Liquefaction Mitigation Using Stone Columns Around Deep Foundations: Full-Scale Test Results

2000 ◽  
Vol 1736 (1) ◽  
pp. 110-118 ◽  
Author(s):  
Scott A. Ashford ◽  
Kyle M. Rollins ◽  
S. Case Bradford V ◽  
Thomas J. Weaver ◽  
Juan I. Baez
Keyword(s):  
Pore Pressure ◽  
Ground Improvement ◽  
Full Scale ◽  
Stone Columns ◽  
Excess Pore Pressure ◽  
Deep Foundations ◽  
Laterally Loaded Piles ◽  
Before And After ◽  
Laterally Loaded ◽  
Excess Pore

The results presented were developed as part of a larger project analyzing the behavior of full-scale laterally loaded piles in liquefied soil, the first full-scale testing of its kind. Presented here are the results of a series of full-scale tests performed on deep foundations in liquefiable sand, both before and after ground improvement, in which controlled blasting was used to liquefy the soil surrounding the foundations. Data were collected showing the behavior of laterally loaded piles before and after liquefaction. After the installation of stone columns, the tests were repeated. From the results of these tests, it can be concluded that the installation of stone columns can significantly increase the density of the improved ground as indicated by the cone penetration test. Furthermore, it was found that the stone column installation limited the excess pore pressure increase from the controlled blasting and substantially increased the rate of excess pore pressure dissipation. Finally, the stone columns were found to significantly increase the stiffness of the foundation system by more than 2.5 to 3.5 times that in the liquefied soil. This study provides some of the first full-scale quantitative results on the improvement of foundation performance due to stone columns in a liquefiable deposit.

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.

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>

scholarly journals Consolidated and Undrained Ring Shear Tests on the Sliding Surface of the Hsien-du-shan Landslide in Taiwan

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Hung-Ming Lin ◽  
Jian-Hong Wu ◽  
Erik Sunarya
Keyword(s):  
Pore Pressure ◽  
Rock Avalanche ◽  
Excess Pore Pressure ◽  
High Water Content ◽  
Sliding Surface ◽  
Shear Tests ◽  
Typhoon Morakot ◽  
Ring Shear ◽  
Ring Shear Tests ◽  
Excess Pore

A new consolidated undrained ring shear test capable of measuring the pore pressures is presented to investigate the initiation mechanism of the Hsien-du-shan rock avalanche, triggered by Typhoon Morakot, in southern Taiwan. The postpeak state of the landslide surface between the Tangenshan sandstone and the remolded landslide gouge is discussed to address the unstable geomorphological precursors observed before the landslide occurred. Experimental results show that the internal friction angle of the high water content sliding surface in the total stress state, between 25.3 and 26.1°, clarifies the reason of the stable slope prior to Typhoon Morakot. In addition, during the ring shear tests, it is observed that the excess pore pressure is generated by the shear contractions of the sliding surface. The remolded landslide gouge, sheared under the high normal stress, rendered results associated with high shear strength, small shear contraction, low hydraulic conductivity, and continuous excess pore pressure. The excess pore pressure feedback at the sliding surface may have accelerated the landslide.

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.

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