Ground disturbance and deformation caused by a controlled gas release prior to engineering construction are commonly encountered geotechnical and geoenvironmental problems in shallow gas geology areas. In this work, typical characteristics of shallow gas geology and gas-charged sand in the Hangzhou Bay of China are analyzed. It is found that the occurrence configuration feature of sand in the shallow gas enrichment zone of reservoirs is similar to that of the common unsaturated soil, but its pore gas pressure is several times larger than the atmospheric pressure. The effect of the suction history on the deformation characteristics of sand is investigated by triaxial simulation tests using the Global Digital System (GDS). The deformation of reservoir sand caused solely by the suction reduction in the process of gas release is negligible, and the main deformation is attributed to the increasing net mean stress arising from the gas pressure reduction in the reservoir. Based on the findings from the triaxial tests, a simplified constitutive model for the gas-charged sand under the special stress path of gas release is developed to describe its deformation behaviors. Then, combined with the two-phase flow equation of incompatible fluid seepage, the proposed model is applied to the three-phase soil-water-gas–coupled analysis of a typical gas-bearing ground with a gas exhaust shaft. The numerical results match the field monitoring data well. Thus, the proposed method can be used to quantitatively evaluate the geoenvironmental effect of an engineered gas release on existing adjacent structures in shallow gas regions.

To simulate the effects of fines content on the liquefaction properties of sand, specimens of different fines content were prepared. Based on cyclic triaxial compression tests of these samples, the effects of fines content on the liquefaction properties were analyzed. Results show that for a constant value of dry density, the liquefaction resistance decreases with increasing fines content. Beyond the critical value of fines content of 30% the trend is reversed and the liquefaction resistance increases with increasing fines content. The results are consistent with the variation of relative density with increasing fines content, which verifies the effects of non-plastic fine-grained soils on liquefaction resistance of sandy soil reported by Polito et al. (2001).

In this study, for triaxial compression testing in geotechnical engineering, large-scale triaxial shear tests of coarse-grained soil were performed under end-restraint and end-free (microfriction) conditions utilizing a large-scale triaxial shear apparatus and a self-developed microfriction load-transfer plate. Under end-restraint and end-free (microfriction) circumstances, the strength and deformation characteristics of the coarse-grained soil were investigated. Further, the effect of the end restraint on the stress–strain characteristics of the coarse-grained soil was analyzed. The findings showed that the coarse-grained soil’s stress–strain curves under the end-restraint and end-free (microfriction) conditions displayed both softening under low confining pressures and hardening under high confining pressures. However, the stress–strain curves’ tendency to soften under low confining pressures was more pronounced under the end-free (microfriction) condition. Due to the influence of the end constraint, the peak strength of the coarse-grained soil increased under the same confining pressure, although the increase was less than 10% when the specimen had the typical height-to-diameter ratio of 2 in the drained triaxial test. Meanwhile, the coarse-grained soil first displayed volumetric contraction under the low confining pressures, followed by volumetric dilation, and it displayed volumetric dilation under the high confining pressures. The volumetric contraction tendency of the coarse-grained soil was more pronounced in the first stages of shearing when the low confining pressures were present. As the shear increased, it became more obvious that the coarse-grained soil had a tendency to dilate under the end-free (microfriction) conditions. Throughout the shearing operation, the coarse-grained soil exhibited a high propensity toward shear contraction. The coarse-grained soil’s strength values were not greatly impacted by the end limitation, but the deformation parameters were. Under the end-restraint conditions, the deformation parameter increased significantly, while the strength parameter only changed slightly.

With the Internet of Things (IoT) and communication technologies are snowballing, various applications (e.g., e-health and face recognition) are generated by IoT devices (IoTDs). Nevertheless, these IoTDs generally have constrained computation resources. By offloading the IoT applications to be processed by the MEC servers, mobile edge computing (MEC) is envisioned as a promising and effective solution to address this problem. Meanwhile, security is a critical issue for task offloading in MEC. While plenty of studies have focused on IoT tasks offloading, many of them ignored the security issue. Moreover, many previous works ignored the resource allocation of MEC servers. In addition, as dynamic voltage scaling (DVS) technology is flexible in the design of MEC systems, we integrate this technology with task offloading. In this paper, the problem of IoT applications offloading in an MEC system is studied, whose goal is to minimize computation overheads measured by the task processing delay and energy consumption of IoTDs. The AES cryptographic technique is adopted to make sure that the security of the data of the offloaded tasks is guaranteed. An optimization problem of security-aware task offloading is formulated and solved by proposing an efficient resource-allocation scheme. Experimental results are performed to evaluate and confirm the performance of the proposed security model.

The influence of saturation on the Poisson’s ratio v of reservoir sediments has an engineering significance in the field of oil and nature gas exploration. Based on a self-developed combined (BE-EE-RC) test system, under the dehydration path, the Poisson’s ratio variation of reservoir silty-fine sand in Hangzhou Bay, China, was investigated. Results show that the P- and S-wave velocities vary non-monotonically with decreasing saturation at different net stresses, and reach a maximum at the optimum saturation S_r(opt); Biot’s theory with respect to variation in V_p with S_r matches well with the measured e data. With a small amount of gas intrusion, Poisson’s ratio of saturated sand shows a sudden drop and gradually stabilizes; then, it attenuates slowly and reaches the minimum value at S_r(opt). Once the saturation degree decreases to the level lower than S_r(opt), it rapidly increases. Based on the soil–water characteristic curve (SWCC) and mesoscopic evolution of internal pore water morphology, the variation in Poisson’s ratio v can be divided into four segments of saturation: the boundary effect stage, the primary transition stage, the secondary transition stage, and the unsaturated residual stage. Ultimately, a prediction model for Poisson ratio’s v of the silty-fine sand was proposed to consider the saturation variation.