Liquefaction Of Saturated Sand Research Articles

Seismic behavior of irregular underground structures in saturated sand

Sand liquefaction is one of the leading causes of severe earthquake damage. In this study, shaking table tests were carried out to investigate the dynamic interaction between the saturated sand and the irregular subway stations. In this test, a method for the preparation of a liquefiable foundation based on a flexible sensing chain combined with water sedimentation was proposed. Typical test results were interpreted, including the development and spatial distribution of pore pressure, surface subsidence, acceleration, deformation, and dynamic earth pressure. Results show that the spatial distribution of excess pore water pressure is changed by the irregular underground structure, and the liquefiable soil below the bottom plate of the structure can be divided into I, II, and III areas based on the degree of liquefication. The surface subsidence is significantly related to Arias intensity and is concentrated within the range of 5 %–95 % of the intensity. The structural floating is synchronized with the liquefaction of the saturated sand, and the uneven floating and inclination of the underground structure are remarkable, anti-flotation design of underground structures should take into account differences in section forms. During the liquefaction of saturated sand, the foundation soil has conspicuous lateral deformation, especially in the deep soil layer. The shape of the dynamic earth pressure increments turns from triangular to linear, when the foundation soil changes from non-liquefied to liquefied. Compared with the limiting values of the elastic inter-story drift ratio, the maximum inter-story drift ratio of the structure is smaller. The tensile strain responses on the columns, particularly in the lower layer, are more prominent than those at the slabs and side walls.

Liquefaction susceptibility of beach sand containing plastic fines

Liquefaction of saturated sand containing fines can be triggered due to propagation of seismic waves or by monotonically increasing loads. In such circumstances excess pore-water pressure development results in loss of confinement and decreased intergranular force transfer, leading to strain-softening behaviour. This research assesses the effect of plastic fines on the liquefaction susceptibility of carbonate sand from Famagusta Bay, Cyprus (Mediterranean Region). The study simulates the diverse composition of sand by incorporating varying proportions of silt and clay. Consolidated undrained triaxial compression tests were conducted to analyse the effect of fines on stability/instability, compressibility and location of critical state lines at low-stress levels of 50, 100 and 150 kPa with relative densities of 35% and 70%. Silt and clay fractions (10, 20, 30%) were incorporated into the sand to form a set of mixed soils. Sand and clayey-silty sand (10%) specimens prepared at loose state exhibited flow behaviour whereas diverse behaviour is observed for other soil groups. The prevention of instability can be attributed to the mineralogical nature of fines that amalgamated the soil structure.

Study on Seismic Damage Mechanism of Dredger Fill Ground in Tianjin Binhai Area

Tianjin binhai new area has a large area of dredger fill groud, And it is easy to produce dredger fill seismic settlement and saturated sand liquefaction under earthquake action. We simulate seismic subsidence state of Dredger Fill and liquefaction state of saturated sand under the 50-year probability of exceedance of 10% and 2% probability level earthquake by using Finn constitutive model in a certain soft foudition of Tianjin binhai new area. The results show that: Both seismic subsidence and liquefaction of saturated sand are the transition process from effective stress to pore water pressure. Moreover, dredger fill and saturated sand soil in the stronger the earthquake and the shallower buried depth are more likely to collapse and liquefaction.

Compaction and Liquefaction of a Sandy Layer: Simulation of Shaking Table Experiments

AbstractThis paper presents numerical simulations of the behavior of a sandy layer subjected to a cyclic horizontal acceleration in shaking table tests, with a particular attention focused on the settlements of a dry sand layer, and on the liquefaction of saturated sand. A compaction/liquefaction model (C/L) is applied to these simulations. The influence of specific parameters of the model on the compaction and liquefaction of a sandy layer is shown and discussed. The results of simulations are compared with selected experimental data.

A Study of Liquefaction Resistance of Composite Foundation of CFG and Stone Columns

Liquefaction of saturated sands remains an important topic in Geotechnical earthquake engineering. Amongst various review measures available,the use of CFG Column and stone columns Composite foundation to prevent liquefaction can achieves good results. In this paper, a detailed review on effectiveness of densification, drainage and reinforcement of CFG column and stone columns Composite foundation for the resistance of soil liquefaction during earthquakes is presented.

Sand volcanoes in the Avon–Heathcote Estuary produced by the 2010–2011 Christchurch Earthquakes: implications for geological preservation and expression

Sand volcanoes produced by liquefaction of saturated sands were widespread in the Avon–Heathcote Estuary following individual major events of the Christchurch 2010–2011 Earthquake sequence. Sand volcanoes were composed of fine grey sands and varied in diameter over the range 0.2–5 m, fed by vertical to subvertical feeder pipes of 15–25 cm diameter that cross-cut mud and shell horizons. Tides and wind-driven waves reduced, and at times removed, the profile of surface features; however, subsurface features remained unaffected. The geological signature of these volcanoes, formed in wet sandy tidally influenced settings such as estuaries, would be preservation of straight-sided feeder pipes 15–25 cm in diameter, >30 cm in length that cross-cut undeformed strata with or without expression of the erupted cone. Sediments were not able to be excavated beneath the shallow water table, and all observed feeder conduits occurred as roughly cylindrical pipes rather than elongated planar dykes; this does not preclude dykes being present deeper in the subsurface, however. Coseismic subsidence may enhance the preservation potential of surface features by increasing relative water depth, thereby increasing sedimentary accommodation space, and decreasing the influence of wave action in removing cones.

Deduction and experimental investigation of constitutive relation of liquefaction of saturated sand

According to the existing problems of liquefaction models of saturated sand that were put forward under dynamic action, on the basis of Handin-Drnevich model, a new calculating model of the dynamic constitutive relation of saturated sand was put forward. The model was based on the basic hypothesis of instantaneous limit balance according to the basic principle that the stress estate is the destroyed condition was not overstepped. The calculated method of increment nonlinear was referenced and combined with the excellence of the model of distributed particles. The process of vibrating liquefaction of saturated sand was divided into some areas. And the phenomena of shearing dilatation and unloading shrink of saturated sand were considered. On above basic a new calculating constitutive relation model was proposed. There are a few parameters in the model. The physical means of the parameters are very evident and quantized. They could be obtained from the dynamic triaxial test in door. The model was contrasted and validated with the results of the dynamic triaxial test in door. The comparison of the results of the dynamic triaxial test in door and the calculating results of the model indicates that all sorts of phenomenon appearing in the process of liquefaction of saturated sand could be more perfectly reflected by the model. Especially at the initial stage of development of pore water pressure and strain of saturated sand, the results of the dynamic triaxial test in door are consistent with the calculated results of the model very much. But there is some difference between the results at the anaphase of development of pore water pressure and strain. On the path of stress, the calculating and experimenting ultimate state surfaces are almost identical.

表面波探査と動的弾塑性ＦＥＭに基づく緩傾斜宅地の簡易な耐震性能評価

Two typical suffering cases of slightly-inclined residential ground at the time of Mid Niigata Prefecture Earthquake 2004 are examined. Around the houses on the thickly filled ground, large residual settlement was observed clearly. Probably, the liquefaction of saturated sand in the ground may be related to the damage. In this study, the mechanism of damage is examined based on the 2-D dynamic elasto-plastic finite element method. In the analysis, the material parameters have been determined based on the distribution of shear wave velocity in the ground, which was estimated by the surface-wave investigation. It is shown that the dynamic elasto-plastic finite element analysis with the surface-wave investigation is very effective for the evaluation of the seismic stability of the ground.

Liquefaction and displacement of saturated sand under vertical vibration loading

In order to investigate the influence of the vertical vibration loading on the liquefaction of saturated sand, one dimensional model for the saturated sand with a vertical vibration is presented based on the two phase continuous media theory. The development of the liquefaction and the liquefaction region are analyzed. It is shown that the vertical vibration loading could induce liquefaction. The rate of the liquefaction increases with the increase of the initial limit strain or initial porosity or amplitude and frequency of loading, and increases with the decrease of the permeability or initial modulus. It is shown also that there is a phase lag in the sand column. When the sand permeability distribution is non-uniform, the pore pressure and the strain will rise sharply where the permeability is the smallest, and fracture might be induced. With the development of liquefaction, the strength of the soil foundation becomes smaller and smaller. In the limiting case, landslides or debris flows could occur.

Application of artificial network in forecasting liquefaction of saturated sandy soil

The forecasting of liquefaction of saturated sand is difficult because of its complexity, but it is of importance in practice. The technique of artificial neural network is used to model the forecasting of liquefaction phenonmenan. The dimension analysis is processed, based on which a concise architecture of BP network is built then. It is shown that artificial neural network is an effective tool in forecasting of liquefaction.

Possible continuum theory for densification and liquefaction of saturated sand : Ahmadi, G J Int Assoc Math Geol, V13, N1, Feb 1981, P37–52

Possible continuum theory for densification and liquefaction of saturated sand : Ahmadi, G J Int Assoc Math Geol, V13, N1, Feb 1981, P37–52

A possible continuum theory for densification and liquefaction of saturated sand

A previously developed continuum theory of granular media is applied to the problems of densification and liquefaction of saturated sand. An expression for the free energy of saturated sand is developed. The process of densification of sand subjected to cyclic shear stress is studied and several expressions for an increase of the solid volume fraction are obtained and discussed. The problem of the initial liquefaction of saturated sand samples under cyclic shear stress is then considered and several criteria relating the shear stress amplitude, over-burden pressure, time to liquefaction, and physical properties of the sand sample are established. Some semiempirical relations for field applications are also presented.

Undrained Cyclic Shear Behaviour Of Clay With Initial Static Shear Stress

A series of undrained cyclic triaxial compression tests has been performed on a high plastic marine clay. Testing was performed for not only isotropically but also anisotropically consolidated specimens under various combinations of initial static and subsequent cyclic shear stresses. The cyclic shear strength was first discussed, and then, residual shear strain was investigated related with effective stress ratio at the peak of cyclic stress. Based on the experimental results, a semi-empirical model was proposed for evaluating the development of residual shear strain during cyclic loading. The model successfully explained the behaviour of clay subjected to various magnitude of initial static and subsequent cyclic shear stresses. INTRODUCTION The main interest about the design problem against earthquake has been focused on liquefaction of saturated sands. Clays have been considered to be rather stable than sands during earthquake. However, serious damages of structures based on thick clay layers were reported in 1985 Mexico Earthquake (Seed et al. [6] , Mendoza et al. [2] ). A large deformation of ground due to amplification of seismic motion is recognized as a characteristic of clay behaviour during earthquake. Additionally, a lot of collapses of fills were caused by failure of clay base layers in 1964 Niigata Earthquake, 1978 Miyagiken-oki Earthquake and 1983 Nihonkai-chubu Earthquake in Japan. On the other hand, in the design of offshore platform against wave loading, the cyclic properties of clays have been investigated and taken in the practical design method (Andersen et al. [1] ). Although the Transactions on the Built Environment vol 3, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509

Cyclic Stress Conditions Causing Liquefaction of Sand

Liquefaction of saturated sand was studied using a cyclic loading triaxial test. Quantitative data were obtained providing numerical values for the several important factors necessary to produce liquefaction. Under cyclic loading, four different conditions must be considered; initial liquefaction, partial liquefaction, complete liquefaction, and failure. At relative densities below about 50%, these three conditions occurred almost simultaneously, whereas for relative densities above about 80%, a considerable number of stress cycles were required after initial liquefaction to develop large strains defining a failure condition. There was an approximately linear relationship between the relative density and the stress required to cause initial liquefaction in a given number of cycles. It was also found that the magnitude of cyclic stress required to cause initial Iiquefaction increases almost linearly with confining pressure. Suggestions are presented as to applications of this type of data in predicting the susceptibility of a field deposit to liquefaction during an earthquake.

Liquefaction of Saturated Sands During Cyclic Loading

Liquefaction of saturated sands was studied by means of pulsating loading triaxial tests on isotropically consolidated undrained laboratory samples. An analysis indicates that this type of test can be made to simulate idealized loading conditions on elements of soil in the field during earthquakes. The test results indicate that the danger of liquefaction of a saturated sand is determined by the following factors: (1) Void ratio; the higher the void ration the more easily liquefaction will occur. (2) Confining pressure; the lower the confining pressure the more easily liquefaction will occur, and (3) magnitude of cycle stress or strain; the larger the cyclic stress or strain the fewer the number of cycles required to induce liquefaction. Data from large shaking table experiments, and from observations of liquefaction during recent earthquakes lend qualitative support to the conclusions drawn from these laboratory cyclic loading triaxial tests.