scholarly journals Experiment and Analysis of Submarine Landslide Model Caused by Elevated Pore Pressure

2019 ◽  
Vol 7 (5) ◽  
pp. 146 ◽  
Author(s):  
Tao Liu ◽  
Yueyue Lu ◽  
Lei Zhou ◽  
Xiuqing Yang ◽  
Lei Guo
Keyword(s):  
Pore Pressure ◽  
Soil Layer ◽  
Initial Crack ◽  
Excess Pore Pressure ◽  
Deep Soil ◽  
Hydrate Decomposition ◽  
Dynamic Relationship ◽  
Geological Conditions ◽  
Shear Slip ◽  
Excess Pore

Hydrate decomposition is an important potential cause of marine geological disasters. It is of great significance to understand the dynamic relationship between hydrate reservoir system and the overlying seabed damage caused by its decomposition. The purpose of this study is to understand the instability and destruction mechanisms of a hydrated seabed using physical simulations and to discuss the effects of different geological conditions on seabed stability. By applying pressurized gas to the low permeability silt layer, the excess pore pressure caused by the decomposition of hydrate is simulated and the physical appearance process of the overlying seabed damage is monitored. According to the test results, two conclusions were drawn in this study: (1) Under the action of excess pore pressure caused by hydrate decomposition, typical phenomena of overlying seabed damage include pockmark deformation and shear–slip failure. In shallower or steeper strata, shear-slip failure occurs in the slope. The existence of initial crack in the stratum is the main trigger cause. In thicker formations or gentler slopes, the surface of the seabed has a collapse deformation feature. The occurrence of cracks in the deep soil layer is the main failure mechanism. (2) It was determined that the thickness and slope of the seabed, among other factors, affect the type and extent of seabed damage.

HHT Analysis on Pore Pressure Dissipation of Wave-Induced Fluidization in a Sandy Bed

2011 ◽  
Author(s):  
Shiaw-Yih Tzang ◽  
Yung-Lung Chen ◽  
Shan-Hwei Ou
Keyword(s):  
Pore Pressure ◽  
Soil Layer ◽  
Excess Pore Pressure ◽  
Pressure Measurements ◽  
Flume Tests ◽  
Dissipation Mechanism ◽  
Frequency Components ◽  
Excess Pore Pressures ◽  
Wave Induced ◽  
Excess Pore

Wave-induced pore pressure variations during the stage of increasing excess pore pressure consist of the mechanism of generation of fluidization. Moreover, in post-fluidization stage, pore pressure variations not only reveal the dissipation mechanism of fluidization but also the wave-fluidized bed interactions. Past results from a series of lab flume tests have further illustrated that pore pressure variations in a fluidized response are nonlinear and nonsataionary. Hence, the HHT method was further applied to analyze the pore pressure measurements in this study. The results demonstrate that after the dissipation of excess pore pressures the amplitudes of fundamental and higher-frequency components begin to decay. Meanwhile, the amplified amplitudes of fundamental and higher-frequency components during fluidization response would decrease with decreasing thickness of fluidized soil-layer in consecutive tests.

scholarly journals Effect of Deep Mixing Grid Spacing On The Settlement of Liquefied Soil, Using Numerical Approach

2022 ◽  
Author(s):  
Fereshteh Rahmani ◽  
Seyed Mahdi Hosseini
Keyword(s):  
Pore Pressure ◽  
Ground Improvement ◽  
Pressure Ratio ◽  
Soil Layer ◽  
Excess Pore Pressure ◽  
Analysis Model ◽  
Liquefaction Mitigation ◽  
Deep Mixing ◽  
Liquefiable Soil ◽  
Excess Pore

Abstract Liquefaction occurs in a loose and saturated sand layer, induces quite large damages to infrastructures, the importance of liquefaction mitigation has been emphasized to minimize earthquake disasters for many years. Many kinds of ground improvement techniques based on various improvement principles have been developed for liquefaction mitigation. Among them, deep mixing method with grid pattern was developed for liquefaction mitigation in the 1990s, where the grid of stabilized column walls functions to restrict the generation of excess pore pressure by confining the soil particle movement during earthquake. In this study, a parametric study of the grid-form deep mixing wall is performed using numerical modeling with GID+OpenSees interface V2.6.0. The finite element method with a three-dimensional analysis model can be used to estimate the foundation settlement over liquefiable soil layer. The validity of the developed model was evaluated by comparing the results obtained from the model with the results of numerical studies and the experimental centrifuge test to investigate the effect of deep mixing grid wall on the settlement and generation of excess pore pressure ratio of liquefiable soil. Based on the analysis, the settlement for improved soil was 69% smaller than the settlement for unimproved soil. The results also indicated that the grid wall space, relative density, and stiffness ratio between soil-cement columns and enclosed soil plays an important role in the occurrence of liquefaction and volumetric strains.

Excess Pore Pressure Dissipation Characteristics of Different Soil by CPTU on Pearl River Delta

2011 ◽  
Vol 71-78 ◽  
pp. 4606-4609
Author(s):  
Yan Chun Tang ◽  
Gao Tou Meng
Keyword(s):  
Pore Pressure ◽  
Pearl River Delta ◽  
Clay Soil ◽  
Soil Layer ◽  
River Delta ◽  
Excess Pore Pressure ◽  
Pearl River ◽  
Silty Clay ◽  
Sand Soil ◽  
Excess Pore

Through a lot of CPTU excess pore pressure dissipation tests on Pearl River Delta in China, excess pore pressure dissipation characteristics of different soil layer on Guangzhou-Zhuhai section of Beijing-Zhuhai Expressway and Taishan section of Guangdong West Coast Expressway has been analyzed. The dissipation time of 50% dissipation degree t50 of excess pore pressure dissipation curve by CPTU can be used as the auxiliary method to determine the type of soil, and through CPTU excess pore pressure dissipation tests, the t50 value of sand soil, silt, silty clay, clay soil and silt soil has been obtained; through comparison with the t50 value of different soil, the difference of sand soil, silt and clay soil can be roughly distinguished; the obvious boundary value between the t50 value of clay soil, silty clay and silt soil is not existed, so the t50 value can not be direct to determine the type of these clay type of soil. The achieved results can provide a research foundation for CPTU application research on Pearl River Delta in China.

Consolidation of a soil layer subsequent to cessation of deposition

2005 ◽  
Vol 42 (2) ◽  
pp. 678-682
Author(s):  
Guofu Zhu ◽  
Jian-Hua Yin
Keyword(s):  
Pore Pressure ◽  
Soil Layer ◽  
Average Degree ◽  
Excess Pore Pressure ◽  
Triangular Distribution ◽  
Pressure Distributions ◽  
Pore Pressures ◽  
Degree Of Consolidation ◽  
Excess Pore Pressures ◽  
Excess Pore

It is necessary in certain cases to estimate the progress of consolidation in a soil layer that has ceased increasing in thickness over time. In this paper, the existing excess pore pressures for two time–thickness relations are used as the "initial" pore pressures for analysing the consolidation of soil subsequent to the cessation of deposition. Average degrees of consolidation of the soil layer are presented for one-way drainage and two-way drainage boundary conditions. The average degrees of consolidation are compared with those for uniform and triangular initial excess pore pressure distributions. It is found that the average degree of consolidation for one-way drainage boundaries can be estimated using the value for the triangular distribution. The average degree of consolidation for two-way drainage boundaries is bound by the averages for both the uniform and the triangular initial excess pore pressure distributions.Key words: consolidation, deposition, drainage, settlement, soil.

Vibro-Stone Column Reinforcement Mechanism and Numerical Analysis

2012 ◽  
Vol 446-449 ◽  
pp. 1940-1943
Author(s):  
Yang Liu ◽  
Hong Xiang Yan
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Pore Pressure ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Excess Pore Pressure ◽  
Stone Column ◽  
Reinforcement Mechanism ◽  
Consolidation Theory ◽  
Excess Pore

Numerical simulation of vibro-stone column is taken to simulate the installation of vibro-stone column. A relationship based on test is adopted to calculate the excess pore pressure induced by vibratory energy during the installation of vibro-stone column. A numerical procedure is developed based on the formula and Terzaghi-Renduric consolidation theory. Finally numerical results of composite stone column are compared single stone column.

scholarly journals How deep does sand deposits in the Alentejo basin (Gulf of Cadiz) reach? Evaluating slope stability from bottom-current activities through time

2020 ◽  
Author(s):  
Davide Mencaroni ◽  
Roger Urgeles ◽  
Jonathan Ford ◽  
Jaume Llopart ◽  
Cristina Sànchez Serra ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Sediment Supply ◽  
Excess Pore Pressure ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Strait Of Gibraltar ◽  
Gulf Of Cádiz ◽  
The Stability ◽  
Iberian Margin ◽  
Excess Pore

<p>Contourite deposits are generated by the interplay between deepwater bottom-currents, sediment supply and seafloor topography. The Gulf of Cadiz, in the Southwest Iberian margin, is a famous example of extensive contourite deposition driven by the Mediterranean Outflow Water (MOW), which exits the Strait of Gibraltar, flows northward following the coastline and distributes the sediments coming from the Guadalquivir and Guadiana rivers. The MOW and related contourite deposits affect the stability of the SW Iberian margin in several ways: on one hand it increases the sedimentation rate, favoring the development of excess pore pressure, while on the other hand, by depositing sand it allows pore water pressure to dissipate, potentially increasing the stability of the slope.</p><p>In the Gulf of Cadiz, grain size distribution of contourite deposits is influenced by the seafloor morphology, which splits the MOW in different branches, and by the alternation of glacial and interglacial periods that affected the MOW hydrodynamic regimes. Fine clay packages alternates with clean sand formations according to the capacity of transport of the bottom-current in a specific area. Generally speaking, coarser deposits are found in the areas of higher MOW flow energy, such as in the shallower part of the slope or in the area closer to the Strait of Gibraltar, while at higher water depths the sedimentation shifts to progressively finer grain sizes as the MOW gets weaker. Previous works show that at present-day the MOW flows at a maximum depth of 1400 m, while during glacial periods the bottom-current could have reached higher depths.</p><p>In this study we derived the different maximum depths at which the MOW flowed by analyzing the distribution of sands at different depths along the Alentejo basin slope, in the Northern sector of the Gulf of Cadiz.</p><p>Here we show how changes in sand distribution along slope, within the stratigraphic units deposited between the Neogene and the present day, are driven by glacial – interglacial period alternation that influenced the hydrodynamic regime of the MOW.</p><p>By deriving the depositional history of sand in the Alentejo basin, we are able to correlate directly the influence that climatic cycles had on the MOW activity. Furthermore, by interpreting new multi-channel seismic profiles we have been able to derive a detailed facies characterization of the uppermost part of the Gulf of Cadiz.</p><p>An accurate definition of sand distribution along slope plays an important role in evaluating the stability of the slope itself, e.g. to understand if the sediments may be subjected to excess pore pressure generation. As sand distribution is a direct function of the bottom-current transport capacity, the ultimate goal of this study is to understand how climate variations can affect the stability of submarine slope by depositing contourite-related sand.</p>

Sign in / Sign up

Export Citation Format

Share Document