节理岩体卸荷强度特性的试验研究

卸荷状态工程岩体的强度特性与传统的加载岩体有本质的区别。目前对于岩石卸荷强度特性的研究比较多见,但对于含节理的岩体在卸荷应力状态下的强度特性,尤其是节理面对其强度的影响研究实属少见。本文通过岩体三轴模拟试验研究了卸荷应力状态下节理岩体的破坏特征,突出考虑了节理面性质对卸荷强度的影响,在此基础上提出了节理岩体卸荷强度准则的一般表达式并进行了对比验证。     

肋柱式锚杆支挡结构的徐变次内力分析

采用老化徐变理论和等效弹性模量法,对肋柱式锚杆支挡结构的徐变影响提出了具体计算方法,并通过实例计算了支挡结构的徐变次内力。计算结果表明,在逆作法条件下,随着开挖深度的加大,岩土侧向压力也增大,使后期施工的混凝土构件产生的徐变次内力也随之增大;考虑徐变后使结构设计更加安全可靠,尤其坡脚处后期浇筑的混凝土构件,更要关注徐变的影响。     

动态最小二乘支持向量机学习算法

针对大样本集的训练问题和动态训练样本的模型更新问题,提出了动态最小二乘支持向量机学习算法.该算法充分利用已建好的模型,逐渐加入新样本,并可删除位于任何位置的非支持向量,避免了矩阵求逆运算,保证了算法的高效率.大坝变形及电离层延迟两个时间序列的预报实例表明,该算法具有计算时间短、预报精度高的特点.     

应用生烃动力学法研究川东上二叠统烃源岩生烃史

现今川东上二叠统烃源岩生烃史研究具有局限性.首先,没有对上二叠统Ⅰ-Ⅱ1型灰岩生油、Ⅲ型泥岩的生气史分开评价;其次,海相镜质组反射率通过拟合公式换算成镜质体反射率评价烃源岩成熟度具有局限性.针对上述不足,笔者通过热模拟实验,利用化学动力学方法,标定出两类源岩生油、生气的动力学参数,并结合川东地区的埋藏史及热史,模拟出源岩有机质的成烃转化率曲线.研究表明:上二叠统灰岩、泥岩有机质在距今200 Ma和190 Ma分别进入了生油、生气门限,而在距今170 Ma和140 Ma生烃结束.     

Rock magnetic record of Cenozoic lake sediments from the Linxia basin and aridification of the Asian inland

High resolution research of rock magnetic records and quartz sands from the Maogou Section in the Linxia basin reveals that after a relatively stable environment between 13.07 Ma and 8.6 Ma, the basin was gradually influxed by eolian dusts at about 8.6 Ma, with two rapid increases at about 6.4 Ma and 5.3 Ma, respectively. The study suggests that drying of northwest China began at 8.6 Ma and strengthened rapidly at about 6.4 Ma and 5.3 Ma. __________ Translated from Marine geology & Quaternary geology, 2007, 27(4): 103–110 [译自: 海洋地质与第四纪地质]     

The paleoclimatic records and the relevance with the formation of hydrocarbon source rocks:A case study of Huanghekou depression,Bohaiwan basin

Bohaiwan basin, covering an area of 200 000 km², is one of the most important oil-bearing basins in Eastern China. Rifting processes formed the basin, and two evolution phases can be recognized. The rifting phase developed in Paleogene, and post-rifting phase occurred in Neogene. More than 200 oil fields have been found in the onshore and offshore area in Bohaiwan basin in recent years. The distribution of the oil fields is closely related to the rich hydrocarbon depressions, and the Huanghekou depression is one of these rich hydrocarbon depressions. A number of large and medium-sized oil and gas fields have been found in this area, such as BZ25-1, BZ34 etc., and the hydrocarbon was mainly from the Huanghekou depression. The formation of rich hydrocarbon source rocks depended on the tectonic setting of rapid subsidence, favorable paleoclimatic conditions and paleolimnology environments. The effects of paleoclimatic condition on hydrocarbon source rocks are the focus of this paper. __________ Translated from Geological Bulletin of China, 2007, 26(7): 830–840 [译自: 地质通报]     

四川盆地泸州古隆起嘉陵江组储层特征研究

对研究区嘉陵江组沉积背景认识的基础上,通过岩心观察、岩石薄片确定了不同类型的储集岩和储集空间,得出本地区储层岩石类型和储渗空间类型均多样化的特点。从成因角度识别出来了溶蚀孔隙型储层、膏溶孔洞型储层、裂缝型储层等三类储层。研究不同类型储层的孔、渗特征及关系表明,溶蚀孔隙型储层物性要优于膏溶孔洞型储层,而溶蚀孔隙型储层中的颗粒云岩溶蚀孔隙型储层物性最好、颗粒灰岩溶蚀孔隙型物性其次、粉晶云岩溶蚀孔隙型储层物性最差,其原因是不同储层受沉积环境和成岩作用控制和影响。     

Micromechanics of the velocity and normal stress dependence of rock friction

Among the second-order effects on friction the most important are those of variable normal stress and of slip velocity. Velocity weakening, which is usually considered the source of the stick-slip instability in rock friction, has been observed in velocity stepping experiments with Westerly granite. The friction change, , was –0.01 to –0.008 for a tenfold velocity increase. Using normal closure measurements, we observed dilation upon each increase in sliding rate. We also observed, for the first time, time-dependent closure between surfaces during static loading. The dilation that occurred during the velocity stepping experiment was found to be that expected from the static time-dependent closure phenomenon. This change in closure was used to predict friction change with an elastic contact model. The calculated friction change which results from a change in contact area and asperity interlocking, is in good agreement with the observed velocity dependence of steady-state friction. Variable normal stress during sliding has two effects, first in creating new partial slip contacts and locking some existing fully sliding contacts and second in increasing interlocking, for instance when normal load is suddenly increased. As a result, a transient change in friction occurs upon a sudden change in normal load.     

Textural segmentation of digital rock images into bedding units using texture energy and cluster labels

The texture of digital rock images, as recorded, for instance, with borehole imaging devices, is shown to reflect different bedding types. Textural segmentation of borehole images, therefore, subdivides the recorded sequence into bedding units. We show that a textural segmentation algorithm based on the concept of texture energy achieves good results when compared with synthetic as well as real data in which petroleum geologists have performed zonations on cores. Texture energy involves filtering of the original image with a set of texture sensitive masks. The filtering is done as a finite convolution over the size of the masks. On the resulting images the variance is computed over a relatively large sliding window, which, in its practical implementation, covers the full width of the image. The resulting nine one-dimensional curves are then clustered hierarchically into a user-determined number of image texture or lithological bedding classes. Principal component analysis previous to clustering can be used to reduce redundancy in the data. A recurring and relatively ill-defined problem in this field are macro-textures, i.e., the cyclic interbedding of two or more bedding types. We show that sliding Fourier transforms and variable mask scale can successfully address the zonation of macro-textures. In general, the method gives best results with mask sizes equivalent to 2–4 centimeters, reflecting the length scale at which the investigated geological bedding seems to have its highest variation.     

Extension of the solution of Kepler's equation to high eccentricities

The classic Lagrange's expansion of the solutionE(e, M) of Kepler's equation in powers of eccentricity is extended to highly eccentric orbits, 0.6627 ... <e<1. The solutionE(e, M) is developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients of the expansion are given in terms of the derivatives of the Bessel functionsJ _n (ne). The expansion is convergent for values of the eccentricity such that |e–e*|<(e*), where the radius of convergence (e*) is a positive real number, which is calculated numerically.