Influence of fines content on the undrained cyclic shear strength of sand–clay mixtures

A series of undrained cyclic triaxial tests were performed on sand–clay mixtures with various sand–clay mixing ratios. Prior to the primary tests, the threshold fines content was examined by consistency tests, which was found to be approximately 20%. For sand–clay mixtures with a sand-matrix (fines content less than the threshold fines content), the cyclic shear strength of low-density mixtures increases and that of high-density mixtures decreases with increasing fines content. However, for sand–clay mixtures with a fines-matrix (fines content greater than the threshold fines content), there exists a unique correlation between the cyclic shear strength and global void ratio for different fines content. The equivalent granular void ratio is introduced in this paper to account for the contribution ratio of the fines to soil skeleton. As a result, a unique relationship between cyclic shear strength and equivalent granular void ratio was observed for pure sand and sand–clay mixtures with a sand-matrix.     

Effect of wave–bedform feedbacks on the formation of,and grain sorting over shoreface-connected sand ridges

The influence of wave–bedform feedbacks on both the initial formation of shoreface-connected sand ridges (sfcr) and on grain size sorting over these ridges on micro-tidal inner shelves is studied. Also, the effect of sediment sorting on the growth and the migration of sfcr is investigated. This is done by applying a linear stability analysis to an idealized process-based morphodynamic model, which simulates the initial growth of sfcr due to the positive coupling between waves, currents, and an erodible bed. The sediment consists of sand grains with two different sizes. New elements with respect to earlier studies on grain sorting over sfcr are that wave-topography interactions are explicitly accounted for, entrainment of sediment depends on bottom roughness, and transport of suspended sediment involves settling lag effects. The results of the model indicate that sediment sorting causes a reduction of the growth rate and migration speed of sfcr, whereas the wavelength is only slightly affected. In the case where the entrainment of suspended sediment depends on bottom roughness, the coarsest sediment is found in the troughs; otherwise, the finest sediment occurs in the troughs. Compared to previous work, modeled maximum variations in the mean grain size over the topography are in better agreement with field observations. Settling lag effects are important for the damping of high-wavenumber mode instabilities such that a preferred wavelength of the bedforms is obtained.     

Evaluation of the effect of earthquake frequency content on seismic behavior of cantilever retaining wall including soil–structure interaction

A three-dimensional backfill–structure–soil/foundation interaction phenomenon is simulated using the finite element method in order to analyze the dynamic behavior of cantilever retaining wall subjected to different ground motions. Effects of both earthquake frequency content and soil–structure interaction are evaluated by using five different seismic motions and six different soil types. The study mainly consists of three parts. In the first part, following a brief review of the problem, the finite element model with viscous boundary is proposed under fixed-base condition. In the second part, analytical formulations are presented by using modal analysis technique to provide the finite element model verification, and reasonable agreement is found between numerical and analytical results. Finally, the method is extended to further investigate parametrically the effects of not only earthquake frequency content but also soil/foundation interaction, and nonlinear time history analyzes are carried out. By means of changing the soil properties, some comparisons are made on lateral displacements and stress responses under different ground motions. It is concluded that the dynamic response of the cantilever wall is highly sensitive to frequency characteristics of the earthquake record and soil–structure interaction.     

Effect of the Madden–Julian Oscillation and Quasi-Biennial Oscillation on the Dynamics of Extratropical Stratosphere

Geomagnetism and Aeronomy - The effects of the Madden–Julian oscillation and quasi-biennial oscillation in the equatorial stratosphere on the dynamic processes in the extratropical...     

Effect of deposit alterations on the dating of herbivorous teeth from Arago cave by the ESR–U-series method

Geochemical alteration processes in archaeological sites may affect the environmental dose rate during the burial history and cause inaccuracy in age determination by palaeodosimetric dating methods, such as luminescence or ESR. In Arago Cave (Tautavel, France), the original composition of the sandy aeolian sediments of palaeoanthropological level G, where the Homo heidelbergensis Arago XXI skull was found, has been modified by both carbonation and phosphatization processes. Eight fossil teeth were collected from different geochemically affected parts of level G and analyzed by the ESR–U-series method. All the teeth are presumably contemporaneous. The results show that the samples from the phosphated area agree within error with those from the carbonated area. Surprisingly, the samples from the non-altered area show ages 100–150 ka younger. This difference is mainly due to the remarkable changes in the gamma dose rate over time. The measured in situ dose rate accounts for more than 50% of the total dose rate for all the samples. We observed that the samples' equivalent dose (D_E) were generally 20% lower in the non-altered area than in the carbonated and phosphated ones. These results show the crucial effect of the geochemical processes affecting the age calculation by ESR–U-series method in comparison with independent chronological data.     

Effect of climate changes on the maximal runoff in the Amur Basin: Estimation based on dynamic–stochastic simulation

The potentialities of dynamic–stochastic simulation are analyzed as applied to changes in the regime of summer–autumn rain-flood runoff, which is the governing phase of water regime in the Amur Basin. The scenario of climate changes was formulated in a maximally generalized form as an increase in the sum of seasonal precipitation by an amount of up to 20% of its average long-term value; therefore, all obtained estimates are to be regarded as tentative. Notwithstanding the relatively poor support by observation data, a regionally adapted hydrological model with a flood cycle model (FCM) as its core yields reliable and convincing results. The most important conclusion regards the possible disproportionate response to a climate impact, i.e., the relative increase in minimal-runoff characteristics is far in excess of the assumed increase in the total precipitation.     

Effect of dynamic soil–bridge interaction modeling assumptions on the calculated seismic response of integral bridges

In this study, the effect of soil–structure modeling assumptions and simplifications on the seismic analyses results of integral bridges (IBs) is investigated. For this purpose, five structural models of IBs are built in decreasing levels of complexity starting from a nonlinear structural model including close numerical simulation of the behavior of the foundation and backfill soil and gradually simplifying the model to a level where the effect of backfill and foundation soil is totally excluded. Nonlinear time history analyses of the modeled IBs are then conducted using a set of ground motions with various intensities representing small, medium and large intensity earthquakes. The analyses results are then used to assess the effect of modeling complexity level on the calculated seismic response of IBs. The nonlinear soil-bridge interaction modeling assumptions are found to have considerable effects on the calculated seismic response of IBs under medium and large intensity earthquakes.     

Ozone content of the atmosphere. 1. Climatological characteristics of the total ozone content in the 100–110° E longitudinal zone

The results of a periodogramanalysis of the variations in the ionospheric parameters, measured using the vertical radio sounding method at midlatitude Irkutsk observatory (Eastern Siberia), are presented. The 1984–1986 period of observations was used. It has been indicated that the statistically significant oscillations with periods typical of planetary waves are present in the variations in f ₀E_s, f _bE_s, h′E_s, f _min, f ₀F2, and h′F.     

Application Effect of CEMP in the Foreland Basin on the Western Edge of Ordos

Foreland basins on the western edge of Ordos are characterized by typical loess geomorphologic features. Its surface is severely cut, and its underground geological structures are complicated.Making use of the advantage of CEMP in exploration in frontland as well as successful multi-year exploration experiences in West China, we first employed the CEMP method to conduct exploration on the western edge of the Ordos basin and its surrounding areas. The practices proved that rich and reliable geological results have been achieved with the CEMP method in complicated areas covered with loess. This can provide important evidence for researching the contact relationship among basins and mountains, structural feature of target layers and predict favourable areas.     

Analysis of the liquefaction phenomena in the village of Vittorito (L��Aquila)

This paper describes a case-history of liquefaction occurred near the village of Vittorito after the April 6, 2009 L’Aquila earthquake (moment magnitude M_w = 6.3), approximately 45 km far from the epicentre. In the document, first, an estimation of the seismic motion in the area has been made. Thereafter, the performed geotechnical investigation is described, followed by the application of some fast assessment criteria for the occurrence of liquefaction, recently proposed by the new Italian Building Code. A careful assessment of all the parameters involved in conventional Seed and Idriss (1971) liquefaction analyses is considered. The cyclic resistance ratio CRR is evaluated by cone penetration tests CPT and by in situ seismic dilatometer tests SMDT; in the latter case CRR is evaluated by different empirical correlations with shear wave velocity V_s and horizontal stress index K_D. Analytical data confirmed the observed occurrence of the liquefaction in Vittorito, even if the acceleration field in the area, produced by the L’Aquila earthquake, was very low.     

Preliminary Study on the Effect of Borehole on Seismic Waves in the Deep Borehole Observation System

There has been an increasing tendency to adopt the deep borehole technique for seismic observation.This paper deals with the effect of borehole on seismic waves in the deep borehole system and obtains the conclusion that,within the frequency range of seismic waves,the existence of a borehole has no effect on the horizontal component of a three-component seismometer in the borehole and has only a limited effect on the vertical component.To the first approximation,the difference between the borehole record and ground surface record of seismic waves can be attributed to the difference in seismometer deployment. This conclusion would be useful for the integrated utilization of borehole records and ground surface records of seismic waves.     

Experimental study on the relation between the water content of surface soil and theacoustic wave

Introduction Earthquake is not an isolated event. The focal region is not a closed system either. It is able to exchange energy or material with the medium outside this region. These kinds of exchange may cause various physical and chemical effects, so it is possible to get precursory signals by using space remote sensing technology. Many scholars (QIANG, et al, 1990; GENG, et al, 1992; XU, et al, 1995) have carried out some preliminary researches and experiments on the mechanism of therm…     

Earthquake behavior of variable rupture-scale on active faults and application of the cascade-rupturing model

IntroductionThe earlier concept of the characteristic earthquakes means those earthquakes recurring along the same portion of active fault zones, and having nearly the same size, displacement and rupture scale (Schwartz, Coppersmith, 1984). However, more and more evidences have suggested that the rupture(s scale of earthquakes recurred on an individual fault portion has variability (Thatcher, 1990). For instance, the rupture of the 1906 San Francisco, California, earthquake with magnitude 8.…     

Effect of compressibility on the generation of hydrodynamic helicity in the Earth’s liquid core

By the example of a standard three-dimensional model of thermal convection in a rotating spherical shell, it is shown how radial density gradient ?_ρ affects the generation of hydrodynamic helicity χ. For example, the generation of χ weakly depends on ?_ρ inside a Taylor cylinder and, outside the cylinder, the compressibility of the liquid amplifies the generation of χ. The consequences for the geodynamo theory are considered.