地层场地效应对东河口地震滑坡发生影响研究

以汶川极震区青川东河口地震滑坡为典型实例,首先从滑坡地脉动现场测试的频谱特征曲线分析可得,卓越频率在1~3Hz范围内,且NS向的谱比值最大。其次,通过对东河口滑坡单一结构、二元结构两种弹性模型输入不同中心频率0.5Hz^4Hz的Ricker子波,发现二元结构的PGA放大系数普遍大于单一结构,同时中心频率较低时,滑坡PGA放大系数分布范围较广,相反,较高中心频率的PGA放大系数仅集中在坡顶和两侧山脊处,表明:中心频率高低对于PGA放大系数影响范围也不同。最后,对东河口地震滑坡弹塑性模型输入汶川地震绵竹清平台站加速度记录,根据监测点残余变形,认为滑坡破坏发生在6.5s处,并结合输入地震波频率在此时刻出现较高傅立叶谱值,表明东河口地震滑坡的发生是由高频谱值输入地震波触发。本研究有助于从地层场地效应角度理解斜坡动力失稳过程。

软弱土地基处理方案比选论证的分析研究

以实际工程为例,分析了软弱土地基处理的方法,并根据实际工程的特点,选择了两种适合于本工程软弱土地基处理的方法进行技术经济分析,从而使软弱土地基处理的造价、工期等达到最优,为类似工程处理提供参考。

工程质量检测站岩土工程评价及基础方案分析

阐述了场地的地层情况及工程地质条件的评价,能够准确为设计部门提供可靠的设计参数,对地基基础方案进行了分析,提出经济合理的地基基础方案。

岩土工程评价及基础方案分析

本文以成都市某安置楼地基为研究对象,对场地的地层情况及工程地质条件进行了评价,对拟建场地的稳定性、地震效应、地基持力层等做出了分析与评价,并提出了地基基础方案的分析与建议。

岩土工程勘察数字化技术和实现

岩土勘察是工程建设的前提,应先通过岩土勘察明确建筑物所处环境的地质条件,才能精准的制定相应的建设方案和地基处理措施。传统的勘察是采用测量仪器、勘察设备等进行,不仅误差较大而且很难全面了解岩土工程地质条件的土层状态。基于此本文提出岩土工程勘察的数字化技术,通过地理信息系统和岩土工程建模实现场地区域数字化和场地地层的数字化。岩土勘察的数字化处理能够准确而全面的对勘察范围的岩土信息进行模拟和呈现,方便设计者和建筑者对岩土信息进行整体了解,便于施工位置的确定和岩土设计方案的制定。

Study on the Recent Tectonic Stress Field in the Yunnan Region

In this paper, using focal mechanism solutions of moderate-strong earthquakes in Yunnan and its adjacent areas, and based on the statistical analysis of the parameters of focal mechanism solutions, we discussed in detail the earthquake fault types and the characteristics of the modern tectonic stress field in the Yunnan region. The results show that most moderate-strong earthquakes occurring in the Yunnan region are of the strike-slip type, amounting to 80% of the total. Normal faulting and normal with strike-slip and reverse and reverse with strike-slip earthquakes is almost equivalent in proportion, about 8% each. The tectonic stress field of the Yunnan region is near-horizontal, and the dips of earthquake fault planes are large. There are three main dynamic sources acting on the Yunnan region: one is the NE, NNE and NNW-directed acting force from Myanmar, Laos and Vietnam; the second is the SE-SSE directed force from the Sichuan and Sichuan-Yunnan rhombus block and the third is the NW-NNW directed force from the South China block. These three acting forces have controlled the faulting behavior of the main faults and the characteristics of strong earthquake activity of Yunnan and its adjacent regions.

The Northern End of the Xiannvshan Fault at the Three Gorges Area

The Xiannvshan fault zone, lying along the western margin of the Huangling anticline, is one of the most important fault zones in the Three Gorges reservoir area. The fault experienced strong activity during the Cenozoic Era. The question of whether the fault zone goes through the Yangtze River has been one of the key problems faced in previous studies as it has a significant influence upon the assessment of geological hazards and earthquake stability in the reservoir area. Based on tectonic and geomorphic observations along the fault zone between the Baixianchi village in Changyang county and Huangkou village in Zigui town, together with the comparisons between the geology in Guizhou and Quyuan town in the north bank of the Yangtze River and the Xiannvshan fault zone, it is suggested that the north end of this fault zone is located around Huangkou village and does not go through the Yangtze rivers northward. The evidence is as follows: ① On the basis of field data collection, it is found that the Xiannvshan Fault zone, which stretches 80km, underwent thrust movement in the Cenozoic period, resulting in ravines and fault scarps, topographically. Whereas, on the northern bank of the Yangtze River, faults are rarely found, and most of the faults are developed in the Jurassic strata,without topographical effects. Therefore, the Xiannvshan Fault zone has not stretched to the north bank of the Yangtze River. ② The fault gouge and tectonite zone were found developed on the Xiannvshan Fault zone at Baixianchi village, but only a tectonite zone was found at Zhouping village. There are also some branch faults close to the northern end of the fault zone. So, the activity of the fault zone weakened from south to north in Cenozoic. The fault zone extends northward and dies out at Huangkou. It doesn't stretch forward any longer as indicated by continuous strata, sparse joints, and small folds, etc.

Statistical Analysis of the Dynamic Parameters of Silty Clay in the Beijing Area

Soil dynamic parameters,including dynamic shear modulus ratio and damping ratio,have important effects on the results of layered soil earthquake response. In this paper,the mean parameter values of silty clay in different depths are obtained after statistical analysis of the experimental soil dynamic data from 20 recent site seismic safety evaluation reports in the Beijing area. Furthermore,based on two typical engineering sites,the influence of four different soil dynamic parameters,the statistic mean values,experimental values, values recommended by Yuan Xiaoming,and the values recommended in the code for seismic safety evaluation of engineering sites( DB001-94) are analyzed. The result shows that mean statistical values are applicable to seismic safety evaluation work in the Beijing area,especially for some inter-layered silty clays whose undisturbed soil samples are hard to obtain.

New understanding achieved from 2 years of Chinese ionospheric investigations

In the mainland of China, the number of ionospheric research groups is more than 10. Around 110 articles related to ionospheric physics have been published during 2014–2015. In this annual national report of the Committee on Space Research(COSPAR), we will outline some recent progresses in ionospheric studies conducted by the Chinese mainland scientists in the past 2 years. These investigations cover(1) the ionosphere responses to geomagnetic activities;(2) ionospheric climatology and structures;(3) couplings between the ionosphere, plasmasphere and lower atmosphere, and possible seismic signatures in the ionosphere;(4) ionospheric irregularities and scintillation;(5) ionospheric models, data assimilation and simulations;(6) ionospheric dynamics and electrodynamics;(7) progresses in the observation methodology and technique; and(8) planetary ionospheres. Such investigations will strengthen our ability to monitor the ionosphere,provide a better understanding of the ionospheric states and the underlying fundamental processes, and improve the ionospheric modeling, forecasting, and related applications.