大姚-姚安地区强震孕震机理--NW向褶皱节理的构造强化与活动

以21世纪初滇中大姚—姚安一带接连发生的4次Ms6.0~6.5级强震为例,通过分析该地区构造类型及其演化历史,结合川滇块体的现今运动特征和构造应力场,提出滇中构造区运动模型和特殊的孕震模式,探讨褶皱节理与地震活动的关系。研究表明,这些地震序列均有规律地沿北西方向展布,具有高度一致的沿北西向节理面右旋走滑的力学破裂机制。该地区断裂不发育,而是以北西向中生代褶皱构造为主。野外调查发现,该地区广泛发育与褶皱伴生的北西向纵向节理及北东向横向节理,前者较后者更为发育。这些节理密集成带,呈不等间距排列,带宽30~50 m,带内节理密度20~30条/m。节理面上发育有方解石脉和辉长岩脉,同时发育挤压片理化带、新鲜的水平擦痕和松软的断层泥,说明这些节理不仅与深部地壳有关联,而且近期有着新活动迹象。分析认为,在滇中块体南南东运动的背景下,这些地震是在现今北北西向挤压应力场作用下,北西向纵向节理发生构造强化、贯通、破裂的过程中产生的。"活节理"与活动断裂、活动褶皱等构造一样,是地球上广泛存在的活动构造之一。在特殊的构造环境和特定的构造应力场作用下,节理构造会演变为一种构造强化带或活化带,进而成为一种特殊的孕震构造。

矿井地质构造强化现象特征及应用

本文结合煤矿井下多年工作实践，阐述了矿井断裂地质构造形成过程中产生的各种强化现象特征、特点，以及如何应用这些强化现象特征解决生产中所碰到的断层构造问题。

盆地陆源碎屑沉积物对源区构造背景的指示意义

盆地陆源碎屑沉积物对源区构造演化有重要的指示作用 ,目前利用盆地陆源碎屑沉积物示踪源区 ,反演源区构造演化的方法很多 ,包括沉积碎屑组分分析方法、地球化学分析方法及同位素年代学方法等。结合实例分析 ,简要介绍了这几种方法目前的研究进展及存在问题。由于盆地沉积碎屑组分、副 (重 )矿物及地球化学方法仅能够提供源区物质组成方面的信息 ,因此在应用上有很大的局限性。而同位素年代学方法则可以提供源区年龄组成方面的信息 ,锆石U Pb及FT年代学的结合 ,是一种新的突破。结合区域构造背景 ,有选择地进行多种方法综合分析应是行之有效的手段。

KT形RHS加强节点承载力试验研究与数值分析

结合呼和浩特火车东站站房钢结构工程,针对其高频度使用的矩管KT形RHS节点,从受力、工艺和经济性出发,综合阐述了节点局部构造加强方式的工艺力学性能差异。采用模型试验和数值计算结合的方法,分析弦杆外套和弦杆内加劲两种强化方式的静力力学行为差异,数值分析采用引入Low-Speed Dynamics Damping Factor的非线性N-R方法,考虑材料屈服与破裂失效,基于Adina的隐式算法模拟模型的显式破坏特征。对节点进行抽象简化处理,综合考虑工艺力学性能,设计3组不同构造的KT形RHS节点,进行1∶2缩尺比例静力加载试验。分析两种强化方式对其质量控制、承载能力、破坏形态的影响,并与无任何加强措施的构件结构进行对比,结果表明,套管强化方式能够明显提高节点的承载能力和刚度,工艺性较好,可结合实际工程条件,提供节点强化设计参考。

Influencing factors analysis of hard limestone reformation and strength weakening under acidic effect

Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way to control the hard limestone roof.In this study,the effects of various factors on the reaction characteristics and mechanical properties of limestone were analyzed.The results show that the acid with stronger hydrogen production capacity after ionization(pK_(a)<0)has more prominent damage to the mineral grains of limestone.When pKa increases from−8.00 to 15.70,uniaxial compressive strength and elastic modulus of limestone increase by 117.22%and 75.98%.The influence of acid concentration is manifested in the dissolution behavior of mineral crystals,the crystal defects caused by large-scale acid action will lead to the deterioration of limestone strength,and the strength after 15%concentration reformation can be reduced by 59.42%.The effect of acidification time on limestone has stages and is the most obvious in the initial metathesis reaction stage(within 60 min).The key to the strength damage of acidified limestone is the participation of hydrogen ions in the reaction system.Based on the analytic hierarchy process method,the influence weights of acid type,acid concentration and acidification time on strength are 24.30%,59.54% and 16.16%,respectively.The research results provide theoretical support for the acidification control of hard limestone roofs in coal mines.

Mechanical performance of the mixed post-installed connection in low-strength concrete

Due to inadequate bearing capacity of the chemically-planted steel bar in low-strength concrete, a new mixed post-installed connection is proposed using small diameter anchoring steel bars and grouting materials together to anchor the main steel bar. To investigate the feasibility of the proposed post-installed connections, a series of pull-out tests with different anchors were conducted for comparison,including fully adhesive anchors, partially adhesive anchors,grouting material anchoring connection and the new mixed post-installed connection. The experimental results of the single steel bar pull-out test show that the mixed post-installed connection can effectively enhance the bearing capacity of post-installed steel bars in low-strength concrete. The bearing capacity is increased by nearly two times with no cone-type concrete failure compared with the fully adhesive anchor. The results show that adopting the new mixed post-installed connection can ensure that joint performance meets the requirements if the space dimension is available.

The influence of intensity and properties of tectonic stress on the process of coalification

Through the research on stress metamorphism character of the II1 coal seam in Ludian gliding structure, the stress effecting factors of metamorphism and hydrocarbon generation process of tectonic coal were studied. It is shown that different tectonic stress has different coal evolution effects. Compared with tensional stress, compressive stress, which has apparent anisotropic characteristics, has greater stimulative effect against the increase of coal metamorphic degree, the abscission of functional group and side chains of basic structural unit, and the formation of gas primarily composed of methane.

Discovery of the Indosinian aluminum A-type granite in Zhejiang Province and its geological significance

Zircon LA-ICP-MS U-Pb dating of the Jingju syenogranites in the southwestern part of Zhejiang Province shows that these rocks were crystallized in the Late Triassic at 215±2 Ma, rather than in the Cretaceous as previously proposed. The Jingju sy- enogranites are characterized by relatively high K2O and FeO＊, and low MgO. They have high concentrations of large ion lithophile elements （LIL） and LREE, such as K, Th, La, and Ce, but are depleted in high field strength elements （HFSE） such as Nb, Ta, and Ti. Their 104Ga/A1 ratios and （Zr＋Nb＋Ce＋Y） contents are also high. These characteristics are similar to those of A-type granites. The syenogranites have high Isr （0.7179-0.7203）, low eNa（t） （from --14.2 to --13.2）, and relatively old T2DM ages, similar to those of the ancient metamorphic basement in the Cathaysia Block. It is suggested that the Jingju syenogranites were formed by partial melting of the Cathaysia basement rocks during tectonic extension. This identification of Indosinian A-type granite in Jingju has significant implications for understanding the early Mesozoic tectonic evolution of South China.