湖北大冶铁山矿区构造的岩组分析

本文采用了方解石光轴优选方位、e双晶C—T图法、以及两种用e双晶页理估算应力大小的动力学方法,对鄂东大冶铁山矿区的大理岩进行了岩组学的研究,根据所得资料的分析及相互印证,得出了若干结论。是一次运用岩组分析配合地区构造研究的尝试。     

温度和含冰量对冻结土石混合体力学特性的影响

冻结土石混合体是一种力学特性极为复杂的岩土材料,其力学特性对温度和含冰量等因素非常敏感。然而到目前为止,对于其力学行为随温度、含冰量及法向压力等的变化特征仍然缺乏足够的了解。本文开展了一系列的冻结土石混合体的直剪试验,研究了温度、含冰量及法向压力对冻结土石混合体剪切特性的影响。结果显示温度、含冰量及法向压力对冻结土石混合体的剪切行为都有重要影响。在其他条件相同时,冻结土石混合体的抗剪强度随着温度的下降呈指数形式增长。当温度高于-5℃时,抗剪强度增加很快,而当温度低于-5℃时,抗剪强度仅有微小增加。在-5℃时,冻结土石混合体的抗剪强度随着含冰量的增加先增加后减少。抗剪强度最大值出现在含冰量在11%左右。冻结土石混合体的粘聚力随着含冰量的增加先迅速增加,在含冰量大于11%以后,粘聚力又有微小下降,而内摩擦角随着含冰量的增加缓慢减小。冻结土石混合体的抗剪强度随着法向应力的增加而增加,但在高法向应力下,其塑性增强。     

大气热力强迫和动力强迫的调配及平均经圈环流的仿真模拟

通过研究平均经围环流（ＭＭＣ）及其所受的内外强迫作用的相互配置，指出对ＭＭＣ的热力和动力强迫满足确定的调配率。这一调配率受大气内在的斜压性、静力稳定度及绝对涡度制约。利用辐射加热和凝结加热参数化方案，结合欧洲中期天气预报中心（ＥＣＭＷＦ）的分析资料，对１月份平均经围环流进行数值仿真模拟。结果表明，热带对流加热可以形成双层Ｈａｄｌｅｙ环流结构；涡动动量输送对双Ｈａｄｌｅｙ环流的形成也有一定影响。中高纬度的ＭＭＣ则主要由外动量强迫及大气的动量和热量输送特征决定。     

纤维加筋土工程性质研究进展

纤维加筋是一种新型的土体改良技术,是指将分散的纤维丝均匀掺入土体中,达到提高土体的工程力学性能的目的。本文根据国内外近20a来在该领域取得的成果,着重对纤维加筋材料、纤维加筋土的工程性质及加筋机理等方面的研究进展进行了介绍。在纤维加筋材料方面,主要有人工合成纤维和自然纤维两种; 在纤维加筋土工程性质方面,纤维加筋能有效提高土体的抗剪、抗压、抗拉强度和承载力,增加土体的破坏韧性和渗透性,降低膨胀土的胀缩性和裂隙发育程度; 在纤维加筋机理方面,目前主要认为纤维的加筋效果主要取决于纤维-土界面的力学作用,即界面黏聚力和摩擦力。最后,针对目前纤维加筋土的研究不足,提出了今后该领域的研究重点和方向,主要包括: 开发简单可行的纤维土施工器具和工艺、开发更专业的纤维产品和降低纤维成本、开展大尺度模型试验和现场试验、纤维-土界面作用机理研究、纤维加筋土的破坏和失效机理研究、纤维加筋土的力学模型及计算理论研究、纤维加筋土的动力学特性研究等。     

How tightly does calcite e-twin constrain stress?

Mechanical twinning along calcite e-planes has been used for paleostress analyses. Since the twinning has a critical resolved shear stress at ∼10 MPa, not only principal stress axes but also differential stress can be determined from the twins. In this article, five-dimensional stress space used in plasticity theory was introduced to describe the yield loci of calcite e-twinning. The constraints to paleostress from twin and untwin data and from calcite grains twinned on 0, 1, 2 and 3 e-planes were quantified by using their information contents, which were defined in the stress space. The orientations of twinned and untwinned e-planes are known to constrain not only stress axes but also differential stress, D, but they loose the resolution of D if the twin lamellae were formed at D greater than 50–100 MPa. On the other hand, it is difficult to observe twin lamellae subparallel to a thin section. The stochastic modeling of this effect showed that 20–25% of twin lamellae can be overlooked. The degradation of the constraints by this sampling bias can be serious especially for the determination of D.     

Micro-and submicrostructural evidence for high-temperature brittle-ductile transition deformation of hornblende: Case study of high-grade mylonites from Diancangshan, western Yunnan

OM (optical microscope)/TEM (transmission electron microscope) micro- and submicrostructural analysis of hornblende rocks sheared at high temperatures from the Diancangshan area, western Yunnan reveals evidence for deformation in the brittle-ductile transition of hornblende at middle crustal level (about 637℃ and 0.653 GPa) and mechanisms of deformation in the transitional regime are further discussed. Sheared hornblende rocks at middle crustal level have typical mylonitic microstructures, shown by coarse porphyroclasts and fine matrix grains. Different mineral phases in the rocks show distinct deformation characteristics. Hornblende and feldspar grains are intensely deformed with ob- vious grainsize reduction, but quartz grains are recrystallized dominantly by grain growth. Hornblende grains show typical brittle-ductile transition nature. Initial crystallographic orientations of porphyro- clasts have strong effects on the behavior of grains during deformation. There are mainly two types of porphyroclasts, type I "hard" porphyroclasts and type II "soft" porphyroclasts, with [001] perpendicular and parallel to external shear stresses respectively. "Hard" porphyroclasts generally occur as compe- tent grains that are rarely deformed or sometimes deformed by fracturing and dislocation tangling. "Soft" porphyroclasts are highly deformed primarily by dislocation tangling (as shown in the cores of the porphyroclasts), but twinning, dislocation glide and climb probably due to hydrolytic weakening also contribute to dynamic recrystallization of the porphyroclasts into fine grains in the matrix. The micro- and submicrostructures of the two types of porphyroclasts and fine-grained matrix provide powerful evidence for the behavior of brittle-ductile transition of hornblende grains. It is concluded that twinning nucleation is one of the most important processes that operate during dynamic recrystalliza- tion of hornblende crystals at the brittle-ductile transition. (100) [001] twin gliding and dislocation creep (dislocation glide and climb) are mutually enhanced during twinning nucleation. As a newly discovered mechanism of dynamic recrystallization, it may have played more important roles than ever recognized during dynamic recrystallization of crystals with twins in the brittle-ductile transition.     

不同类型氢氧化镁阻燃剂填充聚丙烯（PP）复合材料力学性能研究

研究了普通氢氧化镁(MH)、六角片状MH和硬脂酸改性MH分别填充聚丙烯(PP)复合材料的性能。用FTIR、SEM和TG对上述3种类型MH及其复合材料的结构和形貌进行了分析。试验结果表明:相比普通MH,六角片状MH和硬脂酸改性后的MH有效降低了表面极性,大大降低了对复合材料的力学性能的影响,显著提高了复合材料的热稳定性;4%SA改性MH比6%SA改性MH填充PP,界面相容性好,对复合材料力学性能的影响小。硬脂酸湿法表面处理氢氧化镁改性的最佳条件为:硬脂酸用量4%,处理温度85~90℃,处理时间60 min,料浆浓度10%。     

关于孔隙相互孤立饱和土体弹性模量的讨论

对孔隙相互孤立饱和土体的弹性力学模型的部分观点进行了讨论。按Carroll的力学响应理论重新推导了此类土体的弹性本构关系和体积模量表达式。认为在准静态(很低频率)的波动问题中孔隙流体与固体骨架的相对运动为零,土体渗透系数为零或流体粘性为无穷大的条件是等价的。在此条件下没有必要区分孔隙是否连通,它们遵循相同的规律,而且其土体弹性体积模量的结果与Biot-Geertsma理论的无排水准静态的弹性体积模量相同。     

循环剪切荷载作用下软土的力学性状研究

利用从现场取得的原状土样,通过室内动三轴试验对循环荷载作用下的变形、孔压和强度特性进行研究。试验研究主要考虑了周围固结压力、循环剪切应力比、荷载频率和循环次数等因素的影响。研究表明,在循环荷载作用下,孔隙水压力和轴向应变均是一个波动上升的过程。当循环应力比增大时,动孔隙水压力变化幅值显著增加,而残余孔压也较大。同时,孔隙水压力值也随着周围压力的增大而明显增大。当作用荷载频率比较大时,需要更多的循环次数才能达到小频率作用荷载能达到的孔隙水压力值。但是,随着循环荷载作用次数的增加,频率对孔隙水压力的影响有减小的趋势。     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).