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.

The Effects of Geosynthetic-Reinforcement on Consolidation Behavior of Soft Clay Embankment under Step Construction

2018 ◽  
Vol 783 ◽  
pp. 46-50
Author(s):  
Yu Cong Gao ◽  
Rong Chen ◽  
Dong Xue Hao ◽  
Myoung Soo Won
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Pore Pressure ◽  
Clay Soil ◽  
Clayey Soil ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Calculation Results ◽  
Consolidation Behavior ◽  
Excess Pore

Geosynthetics–reinforced structures are widely used in embankments and walls. This paper presents the simulation of the embankment under load in order to compare the behavior of clay embankment with and without wrapping-facing-geosynthetics-reinforcement using finite element method (FEM) and to analyse the variation of behavior included of displacement and excess pore pressure under the different over-consolidation ratios (OCR). The calculation results show that embankment with higher OCR showing lower displacement compare to embankment with lower OCR. However, OCR isn’t very sensitive to the dissipation of excess pore pressure. Geosynthetics-reinforcements could reduce the displacement of embankment and accelerate dissipation of excess pore pressure after construction and surcharge. Gravel, geosynthetics-reinforcement and clay soil are properly combined, clayey soil is expected to be useful as embankment material.

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 Wave-Induced Seafloor Instability in the Yellow River Delta: Flume Experiments

2019 ◽  
Vol 7 (10) ◽  
pp. 356 ◽  
Author(s):  
Wang ◽  
Zhu ◽  
Liu
Keyword(s):  
Pore Pressure ◽  
Yellow River ◽  
Wave Process ◽  
Yellow River Delta ◽  
Wave Action ◽  
River Delta ◽  
Excess Pore Pressure ◽  
The Yellow River ◽  
The Yellow River Delta ◽  
Excess Pore

Geological disasters of seabed instability are widely distributed in the Yellow River Delta, posing a serious threat to the safety of offshore oil platforms and submarine pipelines. Waves act as one of the main factors causing the frequent occurrence of instabilities in the region. In order to explore the soil failure mode and the law for pore pressure response of the subaqueous Yellow River Delta under wave actions, in-lab flume tank experiments were conducted in this paper. In the experiments, wave loads were applied with a duration of 1 hour each day for 7 consecutive days; pore water pressure data of the soil under wave action were acquired, and penetration strength data of the sediments were determined after wave action. The results showed that the fine-grained seabed presented an arc-shaped oscillation failure form under wave action. In addition, the sliding surface firstly became deeper and then shallower with the wave action. Interestingly, the distribution of pores substantially coincided with that of sliding surfaces. For the first time, gas holes were identified along with their positioning and angle with respect to the sediments. The presence of gas may serve as a primer for submarine slope failures. The wave process can lead to an increase in the excess pore pressure, while the anti-liquefaction capacity of the sediments was improved, causing a decrease in the excess pore pressure resulting from the next wave process. Without new depositional sediments, the existing surface sediments can form high-strength formation under wave actions. The test results may provide a reference for numerical simulations and engineering practice.

scholarly journals Surface deformation evolution in the Pearl River Delta between 2006 and 2011 derived from the ALOS1/PALSAR images

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Genger Li ◽  
Guangcai Feng ◽  
Zhiqiang Xiong ◽  
Qi Liu ◽  
Rongan Xie ◽  
...  
Keyword(s):  
Land Subsidence ◽  
Pearl River Delta ◽  
Surface Deformation ◽  
Soft Soil ◽  
Soil Layer ◽  
Intrinsic Factor ◽  
Surface Subsidence ◽  
River Delta ◽  
Pearl River ◽  
Human Interference

AbstractThis study monitors the land subsidence of the whole Pearl River Delta (PRD) (area: ~ 40,000 km2) in China using the ALOS1/PALSAR data (2006–2011) through the SBAS-InSAR method. We also analyze the relationship between the subsidence and the coastline change, river distribution, geological structure as well as the local terrain. The results show that (1) the land subsidence with the average velocity of 50 mm/year occurred in the low elevation area in the front part of the delta and the coastal area, and the area of the regions subsiding faster than 30 mm/year between 2006 and 2011 is larger than 122 km2; (2) the subsidence order and area estimated in this study are both much larger than that measured in previous studies; (3) the areas along rivers suffered from surface subsidence, due to the thick soft soil layer and frequent human interference; (4) the geological evolution is the intrinsic factor of the surface subsidence in the PRD, but human interference (reclamation, ground water extraction and urban construction) extends the subsiding area and increases the subsiding rate.

scholarly journals Surface Deformation Evolution in the Pearl River Delta between 2006 and 2011 derived from the ALOS1/PALSAR images

2020 ◽  
Author(s):  
Genger Li ◽  
Guangcai Feng ◽  
Zhiqiang Xiong ◽  
Qi Liu ◽  
Rongan Xie ◽  
...  
Keyword(s):  
Land Subsidence ◽  
Pearl River Delta ◽  
Surface Deformation ◽  
Soft Soil ◽  
Soil Layer ◽  
Intrinsic Factor ◽  
Surface Subsidence ◽  
River Delta ◽  
Pearl River ◽  
Human Interference

Abstract This study monitors the land subsidence of the whole Pearl River Delta (PRD) (area: ~40,000 km2) in China using the ALOS1/PALSAR data (2006-2011) through the SBAS-InSAR method. We also analyze the relationship between the subsidence and the coastline change, river distribution, geological structure as well as the local terrain. The results show that (1) the land subsidence with the average velocity of 50 mm/year occurred in the low elevation area in the front part of the delta and the coastal area, and the area of the regions subsiding fast than 30 mm/year between 2006 and 2011 is larger than 122 km2; (2) the subsidence order and area estimated in this study are both much larger than that measured in previous studies; (3) the areas along rivers suffered from surface subsidence, due to the thick soft soil layer and frequent human interference; (4) the geological evolution is the intrinsic factor of the surface subsidence in the PRD, but human interference (reclamation, ground water extraction and urban construction) extends the subsiding area and increases the subsiding rate.

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.

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.

Study on Variation Rule of Pore Pressure on CPTU Model Test

2010 ◽  
Vol 160-162 ◽  
pp. 544-549
Author(s):  
Yan Chun Tang ◽  
Gao Tou Meng
Keyword(s):  
Pore Pressure ◽  
Clay Soil ◽  
Excess Pore Pressure ◽  
Horizontal Distance ◽  
Penetration Test ◽  
Piezocone Penetration Test ◽  
Saturated Clay ◽  
Short Time ◽  
Variation Rule ◽  
Excess Pore

Through a series of Piezocone Penetration Test (CPTU) model tests with saturated clay soil, excess pore pressure produced by CPTU penetrating and dissipating has been measured by CPTU probe and pore pressure mini-transducers, the variation rules of excess pore pressure has been analyzed, the results show that at the same transducers layer, the value of initial excess pore pressure at the probe is biggest, and with the horizontal distance from probe increasing, the value of initial excess pore pressure measured by transducers around the probe has been decreased quickly; at the same dissipating process, the value of initial excess pore pressure measured by transducers locating in the same horizontal plane with probe is bigger than the value by transducers of the other layer; difference between the variation rule of excess pore pressure dissipation measured by CPTU probe and pore pressure mini-transducers is that after the value of excess pore pressure is maximum, with the dissipating time increasing, the value of excess pore pressure measured by probe decreased rapidly, but at first the value of excess pore pressure measured by transducers decreased slowly and then after a short time decreased rapidly; the time of 90% of the maximum of excess pore pressure dissipating measured by CPTU probe is longer than the time of 90% of the maximum of excess pore pressure dissipating measured by transducers; at the same transducers layer, with horizontal distance from the probe increasing, the time of 90% of the maximum of excess pore pressure dissipating decreased. The achieved result can provide a foundation for further study for CPTU mechanism.

Incremental transformation of a traditional village in China's Pearl River Delta

TERRITORIO ◽  
2015 ◽  
pp. 121-129 ◽  
Author(s):  
Peter Bosselmann ◽  
Francesca Frassoldati ◽  
Ping Su ◽  
Haohao Xu
Keyword(s):  
Pearl River Delta ◽  
River Delta ◽  
Pearl River
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