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31.
Effects of inertial and kinematic interaction on seismic behavior of pile with embedded foundation 总被引:4,自引:0,他引:4
Kohji Tokimatsu Hiroko Suzuki Masayoshi Sato 《Soil Dynamics and Earthquake Engineering》2005,25(7-10):753-762
Effects of inertial and kinematic forces on pile stresses are studied based on large shaking table tests on pile-structure models with a foundation embedded in dry and liquefiable sand deposits. The test results show that, if the natural period of the superstructure, Tb, is less than that of the ground, Tg, the ground displacement tends to be in phase with the inertial force from the superstructure, increasing the shear force transmitted to the pile. In contrast, if Tb is greater than Tg, the ground displacement tends to be out of phase with the inertial force, restraining the pile stress from increasing. With the effects of earth pressures on the embedded foundation and pile incorporated in, pseudo-static analysis is conducted to estimate maximum moment distribution in pile. It is assumed that the maximum moment is equal to the sum of the two stresses caused by the inertial and kinematic effects if Tb<Tg or the square root of the sum of the squares of the two if Tb>Tg. The estimated pile stresses are in good agreement with the observed ones regardless of the occurrence of soil liquefaction. 相似文献
32.
The role of the seismic trigger in the Calitri landslide (Italy): historical reconstruction and dynamic analysis 总被引:2,自引:0,他引:2
Salvatore Martino Gabriele Scarascia Mugnozza 《Soil Dynamics and Earthquake Engineering》2005,25(12):933-950
The study covered by this paper was focused on the historical case of the Calitri landslide, which was repeatedly reactivated by earthquakes, as reported since 1694. The town of Calitri (Southern Italy) is located on a ridge whose southern slope, from its top to the Ofanto river valley floor, has been historically affected by major landsliding. The last record of recurrence of the Calitri landslide leads back to the 1980 Irpinia earthquake, which caused significant damage to the town and had pervasive and visible ground effects. Based on a detailed historical reconstruction of landsliding and seismicity at Calitri, the study analysed the current static and dynamic stability of the landsliding slope by means of a finite-difference numerical analysis, taking into account the various factors of landslide initiation and kinematics. The results of the numerical analysis: (i) were consistent with the roto-translational mechanism observed upon the latest reactivation of the landslide; (ii) demonstrated that excess pore pressure redistribution caused a lag between the seismic trigger and the initiation of landsliding; and (iii) showed the impact of seismic input frequency on propagation and depth of slope instability. 相似文献
33.
The dynamic characteristics and migration of a pyramid dune 总被引:6,自引:0,他引:6
TAO WANG WEIMIN ZHANG ZHIBAO DONG JIANJUN QU ZHEFAN JING WANFU WANG JIANMIN FENG 《Sedimentology》2005,52(3):429-440
The results of wind tunnel experiments and field observations show that when the intersection angle between airflow direction and dune crest (ridge) line is > 30°, a reverse vortex is formed. Because of the convergence of sand streams from the windward and lee slopes at the crest, sand accumulates in the crestal region, causing vertical growth. Nevertheless, studies also show that the common asymmetry of the two slopes of a dune may significantly influence the evolution of arms of a pyramid dune. The migration rates of pyramid dunes are mediated by the interplay of their arms moving transversely and the vertical growth in response to the variations in wind regimes. Comparing the effects of airflow transverse to a given arm with longitudinal airflow, it is indicated that the transverse airflow is more significant in controlling the arms of pyramid dunes. The whole body of the studied pyramid dune, particularly the upper quarter section, migrated SE direction during the monitoring period. The patterns of wind erosion and deposition change alternately with seasonal variations in wind directions. The W, NE and SE sides undergo constant erosion, deposition and both erosion and deposition, respectively. The results of long-term monitoring of a pyramid dune show that southerly winds, resulting from a local circulation, markedly affect the transverse migration of the whole pyramid dune. 相似文献
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35.
Rocks can be modeled in a continuum framework as fissured, poroelastic materials, i.e., materials with two degrees of porosity, one due to the fissures and another one due to the pores. The governing equations of motion of fissured poroelastic rocks established by Beskos are rederived here by establishing a variational statement which also provides the boundary conditions of the problem. This is accomplished by considering strain, dissipation and kinetic energies as well as the work of external forces. The above statement is also derived here by employing the method of weighted residuals. 相似文献
36.
To a set of well-regarded international scenarios (UNEP’s GEO-4), we have added consideration of the demand, supply, and energy implications related to copper production and use over the period 2010–2050. To our knowledge, these are the first comprehensive metal supply and demand scenarios to be developed. We find that copper demand increases by between 275 and 350% by 2050, depending on the scenario. The scenario with the highest prospective demand is not Market First (a “business as usual” vision), but Equitability First, a scenario of transition to a world of more equitable values and institutions. These copper demands exceed projected copper mineral resources by mid-century and thereafter. Energy demand for copper production also demonstrates strong increases, rising to as much as 2.4% of projected 2050 overall global energy demand. We investigate possible policy responses to these results, concluding that improving the efficiency of the copper cycle and encouraging the development of copper-free energy distribution on the demand side, and improving copper recycling rates on the supply side are the most promising of the possible options. Improving energy efficiency in primary copper production would lead to a reduction in the energy demand by 0.5% of projected 2050 overall global energy demand. In addition, encouraging the shift towards renewable technologies is important to minimize the impacts associated with copper production. 相似文献
37.
38.
Based on the dynamic analysis and research of pollution risk of groundwater sources, this paper creates the dynamic assessment method of pollution risk of groundwater source area under the theory of “source-pathway-receptor”, and applies this method to one typical fissure karst groundwater source area in northern China. Following the 30-year petroleum pollutant migration simulation and pollution risk assessment of groundwater source area, this study finds that the very high risk zone is mainly located in Q Petrochemical Company and the surrounding area and the area adjacent to River Z. Within this period of thirty years, the pollution risk of groundwater source area has showed a dynamic trend that features an inverted “V” shape. The ratio of very high risk zone to the total area will be 18.1%, 17.47% and 16.62% during the tenth year, the twentieth year and the thirtieth year separately, and will reach the highest level of 19.45% during the fifteenth year. Meanwhile, the vertical migration distance of pollutant centre concentration changed from the surface soil at the outset to the deepest point of about 250 meters underground during the tenth year. The results of this risk assessment indicate the dynamic feature of pollution risk. The dilution, degradation and migration of petroleum pollutants in groundwater system contribute to an ultimate decline in pollution risk. 相似文献
39.
Abhishek Kumar Singh Anirban Lakshman Amares Chattopadhyay 《Geomechanics and Geoengineering》2016,11(3):201-218
Heterogeneity, being a trivial feature inside the earth or in a geostructure, makes a strong basis for its consideration in the study of geomechanics. Inclusion of the concept of heterogeneity along with irregularity in the medium brings a novelty to the existing literature related to the study of the moving load. The present study investigates the effects of linear and exponential heterogeneity on the dynamic response due to a normal load moving with constant velocity on a rough irregular heterogeneous isotropic half-space in a comparative approach. Expressions for both normal and shear stresses for either case of heterogeneity have been established in closed form. Substantial effects of the affecting parameters such as depth, irregularity factor, maximum depth of irregularity, frictional coefficient, linear heterogeneity parameter and exponential heterogeneity parameter on normal and shear stresses for both the cases of heterogeneity have been observed. Numerical computation has been carried out and the effects of said parameters have been meticulously examined by means of graphs. Moreover, different cases of heterogeneity and homogeneity along with various types of irregularity namely rectangular, parabolic and no irregularity are compared which serve as a focal theme of the study. 相似文献
40.
对北仑河口自然环境动力要素的分析表明 ,河川径流、波浪、沿岸流及潮流是北仑河口演变的主要动力因素 ,三者的叠加不但使河道的大小、位置、形态等发生变化 ,而且还造成河岸的严重侵蚀 相似文献