Hyperstatic reaction method for calculations of tunnels with horseshoe-shaped cross-section under the impact of earthquakes     

Chi  Thanh Nguyen  Alexandr  Gospodarikov 《地震工程与工程振动(英文版)》2020,19(1):179-188

Tunnels are now an integral part of the infrastructure in major cities around the world. For many reasons, these tunnels have horseshoe-shaped cross-sections with round top and flat bottom. This paper presents some improvements to the use of the Hyperstatic Reaction Method-HRM for analysing tunnels with horseshoe-shaped cross-sections when these tunnels operate under the influence of earthquakes, particularly in cases when the tunnel lining is a continuous lining. The analysis used parameters of a tunnel from the Hanoi metro system, as well as parameters of the strongest earthquake that may occur in the central Hanoi area in the improved HRM and 2 D numerical methods using the ABAQUS software. On the basis of the results obtained, the paper gives conclusions about the HRM methodology when it is used to calculate tunnels that have horseshoe cross-sections operating under the influence of earthquakes.  相似文献   

The construction of a simple portable electromagnetic vibrator from commercially available components     

Timothy Dean  Hoang Nguyen  Anton Kepic  David Halliday 《Geophysical Prospecting》2019,67(6):1686-1697

Since its introduction in the late 1950s, hydraulic vibrators have become the dominant source for land seismic surveys. The hydraulic vibrators typically used for commercial land seismic acquisition, however, are large, costly to operate and expensive to purchase. This inhibits their use for small-scale and short-duration surveys as well as Vibroseis research. In this paper we describe, in detail, the construction of a portable vibrator from commercially available components for a cost of less than $US2,000. Data shows that the vibrator is able to successfully transmit sweeps from 15 to 180 Hz with different spectral contents. The vibrator produces a stronger signal than a sledgehammer and we estimate its output to be around 1 kN. The frequency content of the data was concentrated at lower frequencies (<100 Hz) and the ground-roll was far more energetic than that produced using a sledgehammer.  相似文献   

Zeta potential of porous rocks in contact with mixtures of monovalent and divalent electrolytes     

Luong Duy Thanh  Rudolf Sprik  Xuan Ca Nguyen 《Geophysical Prospecting》2019,67(5):1354-1368

The zeta potential is one of the most important parameters influencing the electrokinetic coupling. Most reservoir rocks are saturated or partially saturated by natural water containing various types of ions (mostly monovalent and divalent ions). Therefore, understanding how the zeta potential behaves for mixtures of electrolytes is very important. In this work, measurements of the zeta potential for four different silica-based samples saturated by seven different mixtures of monovalent and divalent electrolytes are then carried out at a fixed ionic strength. It is seen that the magnitude of the measured zeta potential decreases with increasing divalent cation fraction. The experimental results are then explained by a model developed for mixtures of monovalent and divalent electrolytes. The result shows that the theoretical model is able to reproduce the main trend of the variation of the zeta potential with divalent cation fractions. Additionally, the model can fit the experimental data reported in literature well for reasonable values of the input parameters.  相似文献   

The impact of internal waves on upper continental slopes: insights from the Mozambican margin (southwest Indian Ocean)     

Elda Miramontes  Gwenael Jouet  Estelle Thereau  Miguel Bruno  Pierrick Penven  Charline Guerin  Pascal Le Roy  Laurence Droz  Stephan J. Jorry  F. Javier Hernández-Molina  Antoine Thiéblemont  Ricardo Silva Jacinto  Antonio Cattaneo 《地球表面变化过程与地形》2020,45(6):1469-1482

Evidences of sedimentation affected by oceanic circulation, such as nepheloid layers and contourites are often observed along continental slopes. However, the oceanographic processes controlling sedimentation along continental margins remain poorly understood. Multibeam bathymetry and high-resolution seismic reflection data revealed a contourite depositional system in the Mozambican upper continental slope composed of a contourite terrace (a surface with a gentle seaward slope dominated by erosion) and a plastered drift (a convex-shape sedimentary deposit). A continuous alongslope channel and a field of sand dunes (mainly migrating upslope), formed during Holocene, were identified in the contourite terrace at the present seafloor. Seismic reflection data of the water column show internal waves and boluses propagating in the pycnocline near the upper slope. The channel and the dunes are probably the result of the interaction of the observed internal waves with the seafloor under two different conditions. The alongslope channel is located in a zone where intense barotropic tidal currents may arrest internal solitary waves, generating a hydraulic jump and focused erosion. However, upslope migrating dunes may be formed by bottom currents induced by internal solitary waves of elevation propagating landwards in the pycnocline. These small-scale sedimentary features generated by internal waves are superimposed on large-scale contouritic deposits, such as plastered drifts and contourite terraces, which are related to geostrophic currents. These findings provide new insights into the oceanographic processes that control sedimentation along continental margins that will help interpretation of palaeoceanographic conditions from the sedimentary record. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Study the elastic properties and the anisotropy of rocks using different machine learning methods     

Tuan Nguyen-Sy  Quy-Dong To  Minh-Ngoc Vu  The-Duong Nguyen  Thoi-Trung Nguyen 《Geophysical Prospecting》2020,68(8):2557-2578

This paper aims to demonstrate that the elastic stiffnesses and the anisotropic parameters of rocks can be accurately predicted from geophysical features such as the porosity, the density, the compression stress, the pore pressure and the burial depth using relevant machine learning methods. It also suggests that the extreme gradient boosting method is the best method for this purpose. It is more accurate, extremely faster to train and more robust than the artificial neural networks and the support vector machine methods. Very high R-squared scores was obtained for the predicted elastic stiffnesses of a relevant dataset that is available in the literature. This dataset contains different types of rocks, and the values of the features are in large ranges. An optimal set of parameters was obtained by considering an appropriate sensitivity analysis. The optimized model is very easy to implement in Python for practical applications.  相似文献   

情理整合视角下旅游者环境责任行为与 意愿悖离研究——基于Logistic-ISM模型     

段正梁  彭振  杨左  鲍青  阮氏莲 《热带地理》2021,41(1):104-113

基于对岳麓山景区447位旅游者的实地调研,运用拓展的计划行为理论并结合Logistic回归模型,分析影响两者发生悖离的因素,并进一步利用ISM解释结构模型分析各因素之间的逻辑关系.从Logistic回归结果看,旅游者的行为态度、感知行为控制等相关理性认知越好,发生悖离的可能性越低;旅游者积极环境情感和消极环境情感对悖离...  相似文献   

The roles of the reversibility and irreversibility of capillary bonds on the impact dynamics of agglomerates     

Vo  Thanh-Trung  Nguyen  Trung-Kien 《Acta Geotechnica》2023,18(1):217-233

Acta Geotechnica - Wet agglomerates such as iron-ores, tablets, and aggregates are omnipresent in multi–field industries. However, our understanding of the impact dynamics of these materials...  相似文献