scholarly journals Comparative Study on Seismic Response of Pile Group Foundation in Coral Sand and Fujian Sand

2020 ◽  
Vol 8 (3) ◽  
pp. 189 ◽  
Author(s):  
Qi Wu ◽  
Xuanming Ding ◽  
Yanling Zhang ◽  
Zhixiong Chen
Keyword(s):  
Dynamic Response ◽  
Pore Pressure ◽  
Pressure Ratio ◽  
Physical And Mechanical Properties ◽  
Bending Moment ◽  
Horizontal Displacement ◽  
Shaking Table ◽  
Excess Pore Pressure ◽  
Coral Sand ◽  
Excess Pore

The physical and mechanical properties of coral sand are quite different from those of common terrestrial sands due to the special marine biogenesis. Shaking table tests of three-story structures with nine-pile foundation in coral sand and Fujian sand were carried out in order to study the dynamic response characteristics of pile-soil-structure system in coral sand under earthquake. The influence of shaking intensity on the dynamic response of the system was taken into consideration. The results indicated that the peak value of the excess pore pressure ratio of coral sand was smaller than that of Fujian sand under two kinds of shaking intensities; moreover, the development speed of excess pore pressure ratio of coral sand was smaller than that of Fujian sand. The liquefaction of coral sand was more difficult than Fujian sand under the same relative density and similar grain-size distribution. The horizontal displacement, settlement, column bending moment, and pile bending moment of coral sand were smaller than those of Fujian sand, respectively. The magnification effect of column bending moment of buildings in coral sand was less than that in Fujian sand with increasing shaking intensity. This study can provide some supports for the seismic design of coral reef projects.

scholarly journals A semi-empirical model to predict excess pore pressure generation in partially saturated sand

2020 ◽  
Vol 195 ◽  
pp. 02026
Author(s):  
Mousavi Sayedmasoud ◽  
Majid Ghayoomi
Keyword(s):  
Pore Pressure ◽  
Empirical Model ◽  
Pressure Ratio ◽  
Pore Fluid ◽  
Excess Pore Pressure ◽  
Saturated Soils ◽  
Partial Saturation ◽  
Liquefaction Resistance ◽  
Semi Empirical ◽  
Excess Pore

Past studies revealed that excess pore pressure generation due to cyclic loading is highly governed by induced strains, volumetric deformation potential of soil, number of cycles, and bulk stiffness of pore fluid. It is well established that partial saturation can significantly reduce bulk stiffness of pore fluid and consequently excess pore pressure generation during seismic loading. On the basis of that, a number of researchers have investigated induced partial saturation as an effective soil improvement technique to increase the liquefaction resistance of fully saturated soils. This paper focuses on development of a semi- empirical model to interpret the effects of partial saturation on the excess pore pressure generation in sands. In this regard, an existing strain based excess pore pressure ratio (ru) prediction model originally developed for fully saturated soils was modified to incorporate the effect of partial saturation on the excess pore pressure generation. The literature data as well as data from a series of strain-controlled direct simple shear test were used to evaluate the reliability of the proposed equation in predicting the excess pore pressure ratio in partial saturation condition.

Liquefaction potential of silts from CPTu

2007 ◽  
Vol 44 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Dawn A Shuttle ◽  
John Cunning
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Earthquake Engineering ◽  
Critical State ◽  
Pressure Ratio ◽  
Excess Pore Pressure ◽  
Liquefaction Potential ◽  
Triaxial Cell ◽  
Excess Pore

Silt tailings (slimes) are difficult materials to test in that, like sands, it is extremely difficult to obtain undisturbed samples and subsequently re-establish them in a triaxial cell for element testing in a laboratory in anything approaching their in situ condition. Evaluation of silt tailing behaviour has to depend on in situ tests, and the piezocone (CPTu) in particular. However, CPTs in silt generate substantial excess pore pressure and there is no established methodology to evaluate the measured responses in terms of soil properties, as drained sand-based CPT interpretation is inapplicable. A case history of particularly loose silt tailings is reported in which the National Center for Earthquake Engineering Research (NCEER) liquefaction assessment method would lead to uncertainty in the liquefaction potential. However, the extremely high CPTu excess pore pressure ratio, Bq, and low dimensionless CPT resistance, Qp, at this site indicates liquefaction is likely occurring during pushing of the CPT. Detailed finite element simulations of the CPT using a critical state model provided an effective stress framework to evaluate the in situ state parameter of the silt from the measured CPT data. This framework shows that the group of dimensionless CPT variables Q(1 – Bq) + 1 is fundamental for the evaluation of undrained response during CPT sounding. And, despite the high silt content, the interpretation indicates that the tailings are indeed liquefiable.Key words: liquefaction, CPT, silt, finite element, critical state.

Free Field Sediment Mobility on Australia’s North West Shelf

2013 ◽  
Author(s):  
Henning Mohr ◽  
Scott Draper ◽  
David White
Keyword(s):  
Sediment Transport ◽  
Pore Pressure ◽  
Best Practice ◽  
Free Field ◽  
Shaking Table ◽  
Excess Pore Pressure ◽  
Threshold Velocity ◽  
North West ◽  
Sediment Mobility ◽  
Excess Pore

Under cyclonic conditions, sediment on the North West Shelf (NWS) of Australia may become mobile in shallow water due to classical sediment transport or local liquefaction, and this can affect, for example, the on-bottom stability of subsea pipelines. In this paper, three calcareous sediments sampled from the NWS are analysed, together with realistic metocean data, to illustrate this potential for sediment mobility on the NWS. Specifically, experiments are performed in a recirculating flume (known as an O-Tube) to measure the erosional behaviour and an additional series of experiments are performed using a shaking table, on which each of the sediments have been liquefied and excess pore pressure measurements recorded to back calculate the consolidation coefficient. Soil characterisation data, threshold velocity measurements and shaking table results have then combined to illustrate the potential for sediment mobility for each of the NWS sediments. Best practice models are used to calculate wave and current combined shear stress at the seabed and excess pore pressure accumulation. We find that for these sediments, freshly deposited in laboratory samples, mobility due to sediment transport or liquefaction is very likely in cyclonic conditions on the NWS. Liquefaction is most likely for loosely packed silt, whilst sediment transport is most likely for sand. However, we also show that in more extreme cyclonic conditions there are a subset of sediments that can become mobile due to both sediment transport and liquefaction.

scholarly journals The Use of Ground Motion Parameters to identify the Liquefaction during a Strong Earthquake in Northern Thailand

2021 ◽  
Vol 27 (1) ◽  
pp. 1-8
Author(s):  
Lindung Zalbuin Mase
Keyword(s):  
Pore Pressure ◽  
Amplification Factor ◽  
Pressure Ratio ◽  
Excess Pore Pressure ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Northern Thailand ◽  
Motion Parameters ◽  
Excess Pore

This paper presents a ground response analysis to simulate the liquefaction phenomenon during the 2011 Tarlay Earthquake in northern Thailand. The site investigation data and geophysical measurements on 7 sites in northern Thailand were collected. The multi-springs element model was implemented in finite element ground response analysis. Several parameters, such as peak ground acceleration, peak ground velocity, amplification factor, excess pore pressure ratio, were observed. Furthermore, the correlation from the ground motion parameters was generated to estimate liquefaction potential, which was represented by excess pore pressure ratio. The result showed that the excess pore pressure ratio was relatively well correlated with several ground parameters, such as amplification factor, velocity-acceleration ratio, and factor of safety against liquefaction. The results could be also used for the engineering practice in predicting liquefaction potential in Northern Thailand.

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.

Pore Pressure Generation and Dissipation Effects on Spudcan Fixity in Normally Consolidated Clay

2013 ◽  
Author(s):  
Yu Yang ◽  
Fook Hou Lee ◽  
Siang Huat Goh ◽  
Jer-Fang Wu ◽  
Xi Ying Zhang
Keyword(s):  
Pore Pressure ◽  
Bending Moment ◽  
Soil Surface ◽  
Experimental Tests ◽  
Combined Loading ◽  
Degree Of Saturation ◽  
Excess Pore Pressure ◽  
Model Foundation ◽  
Small Rotation ◽  
Excess Pore

Spudcan rotational fixity under combined vertical, horizontal and moment loading is often assumed to be invariant with time. In reality, the actual rotational fixity of spudcan footing is likely to change with time as excess pore pressure builds up and dissipates. This paper describes a series of centrifuge experimental tests conducted at 100-g acceleration using a small spudcan model and specimens of normally consolidated reconstituted kaolin clay. Using a servo-motor, belt-driven actuator system, loading episodes comprising one thousand cycles of combined loading were applied to model foundation. The PPTs are installed in soil specimens to measure the excess pore pressure and degree of saturation of soil. One small-rotation test is conducted just after spudcan’s penetration; while another one small-rotation is conducted when the excess pore pressure is fully dissipated after the spudcan’s penetration. The results show bending moments at four locations along the spudcan shaft, which indicates that the lattice confers a significant lateral soil resistance, and the presence of the lattice will also cause the location of maximum bending moment to be up-shifted along the leg, towards to the soil surface. The rotational fixity of the spudcan shows distinct changes over time, which is attributed to consolidation and settlement effects. Comparison of fixity of spudcan with and without lattice leg indicates that the lattice leg can lead to a large increase in lateral resistance of deeply penetrated spudcans. This lattice leg effect has been largely ignored in both academic study and industrial design.

scholarly journals Physical Modeling of the Stability of a Revetment Breakwater Built on Reclaimed Coral Calcareous Sand Foundation in the South China Sea—Regular Wave

2021 ◽  
Vol 11 (5) ◽  
pp. 2325
Author(s):  
Kunpeng He ◽  
Jianhong Ye
Keyword(s):  
South China Sea ◽  
Pore Pressure ◽  
South China ◽  
The South China Sea ◽  
Excess Pore Pressure ◽  
Regular Wave ◽  
The South ◽  
Coral Sand ◽  
The Stability ◽  
Excess Pore

In the past several years, a series of artificial islands have been constructed on the top of coral reefs by China in the South China Sea by way of reclamation. A large number of revetment breakwater also has been built along the margin of these artificial islands. The stability of these revetment breakwater is the precondition for the normal service performance of these reclaimed coral sand islands. In this study, taking the reclamation engineering in the South China Sea as the background, a series of wave flume physical model tests (geometrical similarity scale is set to 1:10) are performed to investigate the dynamics and the stability of the revetment breakwater and its reclaimed coral sand foundation under the impact of regular wave. Experimental results show that the revetment breakwater has a maximum final settlement of 6 mm if built on loose coral sand foundation. Furthermore, there is indeed excess pore pressure generated in the reclaimed coral foundation with a maximum magnitude of 1.5 kPa. It is found that the excess pore pressure has not caused liquefaction in the coral sand foundation due to the fact that the accumulation of excess pore pressure only occurred in the first 10 cycles of wave loading. Finally, it is concluded that the revetment breakwater and its reclaimed coral sand foundation basically are stable under regular wave impacting. However, excessive water overtopping would be a potential threat for the vegetation behind the breakwater, as well as for the desalinated underground water of the reclaimed lands.

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.

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