预应力锚索复合土钉支护的现场测试研究

结合北京熊猫环岛地铁车站深基坑支护工程,通过对预应力锚索与土钉联合使用条件下土钉轴力随时间变化、土钉轴力沿长度的分布、土钉轴力最大值的分布、锚索预应力的变化等现场测试及分析,从力学机制上研究了预应力锚索复合土钉的工作机理,研究表明:(1)土钉受力具有时间效应及开挖效应;(2)土钉轴力形成和空间分布与基坑潜在滑动趋势有关;(3)预应力锚索对作用范围内土钉轴力空间分布有一定影响;(4)预应力锚索可减小坡体位移,使得各土钉轴力相对减小,改善坡体应力状态;(5)工作状态下,土钉和预应力锚索的受力状态变化相互影响较小,各自发挥作用。     

大洋海底扩张图蛛网裂缝的扁壳力学模式

在考虑半径为10~3公里数量级的全球海洋岩石圈时,必须考虑地球的弯曲效应,当作弹性地基上的薄扁球壳。若忽略曲率,将产生各向异性和不均匀性。本文还考虑了地热对岩石圈的作用,得出洋底蛛网状裂缝的力学表达式。     

Experimental study on the rheological properties of polycrystalline solid nitrogen and methane: Implications for tectonic processes on Triton

To investigate the evolution of any processes on planetary surfaces in the outer Solar System, the rheological properties of non-water ices were studied by means of a sound velocity measurement system and a uniaxial deformation apparatus. A pulse transmission method was used to obtain longitudinal (V_p) and transverse (V_s) wave velocities through solid nitrogen and methane at temperatures ranging from 5 to 64 K and from 5 to 90 K, respectively. The measured velocities confirmed that the solid methane and solid nitrogen samples were non-porous polycrystalline samples without any cracks and bubbles inside. Compression tests at constant strain-rate were performed for solid nitrogen and methane at temperatures of 5-56 K and 5-77 K, respectively, at strain-rates of 10⁻⁴-10⁻² s⁻¹. Both brittle and ductile behavior was observed for solid nitrogen and methane under these conditions. The maximum strength of solid nitrogen was observed to be 9 MPa in the brittle failure mode, and that of solid methane was 10 MPa. These low strengths cannot support cantaloupe structures with the topographic undulation larger than several kilometers found on Triton’s surface, suggesting that other materials such as H₂O ice could underlay solid methane and nitrogen and support these structures.     

Rate-dependent strength of porous ice–silica mixtures and its implications for the shape of small to middle-sized icy satellites

Porosity is one of the most important physical properties in the rheology of small icy satellites composed of ice–silicate mixtures. Deformation experiments involving ice and 1 μm silica bead mixtures were conducted to clarify the effect of porosity on the flow law of ice–silica mixtures. Mixtures with silica mass contents of 0, 30, and 50 wt.% were used for the experiments, and the porosity was changed from 0% to 25% in each mixture. The temperature ranged from −10 to −20 °C, and the strain rate was changed from 1.2 × 10⁻⁶ to 4.2 × 10⁻⁴ s⁻¹. As a result, it was found that the ice–silica mixtures deformed plastically, and that the relationship between the maximum stress, σ_max, on the stress–strain curve and the applied strain rate, , could be described by the following flow law: . The mixture became softer as the porosity or silica mass content increased, and the stress exponent n and activation energy Q were independent of porosity, depending only on the silica mass content. Furthermore, the parameter A₀ could be written as A₀ = B(1 − ?)^−α, where ? is the porosity. The constants B and α also depended only on the silica mass content, and they increased with the increase in this content. The Maxwell relaxation time was calculated in order to estimate the conditions for topographic relaxation of icy satellites, and it was found that topographic relaxation occurred at temperatures higher than 160 K in the case of icy satellites with mean radii of 200 km.     

西安地裂成因力学问题初探

给出了西安地裂的构造模型,并用断裂力学原理分析了地裂的形成与扩展过程,准定量地比较了抽取地下水所引起的地面不均匀沉降以及构造运动所产生的地裂位移在地裂总位移中所占的比例。提出了构造对地裂发育不但有静态控制作用而且有动态控制作用。认为西安地裂是构造地裂,而西安地裂的致灾作用主要是由过量抽取地下承压水所引起的。     

桩基础在无限层地基中的轴向地震反应分析

本文对无限层弹性地基中单桩基础通过特性分析建立了合理的软科学模型，按分层弹性地基土模型对桩进行动力分析，给出了桩基础轴向自振特性及在竖向地震载荷与动力载荷作用了强迫反应的解析解，文中的解析公式为无限层弹性地基中的单桩基础轴向地震反应分析提供了一种新的解析方法。     

大华北新构造运动和地震活动“成片迁移”的成因探讨

基于板块间的作用及有关物理参数,分别组构了大华北第Ⅲ（1484-1739年）、第Ⅳ（1815年至今）地震活动期的动力边界和厚度非均匀的“薄板”模型,采用有限元法,并根据地壳屈曲的研究,作了屈曲变形计算.所得屈曲图象与大华北新生代隆起、凹陷分布的基本特征一致,也与近30年来大华北垂直形变速率的分布特怔吻合.不同期高变形梯度区不同,7级以上地震均分布在这种区内.由此得出了新构造运动和地震“成片迁移”的力学机制.     

硼酸对硫氧镁水泥力学性能的影响

硫酸浸出法制备硼酸的废弃母液经过浮选法分离产生的硫酸镁中通常含有硼酸等杂质,为了研究硼酸对硫氧镁水泥凝结硬化及力学性能的影响,以改性硫氧镁水泥(MOS)为基础体系,测试了硼酸含量对硫氧镁水泥凝结时间、抗压和抗折强度的影响,讨论了硼酸对硫氧镁水泥抗水性、水化产物及微观形貌的影响。结果表明:硫氧镁水泥的凝结时间随硼酸含量的增加而延长;硼酸可以明显降低硫氧镁水泥的早期强度,对后期强度的降低作用不及早期明显;试件浸水28 d后,较高含量的硼酸提高了试件抗压强度的软化系数,而降低了抗折强度的软化系数,因此硫酸镁中硼酸含量不应超过0.7%;硫酸镁中硼酸含量不影响硫氧镁水泥水化产物的组成,但降低了水化产物的结晶度并改变其显微结构。     

Inversion of calcite twin data,paleostress reconstruction and multiphase weak deformation in cratonic interior – Evidence from the Proterozoic Cuddapah basin,India

Paleostress orientations from mechanically twinned calcite in carbonate rocks and veins in the neighborhood of large faults were investigated to comment on the nature of weak upper crustal stresses affecting sedimentary successions within the Proterozoic Cuddapah basin, India. Application of Turner's P–B–T method and Spang's Numerical dynamic analysis on Cuddapah samples provided paleostress orientations comparable to those derived from fault-slip inversion. Results from the neighborhood of E–W faults cutting through the Paleoproterozoic Papaghni and Chitravati groups and the Neoproterozoic Kurnool Group in the western Cuddapah basin, reveal existence of multiple deformation events − (1) NE–SW σ₃ in strike-slip to extensional regime along with an additional event having NW–SE σ_3, for lower Cuddapah samples; (2) compressional/transpressional event with ESE–WNW or NNE–SSW σ₁ mainly from younger Kurnool samples.Integrating results from calcite twin data inversion, fault-slip analysis and regional geology we propose that late Mesoproterozoic crustal extension led to initial opening of the Kurnool sub-basin, subsequently influenced by weak compressional deformation. The dynamic analysis of calcite twins thus constrains the stress regimes influencing basin initiation in the southern Indian cratonic interior and subsequent basin inversion in relation to craton margin mobile belts and plausible global tectonic events in the Proterozoic.     

震击高压变质作用:观察与启示

近六十多年来,关于造山带高压变质作用发生的原因一直存在争议。当前的主流观点认为高压变质岩形成于俯冲带深部以后折返到地壳。虽然早就认识到蓝片岩相变质作用总是与逆冲断裂相伴并且变质压力朝着冲断面增高,而标志地震的榴辉岩相假玄武玻璃也已经发现了二十多年,但是一般认为断裂或剪切带的作用只是引进流体促进深部岩石的变质反应。几年前,苏文辉等人(Su et al.,2006)通过实验演示了石英经过非晶化可以在柯石英稳定的压力下迅速转变为柯石英,提出无需深俯冲,浅源地震即可形成柯石英。本文介绍笔者等人对中国苏鲁超高压变质带仰口榴辉岩的部分工作结果,从地质观察角度为这一论点提供证据。例如,粒间柯石英仅出现在榴辉岩相角砾岩的角砾而非胶结物中,它必须在相当于地震的时间尺度快速降压冷却才能得以保存。变辉长岩中的榴辉岩相碎裂岩脉也记录了应力导致的瞬时高压和高温。角砾岩和碎裂岩中包含大量高压矿物的石榴石和针状蓝晶石以及局部出现的"显微花岗岩"都是类似地震熔体淬火的结果。它们指示震后高压矿物没有再生长。而如果地震发生在深部,流体浸入后矿物应当在高压下持续结晶,从而消除淬火结构。碎裂岩脉中星散的铬铁矿微粒极可能是附近超镁铁岩通过断裂迸溅进入基性岩的,是地震中不同岩石机械混合的证据;环绕它们的富铬榴辉岩矿物记录着一次无可争议的瞬时高压结晶事件。碎裂岩脉相对围岩更缺乏流体的事实反映应力而非流体在高压相变中的关键作用。榴辉岩相角砾岩和碎裂岩脉形成的时间尺度太小,来不及完成俯冲和折返过程。它们更可能是辉长岩在地壳原地因地震波引起的高压发生了榴辉岩化作用。目前的地震力学模型不能导出高压相变所需要的压力,只是因为建立模型时没有考虑涉及高压相变的地震。需要强调的是,假说或理论需要观察事实的检验而不是相反。已有资料显示,瞬时熔融和非晶化可能是震击高压相变的路径。