method cannot ensure the long-term safety of the tunnel, since many cracks in concrete occurred after about 180 days. The double primary support method, however, was able to control the large deformation and rheological effects of broken phyllite under high geo-stress effectively.

Multi-field information monitoring is useful to better understand the deformation and failure behaviour of landslides. Therefore, in this study, a physical slope model under excavation was analysed through multi-field monitoring to ascertain the failure mechanism of the slope. During the process of physical model tests, ① area information including 2D surface displacement, 2D surface strain, velocity, 2D surface temperature, and 3D surface deformation, ② line information including deep displacement and deep strain, and ③ point information of the earth pressure of the model were acquired via multi-field monitoring. The pre-failure, failure, and post-failure stages of the slope model are analysed through multi-field monitoring. The results indicate that the relative displacement between the yielding and stationary parts and a triangular shear plane reflect the deformation behaviour of the slope related to the arching effect. The arch ring expands and becomes elongated during the excavation process. The slope failure time can be effectively predicted via the inverse velocity method. Multi-field monitoring can reveal the behaviour of the slope model from different perspectives and offer new insights into the failure mechanism of the slope.

The issue of large deformation mechanism in soft rock tunnels has puzzled tunnel scholars for decades. Previous studies have not evolved a clear and common understanding. Therefore, detailed on-site measurement, full investigation and statistical analysis have been conducted on the instability and failure of Muzhailing Tunnel since its construction, whose length is beyond 15 km. The study aims at systematically analyzing the failure mechanisms and modes of Muzhailing Tunnel in monoclinic and soft-hard interbedded rock strata. Study results show that the angle between strata strike and tunnel axis greatly determines the magnitude of deformation, the dip direction significantly controls the bias direction and maximum deformation direction, and the dip angle deeply affects the deformation form. The failure modes of surrounding rock mainly include four types: spalling and overturning failure, bending failure, shear slip failure and buckling failure. Large deformation characteristics are summarized from six aspects: failure form, groundwater, sensitivity to influencing factors, deformation degree, deformation speed and deformation duration. The instability modes of primary lining include in-plane (transverse) instability and out-plane (longitudinal) instability. Finally, the causes of large deformation are analyzed from geological, structural, engineering and human factors.