Liquefaction Characteristics Of Sand Research Articles

Investigation of sand liquefaction potential in cyclic triaxial test and some premilinary research results in Vietnam

In the world, cyclic triaxial tests are widely used to evaluate the liquefaction potential of soil and determine the cyclic parameters for seismic design. However, the application of cyclic trixial test for evaluation of soil liquefaction is still limited in Vietnam. This paper introduced the cyclic triaxial apparatus, method and testing procedure to access the liquefaction potential of sand under cyclic loading. The research on some saturated sandy soils with high fine-grained content in Vietnam showed that the research results of soil liquefaction potential is reliable. In which, the liquefaction characteristics of sand are evaluated based on the changes of stress, strain and pore water pressure according to the cyclic cycles, thereby determining the liquefaction point and liquefaction boundary for fine sandy soils at different density levels.

Experimental Study on Strength and Liquefaction Characteristics of Sand under Dynamic Loading

To investigate the influence of moisture content, density, and loading frequency on the dynamic strength and liquefaction characteristics of sandy soil, a series of vibration triaxial tests were designed and conducted. The tests were divided into incremental loading tests and cyclic loading failure tests. The results of the incremental loading tests indicated that the shear modulus decreases with increasing moisture content and density, while it increases with increasing loading frequency. The damping ratio of unsaturated samples showed no significant correlation with moisture content, whereas samples with a density above 50% exhibited an increasing trend in damping ratio with increasing density. The damping characteristics of the sandy soil were found to be related to the loading frequency, exhibiting the characteristics of viscous damping. The results of the cyclic loading tests revealed that the dynamic failure mode of the sand soil is the ultimate equilibrium failure mode. Increasing moisture content and decreasing density make the samples more susceptible to failure. During the process of cyclic loading leading to dynamic failure, the shear modulus of unsaturated samples remains constant, while the shear modulus of saturated samples gradually decreases. The damping ratio of saturated soil is significantly higher than that of unsaturated soil. During the process of cyclic loading leading to dynamic failure, the damping ratio of saturated soil shows no apparent correlation with loading frequency, but it decreases with increasing density.

Experimental Study on Liquefaction Characteristics of Saturated Sands Mixed with Fly Ash and Tire Crumb Rubber

The liquefaction of saturated sandy soils during dynamic loading can inflict excessive damage on the structures, leading to significant human and economic losses. Recycling and reusing industrial waste materials may offer a sustainable and economic solution to this problem. This study investigates the influence of two waste materials, namely, recycled fly ash and tire crumb rubber, on the liquefaction characteristics of sand. For this purpose, loose and medium-dense triaxial specimens were prepared using sand–fly ash mixtures containing 0–40% of fly ash and sand–tire crumb rubber mixtures containing 0–30% of crumb rubber. The liquefaction characteristics of the specimens were examined through a series of stress-controlled, undrained, dynamic triaxial tests. The tests were conducted at 1 Hz loading frequency and under initial effective confining stresses of 50 and 100 kPa. The experimental results showed that, at a similar relative density, the liquefaction resistance of the sand–fly ash specimens decreased as the fly ash content (FA) increased up to about 20%; then, it slightly increased until FA reached 40%. Sand-only specimens showed greater liquefaction resistance than sand–fly ash specimens. The liquefaction resistance of the sand–tire crumb rubber specimens was enhanced by increasing the rubber content (RC) in the mixtures. It was found that the increasing liquefaction resistance of sand with the addition of tire crumb rubber was more noticeable under higher confining stresses.

Liquefaction Characteristics of Sand With Polypropylene Fiber at Low Confining Stress

The present study evaluates the liquefaction characteristics of Ottawa sand with polypropylene fiber using cyclic triaxial test. A series of stress-controlled cyclic triaxial tests were performed at 34.47 kPa (5 psi) effective confining pressure. Specimens of clean Ottawa sand, and sand containing 0.05, 0.075, 0.1, and 0.3% polypropylene fiber by dry weight of sand were tested at 0.2, 0.25, 0.3, and 0.4 Cyclic Stress Ratio (CSR). Results show that a significant improvement in liquefaction resistance when the polypropylene fiber content exceeded beyond 0.075% at 34.47 kPa effective confining stress.

Study on consolidation and liquefaction characteristics of sand with cementation effect

Study on consolidation and liquefaction characteristics of sand with cementation effect

Saturation and Preloading Effects on the Cyclic Behavior of Sand

In order to study pore water pressure response and liquefaction characteristics of sand, which has previously experienced liquefaction, two series of cyclic triaxial tests were run on medium dense sand specimens. In the first test series the influence of the soil saturation under undrained cyclic loading has been studied. It summarizes results of cyclic triaxial tests performed on Hostun-RF sand at various values of the Skempton’s pore-pressure coefficient. Analysis of experimental results gives valuable insights on the effect of soil saturation on sand response to undrained cyclic paths. In the second series of tests, the preloading influence on the resistance to the sands liquefaction has been realized on samples at various histories of loading. It was found that a large preloading induces a reduction of the resistance of sands to liquefaction.

Effects of Different Consolidation Conditions on Liquefaction Resistance and Small Strain Quasi-Elastic Deformation Properties of Sands Containing Fines

In order to investigate the effects of different consolidation conditions on liquefaction characteristics of sands containing fines, a series of undrained cyclic triaxial liquefaction tests was performed on artificial samples prepared by mixing Toyoura sand and bentonite at a ratio of 95% to 5% by dry weight. Some specimens were isotropically consolidated for i, 20 or 100 days at a regular temperature, while the others were consolidated for 2 or 5 days while heating the cell water up to 60 degrees centigrade. Over-consolidated specimens with OCR of 2 and 4 were also prepared at a regular temperature. During consolidation and cyclic triaxial shearing of several specimens, their quasi-elastic deformation properties were measured while applying very small amplitude cyclic axial loads. Longer consolidation time, higher temperature during consolidation or higher ratio of over-consolidation resulted in an increase in the liquefaction resistance, with the exception that the liquefaction resistance of specimens consolidated for 100 days was not larger than that of specimens consolidated for 20 days. On the other hand, such different consolidation conditions affected the change in the quasi-elastic deformation properties in different manners. Development of cementation was suggested to have occurred during consolidation under high temperature. Reduction in the extent of anisotropy was suggested to have occurred during over-consolidation, which was accompanied by a decrease in the negative dilatancy at the initial part of shearing.

Resonant Column Testing of Sands with Different Viscosity Pore Fluids

The effect of pore fluid viscosity on the stiffness, damping, and liquefaction characteristics of sands was investigated to assess the potential contributions to a centrifuge model seismic response for soils saturated with high-viscosity pore fluid. Resonant column tests with cyclic loading frequencies in the range of 20–45 Hz were performed on a variety of fluids and sand sizes. At a strain level less than 2 x 10\u–\u4, the damping increased with pore fluid viscosity and shear strain amplitude, and it decreased with sand particle size. However, at shear strain greater than about 2 x 10\u–\u4, the increased skeleton damping tended to mask any effect of additional damping due to fluid viscosity. The liquefaction tests on fine silica sand revealed that the increase in total energy dissipation was not more than 10% for 100 cS oil when compared with water at a driving frequency of 25 Hz. Based on the experimental results, a simple model is proposed to examine the dependency of viscous damping on pore fluid viscosity, loading frequency, particle size, and shear strain amplitude.

Soil Liquefaction Evaluations by Elastic Shear Moduli

Cyclic triaxial tests were carried out on sands with different densities and stress histories to investigate the possible relationship between liquefaction characteristics and elastic shear modulus. The apparatus was designed so that the modulus and strength of a sample could be measured consecutively. The result shows that: (1) the elastic shear modulus can reflect soil fabric, relative density, and stress-strain and overconsolidation history effects all of which have a significant influence on the liquefaction characteristics of sands; and (2) a reasonable good correlation would exist between liquefaction characteristics and shear modulus for a given soil under given confining stresses. To study the possible use of shear moduli for liquefaction evaluations, another series of tests were conducted on undisturbed samples of sands. The sample obtained by tube sampling yields significantly lower undrained cyclic shear strength and modulus than those of the sample by in situ freezing which can secure good quality undisturbed samples. But a tube sample presheared to recreate the in situ elastic shear modulus and density provides liquefaction characteristics similar to those of the sample by freezing, indicating the effectiveness of shear moduli as an indicator for liquefaction evaluations.

Effects of Large Preshearing on Cyclic Behavior of Sand

ABSTRACT In order to study pore water pressure response and liquefaction characteristics of sand which has previously experienced liquefaction, two series of cyclic triaxial shear tests were run on loose saturated sand specimens in a static manner. In the first test series, sepcimens were subjected, at the end of the cyclic loading, to a large axial strain oriented to the triaxial compression under very low effective confining pressures in order to produce a state of liquefaction. After reconsolidation, the specimens were again subjected to the same sequence of cyclic stresses as before. The test results showed that the pore water pressure response and, hence, resistance to liquefaction of the presheared specimen was essentially the same in the second cyclic loading as the response of pore water pressures exhibited by the virgin specimen during the first cyclic loading. It was speculated that a newly formed cross anisotropic structure of the specimen during the application of the large preshear towards the triaxial compression had the same vertical axis of symmetry as that of the virgin specimen which was formed under gravity by the method of pulviation in water. In the second series of tests, a large axial strain oriented towards the triaxial extension was applied, at the end of the first cyclic loading, to a specimen under very small effective confining pressures, leading eventually to a state of liquefaction. After reconsolidation, the specimen was again subjected to the same sequence of cyclic stresses as before. It was found that the pore water pressure response in the second cyclic loading of the presheared specimen was different from the pore water pressure response exhibited by the virgin specimen during the first cyclic loading. This difference was ascribed to the fact that a newly formed cross anisotropic structure of the specimen formed during the application of the large preshear towards the triaxial extension had a horizontal axis of symmetry, as opposed to the vertical axis of symmetry preexistant in the virgin specimen formed by the method of pluviation in water. As a result of these observations, it was argued that a subsequent liquefaction of a sand which has previously been liquefied depends not only on the magnitude of preshear but more significantly on the direction of the preshear which is executed under very small confining pressures at the end of the previous cyclic loading.

Effects of overconsolidation and Ko conditions on the liquefaction characteristics of sands : Ishihara, K; Takatsu, H Soils Found, V19, N4, Dec 1979, P59–68

Effects of overconsolidation and Ko conditions on the liquefaction characteristics of sands : Ishihara, K; Takatsu, H Soils Found, V19, N4, Dec 1979, P59–68

Effects of Overconsolidation and K0, Conditions on the Liquefaction Characteristics of Sands

When overconsolidation is induced in a horizontal deposit of sand by the removal of surcharge pressure or by other events, the lateral deformation is prevented and the coefficient of earth pressure at rest, K 0 , increases. To evaluate effects of the overconsolidation ratio as well as increased K 0 -value on the liquefaction resistance of sand deposits, several series of cyclic torsion shear tests were carried out on samples of clean sand overconsolidated to different degrees under various K 0 -conditions. The results of these tests were summarized in an empirical formula. This formula is used to estimate the cyclic strength of sand at any given OCR and K 0 -values, based on the cyclic strength for isotropically and normally consolidated samples.