Surface Ground Layers Research Articles

ESTIMATION OF PREDOMINANT PERIOD OF GROUND SURFACE LAYER USING THE INVERSE DISTANCE WEIGHTING METHOD

The evaluation of a site amplification effect is very important in the earthquake engineering when an earthquake damage distribution of wooden house will be predicted by an accurate estimation of seismic intensity. A predominant period in the microtremor H/V spectral ratio at ground surface corresponds to the natural period of surface ground layer. The microtremor H/V spectral ratio measurement was applied to the east district in Maizuru city. Both horizontal and vertical microtremors at 75 sites in the east district in Maizuru city were measured by servo type accelerometers, and the microtremor H/V spectral ratio and its predominant period at each site were evaluated from microtremor accelerations. Also, the predominant periods at 353 sites were numerically evaluated from the predominant periods measured at 75 sites by the Inverse Distance Weighting method.

S-wave impedance measurements of the uppermost material in surface ground layers: Vertical load excitation on a circular disk

S-wave impedance is one of the most effective parameters used to study the ground motion amplification of soil deposits. We propose a new approach to measure the S-wave impedance of the uppermost material in surface ground layers. First, a circular disk is set on the ground surface, and it is vertically loaded by sinusoidal wave excitation. When the time series of the loading velocity is synchronized with the reaction force, the ratio of the reaction force to the loading velocity is proportional to the S-wave impedance. We then estimate the proportionality coefficient from numerical experiments and check its accuracy. The measurement error is estimated to be within 1% for the homogeneous half-space case. We also discuss the applicability of this new approach and its limitations on the basis of numerical experiments for inhomogeneous media: a two-layered medium and a one-dimensional (1-D) random medium. The proposed approach is effective for both cases if we select the appropriate circular disk size.

The reason for synchronous disturbances in the atmospheric electric field and high-frequency geoacoustic emission during the seismotectonic process

The atmospheric electric field, the geoacoustic emission at frequencies of 0.7–2.0 kHz at three points, the volumetric activity of radon and thoron in the surface ground layer, the atmospheric pressure, the velocity of wind, and the intensity of rain were synchronously measured from August 27 to October 17, 2012, at the interception zone of various faults 41 km southwest of the town of Petropavlovsk-Kamchatskiy. It was found for the first time that the increase in radon and thoron concentration in the surface ground layer is accompanied by a decrease in the atmospheric electric field and simultaneous disturbance of the high-frequency geoacoustic emission. The stronger emission of these gases into the atmosphere due to the increase in velocity of the extension of subsurface sedimentary rocks during seismotectonic process is the most likely reason for the decrease in the electric field, which occured along with a geoacoustic disturbance.

A PRACTICAL SEISMIC RESPONSE ESTIMATION OF LOW-MEDIUM RISE R/C BUILDING WITH RELATIVELY HIGH STRENGTH CONSIDERING NONLINEAR SSI EFFECTS

In this paper, the influence of soil-structure interaction(SSI) effects on maximum displacement response of low-medium rise reinforced concrete building with relatively high strength are studied. A practical procedure with a simplified model including nonlinear SSI effects to predict maximum displacement response is proposed. Shear force-displacement relation and damping factor including SSI effects are obtained by using maximum displacements response of simplified model and surface ground layer due to strong ground motions. The maximum response estimation due to strong earthquake motions is demonstrated using example models of reinforced concrete 5-story building and surface ground deposit. The validity of proposed procedure is examined in comparison with the results of nonlinear response analysis using 2-dimentional FEM model.

Generalized Hashin–Shtrikman variational principle for boundary-value problem of linear and non-linear heterogeneous body

When the in-situ measurement of the effective properties is difficult, a ground or a crust of large dimensions is modeled as a body with probabilistically varying materials. As the variance of heterogeneity is large, conventional analysis methods require enormous numerical computation. As an alternative, this paper proposes the generalized Hashin–Shtrikman variational principle which provides upper and lower bounds for the expectation of the behavior of such a probabilistically varying body. The bounds are obtained by analyzing two fictitious bodies which are rigorously defined when probabilistic distributions of material properties are given. The generalized Hashin–Shtrikman principle can be applied to non-linear initial boundary-value problems. The fault formation process in surface ground layers is solved as an illustrative example. The surface layers are modeled as a probabilistically varying elasto-plastic body, and it is shown that the upper and lower bounds for the expectation actually bound the average behavior which is computed by the Monte-Carlo simulation. Discussions are made on these numerical results.

DISTRIBUIÇÃO DE CHUMBO NO PERFIL DE SOLO AVALIADA PELAS SOLUÇÕES DE DTPA E MEHLICH-3

Tendo em vista a possibilidade de aumentos significativos no conteúdo de Pb em solos cultivados perto de pólos industriais, procurou-se, no presente trabalho, avaliar a distribuição desse elemento no perfil de solo próximo e distante de uma fonte geradora, localizada entre a Rodovia Presidente Dutra e o núcleo urbano de Caçapava Velha (SP) e comparar procedimentos analíticos para extração de Pb em solos. Coletaram-se as amostras de solo a 500 e 1.000 m da fonte geradora, em quatro direções (N, S, E e W) e nas profundidades de 0-5, 5-10, 10-20, 20-40 e 0-20 cm. A extração de Pb foi feita com a solução de DTPA e de Mehlich-3 (M-3), sendo as mais altas concentrações de Pb encontradas nas amostras de solos localizadas próximo à fonte geradora. Verificou-se claramente que o Pb tendeu a acumular-se na camada superficial, diminuindo com a profundidade. Concluiu-se que as soluções de DTPA e de M-3 foram eficientes para avaliar a contaminação por Pb, podendo ser utilizadas no monitoramento do impacto ambiental causado por esse elemento.

Aseismic Design Method Using Response SpectraIncluding Liquefaction And Ground Improvement

Effective design method for response spectra of a single degree of freedom (SDOF) structure taking into consideration liquefaction of ground layer and ground improvement by the compacting method is presented. This method consists of the 2D effective stress analysis of surface ground layers, the simulating analysis of the sand compaction pile method and the seismic response analysis of a SDOF structure. The renewal natural period of the ground due to the ground improvement and the natural period of a SDOF structure are used as two key parameters for evaluating response spectra. Results of numerical computation show that the natural periods of the ground and a SDOF structure are useful for aseismic design of a SDOF structure and the ground improvement works to reduce the responses of a SDOF structure with the long natural period.