Cavity expansion analyses of crushable granular materials with state‐dependent dilatancy

Crushability is one of the important behaviors of granular materials particularly under high stress states, and affects both the deformability and strength of the materials that are in essence associated with state‐dependent dilatancy. In this presentation, first, a new critical state model is proposed to take into account the three different modes of compressive deformation of crushable granular materials, i.e. particle rearrangement, particle crushing and pseudo‐elastic deformation. Second, the governing equations for cavity expansion in crushable granulates are introduced, in which the state‐dependent dilatancy as well as the bounding surface plasticity model are used. Then, the procedure to obtain semi‐analytical solutions to cavity expansion in the material is described in detail, in which a commercial differential equation solver is employed. Finally, cavity expansion analyses are carried out on Toyoura sand, a well‐documented granular material, to demonstrate the effects of crushability and state‐dependent dilatancy. The study shows that particle crushing does occur at both high stress and critical states and affects the stress fields and the deformation behavior of the material surrounding the cavity in association with state‐dependent dilatancy. This leads to conclusion that particle crushing and state‐dependent dilatancy have to be taken into account when cavity expansion theory is used to interpret cone penetration tests and pressuremeter tests. Copyright © 2011 John Wiley & Sons, Ltd.     

变差函数参数的计算

为了求出地质统计学中变差函数理论模型的参数，首先把相应模型化成线性函数的形式，多面手应用线性方程组非负解的理论计算出它的参数。     

地下爆炸成腔注浆支护的小型实验研究

针对爆扩成腔稳定性差、渗水率高及遇水坍塌等问题，采用注浆抽浆法对爆炸空腔进行了支护，并进行防渗小型实验研究。确定了注浆临界水灰比为0.8:1，分别对重力注浆、压力注浆以及压力注浆加防水剂和无支护的4个空腔进行了支护对比实验。实验表明：重力注浆不足以达到要求，压力注浆是一种解决支护和防渗较为可行的方法，加入防水剂后效果更好。     

Pile driving by numerical cavity expansion

A cavity expansion procedure for the simulation of pile driving is presented and assessed in this paper. The analysis uses a non-linear finite-element model and the penetration of the pile into the soil is simulated by a radial opening of the soil around the pile. The case of a pile advanced by expansion will be compared to a similar pile subjected to computational driving (referred to, respectively, as ‘expanded’ and ‘driven’ piles for convenience). The state of stress and deformation, and the evolution of pore-water pressure in the soil will be monitored for the expanded and driven piles. Further computational driving will be applied to both cases and the pile response and soil resistance will be compared. The computational cost of advancing the pile by expansion will finally be investigated. Copyright © John Wiley & Sons, Ltd.     

页岩孔隙度测量实验方法分析与评价

页岩气是目前国内外非常规油气领域研究的热点,有效的页岩孔隙度值是评价页岩储层物性的重要参数。由于页岩本身具有易碎的特点,导致钻取柱体样品难度大,很多学者采用碎样法计算孔隙度,但碎样法与柱体法的差别及测定结果的有效性并未见相关研究成果。本文对相同样品通过三种不同方法:氦气膨胀法测孔隙度(柱体),真、视密度法及低温氮气吸附实验法(样品粉碎至40~60目)分别计算孔隙度。结果发现三种方法测定的三组孔隙度数值不同,每种方法在样品制备上及实验方法的差别是影响实验结果的主要因素,为检验三组孔隙度值的有效性,采用数理统计中的单因素方差分析法进行分析,结果表明页岩柱体与粉碎至40~60目范围内的页岩样品测量的孔隙度值虽有差别,但在有效范围内,具有一致性。但是将页岩粉碎后,页岩中的有效孔隙变化程度较大,故用柱体测定的有效孔隙度法优于其他两种碎样方法。     

用弹性圆薄板理论分析盐岩单井水溶溶腔覆岩关键层

本文系统分析了岩盐单井水溶开采的特征, 应用弹性圆薄板理论对溶腔覆岩关键层进行分析, 推导出了溶腔覆岩层下沉变形微分方程和溶腔覆岩关键层上的载荷计算式, 并对溶腔覆岩关键层受力特征进行了分析, 推导了溶腔覆岩关键层初次破断距计算式, 建立了适用于岩盐单井水溶开采溶腔覆岩关键层判别的判据式, 是对以往关键层理论研究成果的补充, 为关键层理论应用于岩盐单井水溶开采溶腔覆岩移动规律研究打下了理论基础。最后, 对岩盐单井水溶开采覆岩控制研究内容和关键层理论在其中的应用思路进行了初步探讨。     

Study of the crust and mantle using magnetic surveys by Magsat and other satellites

Among the first measurements made from near-Earth orbiting satellites were measurements of the magnetic field. The sources of that field lie both within the Earth, in its core and crust, and in the surrounding ionosphere and magnetosphere. This article summarizes some of the methodology and results for studies of the Earth’s mantle and crust. Mantle conductivity studies can be made either by studying signals impressed on the Earth from outside, e.g., the ionosphere or magnetosphere, or by studying signals originating in the core and transmitted through the mantle. Crustal field studies begin with a careful selection of the data and subsequent removal of core and external fields by some sort of filtering. Average maps from different local times sometimes differ, presumably due to the remaining presence of fields of external origin. Several techniques for further filtering are discussed. Where large-area aeromagnetic maps are available, crustal maps derived from satellite data can be compared with upward continued data. In general, the comparisons show agreement, with some differences, particularly in and near the auroral belts. The satellite data are further reduced by various methods of inverse and forward modelling, sometimes including reduction to the pole (RTP). These techniques are generally unstable at the equator. Common methods of stabilizing the inversions include principle components analysis and ridge regression. Because of the presence of the core field, the entire crustal contribution from the field is not known. Also, there is a basic nonuniqueness to the inverse solutions. Nevertheless, magnetizations that are interpretable can be derived.     

Efficiency of kriging estimation for square, triangular, and hexagonal grids

Although several researchers have pointed out some advantages and disadvantages of various soil sampling designs in the presence of spatial autocorrelation, a more detailed study is presented herein which examines the geometrical relationship of three sampling designs, namely the square, the equilateral triangle, and the regular hexagon. Both advantages and disadvantages exist in the use of these designs with respect to estimation of the semivariogram and their effect on the mean square error or variance of error. This research could be used to design optimal sampling strategies; it is based on the theory of regionalized variables, in which the intrinsic hypothesis is satisfied. Among alternative designs, an equilateral triangle design gives the most reliable estimate of the semivariogram. It also gives the minimum maximum mean square error of point estimation of the concentration over the other two designs for the same number of measurements when the nugget effect is small relative to the variance. If the nugget effect is large (.90 ² or more), and the linear sampling density is >0.85r where r is the range, the hexagonal design is best. This study computes and compares the maximum mean square error for each of these designs.     

Holocene initiation and expansion of the southern margins of northern peatlands triggered by the East Asian summer monsoon recession

Northern peatlands represent one of the largest biospheric carbon reservoirs in the world. Their southern margins act as new carbon reservoirs, which can greatly influence the global carbon dynamics. However, the Holocene initiation, expansion and climate sensitivity of these peatlands remain intensely debated. Here we used a compilation of basal peat ages across six isolated peatlands at the southern margins of northern peatlands to address these issues. We found that the earliest initiation event of these peatlands occurred after the Younger Dryas (YD, 12,800–11,700 years ago) period. The second initiation event and rapid expansion occurred since 5 ka cal. BP. The recession of East Asian summer monsoon (EASM) during the YD period and at around 5 ka cal. BP likely played a major role in controlling the initiation and expansion of these peatlands. The rapid expansion of these peatlands possibly contributed to the significant increases in atmospheric methane concentrations during the late Holocene because of the minerotrophic fens status and rapid expansion of them. These ecological processes are different from northern peatlands, indicating the special carbon sink and source implications of these peatlands in the global carbon cycle.     

福建云霄晶洞花岗岩及含石榴子石伟晶岩的硅氧同位素研究

在运用常规方法和激光烧蚀同位素分析方法分别对云霄晶洞花岗岩和伟晶岩(长石、石英和石榴子石)的硅、氧同位素组成进行研究的基础上,探讨了晶涧花岗岩及其含石榴子石伟晶岩的物质来源及形成条件.伟晶岩中的石英和长石的氧、硅同位素组成分别较之花岗岩中的石英和长石的氧、硅同位素组成,均未发生明显变化,表明二者岩浆来源一致.云霄县的乌...