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991.
992.
993.
A comparative study of buried structure in soil subjected to blast load using 2D and 3D numerical simulations 总被引:5,自引:0,他引:5
The response of underground structures subjected to subsurface blast is an important topic in protective engineering. Due to various constraints, pertinent experimental data are extremely scarce. Adequately detailed numerical simulation thus becomes a desirable alternative. However, the physical processes involved in the explosion and blast wave propagation are very complex, hence a realistic and detailed reproduction of the phenomena would require sophisticated numerical models for the loading and material responses. In this paper, a fully coupled numerical model is used to simulate the response of a buried concrete structure under subsurface blast, with emphasis on the comparative performance of 2D and 3D modeling schemes. The explosive charge, soil medium and the RC structure are all incorporated in a single model system. The SPH (smooth particle hydrodynamics) technique is employed to model the explosive charge and the close-in zones where large deformation takes place, while the normal FEM is used to model the remaining soil region and the buried structure. Results show that the 2D model can provide reasonably accurate results concerning the crater size, blast loading on the structure, and the critical response in the front wall. The response in the remaining part of the structure shows noticeable differences between the 2D and 3D models. Based on the simulation results, the characteristics of the in-structure shock environment are also discussed in terms of the shock response spectra. 相似文献
994.
介绍了国家气象中心现行中期数值预报业务系统;介绍了预报模式的基本控制方程,在SP计算机上的实现过程;介绍了全球分析的并行处理方法和全球资料同化系统、后处理系统以及与之相关的配套系统。 相似文献
995.
强震预报的连续性方法与丽江7.0级地震预报 总被引:1,自引:1,他引:1
作继《云南强震活动的连续性探讨》后,提出云南强震活动的连续性方法:即一次强震前4个月内的中等地震丛集区几何中心150公里内地区,在经过数月至数年的孕育后将演变成强震发生区。据此连续性方法,1993年1月27日普洱6.3级地震后即在《震情研究》上预报“未来3-5年省内的7级大震将发生在永胜期纳(26.4°N,100.6°E)附近地区。另外,缅甸(22.5°N,98°E)也可能发生7-8级大震”。上 相似文献
996.
Based on a simplified media model of Gonghe area, the precursor characteristics of Gonghe M7.0 earthquake in 1990 are simulated in this paper by using the constitutive relationship of binary medium (solid and water).
The results show that the simulated state distribution and extension variation of media are identical with the spatial and
temporal distribution of reliable anomalies before Gonghe earthquake. The study also suggests that the development of the
Gonghe earthquake has experienced a series of processes such as elastic deformation of large scale, early nonelastic dilatation,
strain softening and elastic recovery in the neighbour region of Xining, nonelastic dilatation of high dense block near seismic
source and earthquake occurrence. Therefore, it can be concluded that this earthquake development is neither a simple process
for fissures developing and linking up with one another, nor a process of nonelastic volume expansion and water flowing into
medium around seismic source, contrary, it is a complicated medium state changing process, and the style of such changing
depends on geological structure environment of seismic source and its neighbour region. It is considered that different earthquakes
are accompanied by different geological conditions, the spatial and temporal behavior of their precursors are certainly different. 相似文献
997.
The postseismic vertical deformation rates of the 1990 Gonghe M
S=7.0 earthquake appears to have decreased exponentially. Based on Okada’s coseismic surface displacement solution caused by
a uniform fault slip in an elastic homogeneous half space, we derived its postseismic surface displacement by using a single-layer
standard linear solid model, and further derived a simplified formula for determining the effective relaxation time and viscosity
of the earth, which is independent of the dislocation parameters of the causative fault. From the postseismic vertical deformation
of the 1990 Gonghe earthquake, we inferred that the effective relaxation time defined by τ=η/μ is 2.6 years, and the effective viscosity η is about 1018 Pa · s.
This work was supported by Chinese Joint Seismological Science Foundation under the grants 92088 and 196098. 相似文献
998.
DKY95XHP5型地勘牙轮钻头采用了楔形硬质合金镶齿、滑动轴承密封润滑,储油和平衡补偿和新型专利喷嘴等先进结构,使用该钻头及配套无岩心钻进工艺,在中硬砂岩和灰岩中钻进,钻探台效提高,单位进尺成本降低。 相似文献
999.
1000.
利用建立人模拟旋喷装置,对喷浆提速进行了研究。模拟试验成果及初步分析表明,适当提高喷浆速度,不会影响成桩质量,在广州工地施工试验表明,钻孔孔口反浆后,中速喷浆,可节约水泥,而桩的承载力不变。 相似文献