Study on the sudden changes in ground tilt and earthquakes

Introduction Many observation facts, rock-rupture experimental results, and theoretical research achievements proved that the sudden changes in ground deformation are the most possible earthquake short-term precursors. The observed sudden changes in deformation that related to the earthquake preparation are here called the precursory. The sudden change is mainly characterized by the highly changing velocity and greatly accumulated deformation amplitude.     

The Isotopic Composition of Noble Gases in Gold Deposits and the Source of Ore- Forming Materials in the Region of North Hebei, China

1IntroductionOnthenorthernmarginoftheNorthChinaplatformislocatedoneofthemostimportantAu Ag polymetallicore concentratedzones,wherethereareavarietyoforetypes .Soithasbeenat tractingeverincreasingattentionofmanygeologists (PeiRongfuetal.,1 998;ShenBaofengetal.,1 994 ;LuSongnianetal.,1 997;HuShouxietal.,1 994 ;ChenYuchuan ,1 999;ZhaiYushengetal.,1 999) .Manyscholarspresentedtheirresearchresultsinvariousaspects.How ever ,thesourceofore formingmaterialshaslongbeenafocusofdiscussion .Studieso…     

潜水自然防护性能的评价及效果分析

本文以大量的水文地质勘探结果为依据,引用了水文地质参数:隔、透水层的厚度(A、B)和渗透系数(K_1、K_2)。对研究区非饱和带进行统计计算,求出该带的垂直自然防护性能指数。同时选择饱和带特征参数导水系数(T),计算出潜水自然防护性能总指数后,对潜水自然防护性能进行评价。     

冷原子荧光法直接测定海水中痕量汞

用冷原子荧光直接测定海水中的痕量汞,目前在我国还未正式使用.国内外普遍使用的是无焰原子吸收或冷原子吸收法进行直接分析或富集浓缩后进行分析[1,2].但富集法步骤麻烦、装置复杂、容使样品污染,且样品用量大,要消耗大量的试剂和分析时间.本文叙述了利用国产YYG-77型冷原子荧光测汞仪[3,4,5],改进了还原器,使用封闭进样,使整个体系在测量时处于封闭状态,消除了由于空气进入而产生的荧光猝灭;同时对不同的进样方式作了比较实验.通过大量实验,选择了最佳实验条件和适当的反应的体积,取样量改为50毫升,使本方法的检测限由原仪器的0.05微克/升降低到0.002微克/升;精密度为2-5%.每个样品的测定时间只需40-60秒.本方法适于天然海水中痕量汞的测定,也便于海上操作.     

The effect of unstable inertia-gravity wave on the occurrence and the development of typhoon and tropical cyclone

In this paper,the analysis of the occurrence and the development of typhoon and tropical cyclone is made with the unstable theory of wave. The result indicates that the primary wave is the unstable inertia-gravity wave in the process of the occurrence and the deveJopmant of typhoon and tropical cyclone: The existence of the deep moist layer and the heating by moisture condensation can impel and intensify the unstability of the wave and is favourable for the reduction of the wave energy dispersion, therefore, it is good for the formation and the development of typhoon and tropical cyclone, and also can slow down the wave speed. Besides, the condition that the change of the specific volume of the basic state with pressure is less than that of adiabatic state may also lead to the wave unstability, thus may have certain effect on the occurrence and the development of typhoon and tropical cyclone.     

循环流化床燃烧过程自适应双环选择控制系统

本文根据循环流化床燃烧过程的动态特性和现场运行经验 ,提出了 1种符合实际应用的自适应双环选择控制系统。该系统在床层温度不越限的情况下 ,以控制主蒸汽压力稳定为主要目标。当床层温度发生越限时 ,系统自动变换控制策略并调整床层温度恢复到正常 ,这种控制方式有效地减弱了主蒸汽压力与床层温度之间的耦合关系。该系统结构简单、实用 ,具有工程应用价值 ,现场运行收到较好的控制效果     

嫩江地区中晚加里东期区域变质岩系构造背景

按板块构造划分,嫩江地区位于兴蒙造山带东段兴安地块与松嫩地块交会部位,区内多期次的构造叠加作用强烈,是研究兴蒙造山带构造演化的关键地区之一。从研究区中晚加里东期区域变质岩系的区域地质背景着手,结合现有的区域地层和构造资料,对区内中晚加里东期区域变质岩系岩石学及地球化学特征、变质变形特征进行分析,通过野外地质产状和岩石共生组合的分析、变质作用及变质相的划分、构造环境判别等方法对区内中晚加里东期所经历的构造背景问题进行研究,认为研究区经历了弧后拉张→岛弧火山喷发沉积→弧后边缘海盆地伸展→弧后边缘盆地沉积的大地构造背景。区内中晚加里东期区域变质岩系的研究,对于重建嫩江地区加里东期构造背景具有重要意义。     

Experimental study on damage failure mechanical characteristics and crack evolution of water-bearing surrounding rock

Water plays an important role in the mechanical properties of roadway surrounding rocks and poses a great threat to their stability. To study the damage and failure characteristics, and the fracture development laws of surrounding rock, a uniaxial compression test for prefabricated fractures in water-bearing surrounding rock was carried out. Results indicate that water-bearing prefabricated fracture specimens are in better development condition after failure. In water-bearing specimens, the propagation direction is more complex. There are more secondary fissures, and the fracture strength is significantly lower than in dry specimens. When immersed in water, the interior structure of surrounding rock is weakened and softened; thus, the intensity is reduced, and the development and propagation of fractures is promoted. For larger angles of the prefabricated fractures, the compression failure of surrounding rock changes into shear failure. As the angles approach 90°, the shear failure again prevails. Therefore, the strength of the surrounding rock firstly decreases and then increases. A new ultimate stress strength model is developed for fractures caused by shear slip failure in water-bearing surrounding rock. The model results are consistent with the experimental results, and the validity of the model is verified. These results are helpful for deeply understanding the failure process of water-bearing surrounding rock with prefabricated fractures. The proposed model could be used for the evaluation of water-bearing surrounding rock stability in coal mines, as well as dynamic risk monitoring.     

The Eocene corundum-bearing rocks in the Gangdese arc,south Tibet:Implications for tectonic evolution of the Himalayan orogen

The genesis of Liangguo corundum deposit in the southern Gangdese magmatic arc, east-central Himalaya, remains unknown. The present study shows that the corundum-bearing rocks occur as lenses with variable sizes in the Eocene gabbro that intruded into marble. These corundum-bearing rocks have highly variable mineral assemblage and mode. The corundum-rich rocks are characterized by containing abundant corundum, and minor spinel, ilmenite and magnetite, whereas the corundum-poor and corundum-free rocks have variable contents of spinel, plagioclase, sillimanite, cordierite, ilmenite and magnetite. The host gabbro shows variable degrees of hydration and carbonization. The corundum grains are mostly black, and rarely blue, and have minor Fe O and TiO_2. The spinel is hercynite, with high Fe O and low Mg O contents. The corundum-bearing rocks have variable but high Al_2O_3, FeO and TiO_2, and low SiO_2 contents. Inherited magmatic and altered zircons of the corundum-bearing rocks have similar U e Pb ages(~47 Ma) to the magmatic zircons of the host gabbro, indicating corundum-bearing rock formation immediately after the gabbro intrusion. We considered that emplacement of gabbro induced the contact metamorphism of the country-rock marble and the formation of silica-poor fluid. The channeled infiltration of generated fluid in turn resulted in the hydrothermal metasomatism of the gabbro, which characterized by considerable loss of Si from the gabbro and strong residual enrichment of Al. The metasomatic alteration probably formed under Pe T conditions of ~2.2 -2.8 kbar and ~650 -700℃. We speculate that SiO_2, CaO and Na_2O were mobile, and Al_2O_3, FeO, TiO_2 and high field strength elements remained immobile during the metasomatic process of the gabbro. The Liangguo corundum deposit, together with metamorphic corundum deposits in Central and Southeast Asia, were related to the Cenozoic Himalayan orogeny, and therefore are plate tectonic indicators.     

An anionic biopolymer γ-polyglutamate enhanced the microbially induced carbonate precipitation for soil improvement: mechanical behaviors and underlying mechanism

The use of biopolymer to improve the performance of microbially induced carbonate precipitation (MICP)-treated sands is a novel and eco-friendly concept. This work found an anionic biopolymer, γ-polyglutamate (γ-PGA), could significantly improve the performance of MICP-treated sands. Comparing the control with absence of γ-PGA, the concentration of 0.1–9 g/L γ-PGA increased the compressive strength of MICP-treated sands by 1.54–3.96 times and significantly reduced the brittleness. The MICP process analysis and microstructural detection demonstrated that γ-PGA in the specimens provided many nucleation sites and templates for calcite generation, partially kept the bacterial urease activity by replacement of the bacteria as nucleation sites, thereby improving the calcite generation. The γ-PGA also cemented sand grains with calcite through the hydrogen bond-type intermolecular interactions. Both the calcite generation and the hydrogen bond-type intermolecular interactions by γ-PGA played vital roles in enhancing MICP for soil improvement. Additionally, γ-PGA, as a viscoelastic admixture between the crystals and sand grains, effectively dissipated the energy of stress and thus reduced the brittleness of MICP-treated sands. This is the first report on the application of anionic biopolymer to MICP technology. It provides a novel concept in promoting the efficiency and sustainability of MICP.