An Analytical Model and Its Application in Reliability Analysis of Formation Failure during Hydrate Production in Deep-sea Areas

Mingjing Jiang,Jiajia Huang,Huaning Wang 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.1

Methane hydrates (MHs) have potential economic and environmental significance. However, due to the sharp reduction in the mechanical properties of methane hydrate-bearing sediments (MHBS) caused by hydrate dissociation, the risk of formation failure in marine MHs exploitation is higher than that in conventional oil and gas exploitation. Formation failure in marine hydrate production probably leads to serious sand production or subsequent formation instability. A simplified and efficient analytical model is proposed at first for prediction of formation failure as well as the displacement around the wellbore during hydrate production, and then the reliability analysis for formation failure is performed by the Advanced First Order Second Moment Method based on the analytical solutions. This model considers the key factors affecting the formation failure, including 1) the partial coupling of multiple fields (the influence of pore pressure on mechanical field and the influence of hydrate dissociation on pore pressure, temperature and mechanical field), 2) the effect of gas/water or heat absorption caused by hydrate dissociation on pore pressure or temperature, 3) the change of mechanical properties of formation induced by hydrate dissociation and 4) the casing-formation interaction. The analytical solutions are verified and validated by numerical models. According to the analysis, the casing is sufficiently safe in the cross section due to its high stiffness, while the formation would be failure at the wellbore or dissociated front due to the stiffness/strength deterioration induced by hydrate dissociation. Hydrate dissociation leads to an increase in formation failure probability by approximately 20%. The probability of formation failure at the wellbore is about 30% higher than that at the dissociated front. The uncertainties in the internal friction angle and elastic modulus ratio have the greatest effect on formation failure probability.

FEM and Experimental Analysis of Lunar Soil Excavation Test

Mingjing Jiang,Banglu Xi,Zhenyu Guo,Huayang Lei 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8

A series of soil cutting tests was firstly carried out on the Earth on a ground composed of Tongji-1 lunar soil simulant (TJ-1 simulant) to experimentally investigate the effects of cutting depth, blade width, rake angle and blade arc angle on the excavation force. Then the tests were numerically simulated with the Finite Element Method (FEM), where a constant velocity was applied to the soil in contact with the blade, namely the soil cutting method or a rigid blade was generated and moved to cut the soil, namely the blade cutting method. The results show that the FEM simulation using the soil cutting method can provide excavation forces close to the experimental data when the rake angle is 0°, and well capture the effects of cutting depth, blade width and blade arc angle except the rake angle. The FEM simulation using the blade cutting method can capture the effect of rake angle while the predicted excavation forces are much larger than the experimental data. Nevertheless, both the methods cut the soil to a small displacement beyond which the analysis is unable to meet the convergence requirement.

A Strength Criterion for Deep Rock with Stochastic Fractures via DEM Simulations

Mingjing Jiang,Asen Liu,Huaning Wang,Guowen Lu,Lei Li 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

Criteria for rock strength mostly focus on macromechanical parameters, which cannot directly explain the relationship between microscopic fracture characteristics and strength. This paper analyses the strength characteristics of deep jointed rock with stochastic fractures by the distinct element method (DEM) and proposes a new strength criterion. First, an improved bond contact model and the smooth-joint contact model are implemented within the framework of DEM to simulate the characteristics of deep rock. Then, triaxial compression tests on Berea sandstone are also numerically simulated under various confining pressures and fracture intensities (P32). Finally, a strength criterion is proposed and validated based on thenumerical and experimental results. The criterion can capture the nonlinear relationshipbetween the major principal stress and the confining pressure and reveal the microscopic fracture characteristics of deep rock. However, the criterion does not consider the influence of the intermediate principal stress. The average deviation between all the predicted strengths and the experimental results is 5.12%, which demonstrates that the criterion has good applicability.

Metabolic reprogramming and epigenetic modifications in cancer: from the impacts and mechanisms to the treatment potential

Xu Xuemeng,Peng Qiu,Jiang Xianjie,Tan Shiming,Yang Yiqing,Yang Wenjuan,Han Yaqian,Chen Yuyu,Oyang Linda,Lin Jinguan,Xia Longzheng,Peng Mingjing,Wu Nayiyuan,Tang Yanyan,Li Jinyun,Liao Qianjin,Zhou Yuju 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-

Metabolic reprogramming and epigenetic modifications are hallmarks of cancer cells. In cancer cells, metabolic pathway activity varies during tumorigenesis and cancer progression, indicating regulated metabolic plasticity. Metabolic changes are often closely related to epigenetic changes, such as alterations in the expression or activity of epigenetically modified enzymes, which may exert a direct or an indirect influence on cellular metabolism. Therefore, exploring the mechanisms underlying epigenetic modifications regulating the reprogramming of tumor cell metabolism is important for further understanding tumor pathogenesis. Here, we mainly focus on the latest studies on epigenetic modifications related to cancer cell metabolism regulations, including changes in glucose, lipid and amino acid metabolism in the cancer context, and then emphasize the mechanisms related to tumor cell epigenetic modifications. Specifically, we discuss the role played by DNA methylation, chromatin remodeling, noncoding RNAs and histone lactylation in tumor growth and progression. Finally, we summarize the prospects of potential cancer therapeutic strategies based on metabolic reprogramming and epigenetic changes in tumor cells.

Dynamic Response of Lunar Soil Caused by Landing Impact

Ailan Che,Renjie Zhu,Mingjing Jiang 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.11

In recent years, there is an increasing interest on lunar exploration and future utilization of lunar resources. Technology of landing is a key in order to establish frequent access to the lunar surface. For a lunar lander, one of the major tasks is to accurately determine the loads and energy absorption capability during the landing event. On the other hands, it should be paid special attention on the study of wave propagation phenomenon in lunar soil and its dynamic response and dissipated energy by the lunar soil. A series of model tests for the simulated lunar soil model with plane and slope are conducted. The model tests are performed to study on the regularity of wave propagation and its attenuation in lunar soil. The waveform of acceleration, velocity and earth pressure in the model are observed. The research focuses on the analysis of the phenomenon through numerical methods. The wave propagation characteristics of the lunar soil model with plane and slope is assessed by means of dynamic FEM analyses in three dimensions. The analysis is obtained in the time domain and allows the consideration of multiple wave reflections between layers. It is concluded that the wave field propagation in lunar soil during landing impact mainly shows Rayleigh wave along axial of impact pads, and repeatedly superimposing occur between impact pads. The predominant frequency of the landing impact is over 100 Hz. The response is quickly attenuated in lunar soil and its propagation distance is very limited. Moreover, according to the numerical results and the model test results, it can be found that a small input wave velocity (< 1 m/s) has a great impact on the maximum acceleration and displacement. Furthermore, when it reaches a certain value, the maximum acceleration and displacement reach the maximum value. The plastic strain zone increases rapidly with the increasing input wave peak velocity, when the plastic strain is > 0.05, and when input wave velocity is 4 m/s, the ground floor of the landing pad is in plastic.

Analytical Solution to the Seepage Field of Two Parallel Noncircular Tunnels in Permeable Anisotropic Ground

Fengran Wei,Huaning Wang,Guangshang Zeng,Mingjing Jiang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.12

This paper provides an analytical solution and solving procedure for the seepage field around two noncircular tunnels in anisotropic permeable ground. The anisotropic problem is first made equivalent to an isotropic problem by coordinate transformation. Then, by using Schwartz alternate method and conformal mapping, a precise analytical solution is obtained based on the anisotropic problem of single tunnel with redundant hydraulic heads at tunnel boundary. The noncircular tunnel interaction and the permeable anisotropy are considered accurately. The iterative procedure is simple and efficient in its calculations, and achieves good convergence. The results of the analytical model are compared with the finite element results, and show good agreement. Finally, some parametric studies are present to research the influences of tunnel shapes and the anisotropic permeability ratio on the seepage field, and the effect of the location of the pilot tunnel on the seepage field of the primary tunnel is also investigated.

Experimental Study on the Entropy Change Failure Precursors of Marble under Different Stress Paths

Erdi Abi,Hechuan Yuan,Yu Cong,Zaiquan Wang,Mingjing Jiang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.1

In this paper, the indoor loading and unloading tests and acoustic emission (AE) monitoring tests of marble under different stress paths are carried out. Based on the AE events in the process of rock failure, this paper introduces the concept of information entropy of Shannon, and defines a new cumulative state information entropy which can characterize the degree of disorder and accumulation of rock microcracks. This paper also offers a comparative analysis on the evolution law of rock entropy under different paths and different loading and unloading conditions. The results show that the newly defined cumulative state information entropy can well reflect the order change of the loading and unloading process system, and there are significant differences in entropy evolution under different stress paths, but the entropy generally evolves with the development of the system from “quasi-equilibrium” to “far away from equilibrium”. The higher the unloading level is, the greater the confining pressure is, the stronger the unloading disturbance is, and the entropy value drops sharply at the starting point of unloading. The faster the unloading rate is, the later the rock fracture instability is, and the later the entropy drop point of the system appears. The change rate of entropy value |ΔH|= 0.1 can be used as the precursory signal threshold of rock confining pressure unloading disturbance damage and peak rupture instability.