岩浆驱动破裂的形态研究

轴地壳岩浆房是活动扩张中心海洋地壳结构的一个重要组成部分，轴地壳岩浆房通过深部岩浆源的补充，内部岩浆的同化熔融、结晶分异等岩浆房过程，其中的岩浆会破裂上覆的岩石层形成岩浆破裂，并沿岩浆破裂继续向上迁移。本文建立了岩浆迁移的层流模型，从理论上对岩浆迁移问题进行了探讨，并将遗传算法引入到该问题中来，用遗传算法求解了描述岩浆驱动破裂传播的积分方程。如果假设岩浆破裂在远离破裂末梢处的权限宽度为1M，则靠近末梢，破裂的宽度逐渐加大，在末梢处宽度为2m左右。并根据文献对岩浆流体的一些观测参数计算得出，岩浆破裂权限宽度不会很大，一般在1m左右的量级。     

曲边冰洲石的发现及其矿床成因的探讨

在各类型冰洲石矿床中发现了大量的冰洲石弯晶，通过冰洲石矿床野外考察的归纳总结，联系到晶体生长和材料力学的有关知识，提出冰州石矿床的成因极可能是原矿床中方解石受到的构造运动强烈影响后，在长期的水淋滤改造作用下发生冰洲石化，并由此而形成冰洲石矿床。     

Extreme value theory based on the r largest annual events: a robust approach

In Smith (1986, J. Hydrol. 86, 27–43), a family of statistical distributions and estimators for extreme values based on a fixed number r > = 1 of the largest annual events are presented. The method of estimation was numerical maximum likelihood. In this paper, we consider the robust estimation of parameters in such families of distributions. The estimation technique, which is based on optimal B-robust estimates, will assign weights to each observation and give estimates of the parameters based on the data which are well modeled by the distribution. Thus, observations which are not consistent with the proposed distribution can be identified and the validity of the model can be assessed. The method is illustrated on Venice sea level data.     

Analysis of crack movements observed in an alpine bedrock cliff

Crack widths and rock temperatures were monitored on an andestic bedrock cliff in the summit area of the Daisetsu Mountains, Hokkaido, northern Japan. Sequential data recorded the gradual widening of a crack to the point of critical crack extension, which resulted in catastrophic rock breakage. The data indicate that a combination of liquid water in?ltration into crack tip and subsequent freezing is the most signi?cant factor contributing to critical crack extension. The recorded sub‐critical crack movements involved a number of minor crack extensions and contractions, the timing of which correlates well with the magnitude of the reconstructed thermal stresses at the crack tip derived from thermal deformation of the plate‐shaped rock fragment. Larger crack extensions occurred when stress at the crack tip exceeded a threshold value, possibly re?ecting the control of rock fracture mechanics by which cracks are thought to propagate when the stress intensity factor at the crack tip exceeds the threshold values for stress corrosion cracking and the fracture toughness of the material. Copyright © 2004 John Wiley & Sons, Ltd.     

水位下降卸荷诱发库岸边坡快速失稳机理分析

本文以某工程现场岩质边坡为例，采用与传统裂隙水压力分布不同的水压力分布方式和边坡裂隙中可能发生的水锤效应相耦合，分析研究了岩质边坡发生滑动的机理及稳定性。研究表明，本文所采用的水压力分布方式较为符合边坡中的水压力分布实际情况，可以给出一个较为合理的稳定系数。当考虑水锤效应时，岩质边坡的稳定系数大大降低，说明水锤效应加剧了边坡破坏失稳的过程。本文所采用的水压力分布方式与边坡裂隙中的水锤效应相耦合的计算方法，在边坡稳定性分析中具有参考意义。     

Testing a statistical curve‐fitting procedure for quantifying sediment populations within multi‐modal particle‐size distributions

This paper describes a series of tests designed to evaluate the capacity of a personal computer (PC) based statistical curve‐fitting program called MIX to quantify composite populations within multi‐modal particle‐size distributions. Three natural soil samples were analysed by a Coulter Multisizer, and their particle‐size distributions analysed using MIX software to identify the modes, standard deviations and proportions of their composite populations. The particle‐size distributions of the three natural soil samples were then numerically combined in equal proportions using a spreadsheet program to create synthetic particle‐size distributions of known populations. MIX was then tested on the synthetic particle‐size distributions to see if the modes and proportions it identified were similar to those modes and proportions known to characterize the synthetic particle‐size distributions. The main outcome is that MIX can very accurately describe the modal particle size and proportions of the major composite populations within a particle‐size distribution. However MIX has difficulty in identifying small populations (those contributing <10 per cent of a total particle‐size distribution), particularly when they are located in the central sections of particle‐size distributions, overlain by larger populations, or when positioned in the fine tails of distributions. Despite these minor shortcomings, MIX is a valuable tool for the examination and interpretation of particle‐size data. Copyright © 2005 John Wiley & Sons, Ltd.     

Geostatistical simulation of random fields with bivariate isofactorial distributions by adding mosaic models

This work deals with the geostatistical simulation of a family of stationary random field models with bivariate isofactorial distributions. Such models are defined as the sum of independent random fields with mosaic-type bivariate distributions and infinitely divisible univariate distributions. For practical applications, dead leaf tessellations are used since they provide a wide range of models and allow conditioning the realizations to a set of data via an iterative procedure (simulated annealing). The model parameters can be determined by comparing the data variogram and madogram, and enable to control the spatial connectivity of the extreme values in the realizations. An illustration to a forest dataset is presented, for which a negative binomial model is used to characterize the distribution of coniferous trees over a wooded area.     

兰州市2001年沙尘气溶胶质量浓度的特征分析

 分析了2001年沙尘暴期间兰州与靠近沙尘源区的武威的沙尘浓度和粒径分布特征,并运用对数正态分布规律拟合了沙尘粒径的分布。通过对比武威、皋兰和兰州沙尘暴期间沙尘浓度的变化以及武威与兰州的沙尘粒径分布特征,揭示了河西走廊沙漠对兰州市沙尘暴的影响。     

Discrete element model for crack propagation in brittle materials

We propose a discrete element model for brittle rupture. The material consists of a bidimensional set of closed‐packed particles in contact. We explore the isotropic elastic behavior of this regular structure to derive a rupture criterion compatible to continuum mechanics. We introduce a classical criterion of mixed mode crack propagation based on the value of the stress intensity factors, obtained by the analysis of two adjacent contacts near a crack tip. Hence, the toughness becomes a direct parameter of the model, without any calibration procedure. We verify the consistency of the formulation as well as its convergence by comparison with theoretical solutions of tensile cracks, a pre‐cracked beam, and an inclined crack under biaxial stress. Copyright © 2015 John Wiley & Sons, Ltd.