堆石料单粒强度尺寸效应的颗粒流模拟方法研究

围绕堆石料单粒强度尺寸效应的颗粒流模拟方法展开研究。首先,基于FISH二次开发建立了堆石料的随机不规则单粒模型,充分考虑堆石料的形状特征和破碎现象;然后,建立了堆石料单粒强度尺寸效应的等效模拟方法,以单粒强度随其粒径的变化规律为基础,推导了堆石料模型中细观黏结强度与堆石料等效粒径的负指数经验公式;其次,基于建立的数值模型对堆石料的室内单粒压缩试验进行仿真模拟,验证数值模型的正确性和合理性,并对较大粒径堆石料的单粒强度进行模拟预测,突出数值试验的优势;最后,基于建立的数值模型对相同粒径不同形状特征堆石料的单粒强度分布特征进行模拟研究。研究结果表明：（1）堆石料内部缺陷含量和尺寸随粒径增加对其单粒强度所产生的尺寸效应,可通过堆石料模型中细观强度参数随粒径折减进行等效模拟;（2）形状特征对堆石料的破裂机制具有重要影响,方形颗粒为压剪破裂,单粒强度较高,而随机不规则颗粒和圆形颗粒为拉剪或劈裂,单粒强度相对较低;（3）拉剪或劈裂条件下,堆石料形状越不规则,其单粒强度的离散程度越高,反之则离散程度越低。相关研究成果可为进一步研究荷载作用下堆石体内各粒径段堆石料的破碎量奠定基础,从而更加真实地反映堆石体的级配演化规律。     

库姆塔格沙漠东南缘BL剖面粒度记录的全新世快速气候事件

地质历史过程中全新世时期是一个温暖湿润的间冰期气候过程,中间出现过多次变冷或变干的快速气候事件。BL剖面位于库姆塔格沙漠东南缘,是一典型的风成砂黄土沉积地层,沉积厚度约350 cm。通过沉积地层光释光测年和沉积物粒度变化分析,结果显示：（1）BL剖面沉积的年代始于8.3 ka,处在全新世早期;（2）区域干旱气候条件下,反映冬季风的代用指标则以粗端组分含量为主,BL剖面沉积物平均粒度受到颗粒粗端的影响较大,对比3个不同粗颗粒组分含量所指示的古气候变化,选用>110 μm的沉积物颗粒组分含量作为冬季风研究的替代性指标,具有较好的指示意义;（3）剖面粒度对全新世中晚期的6次气候快速变化过程均有不同程度的记录,其特点是对全球性冷事件敏感性较强,对干旱事件响应较弱。对库姆塔格沙漠地区全新世气候过程的研究,可为极端干旱区域气候对全球气候变化过程的响应提供一定借鉴。     

Influence of shear speed and normal stress on the shear behavior and shear zone structure of granular materials in naturally drained ring shear tests

“Sliding Surface Liquefaction” is a process causing strength loss and consequent rapid motion and long runout of certain landslides. Using a new ring shear apparatus with a transparent shear-box and digital video camera system, shear-speed-controlled tests were conducted on mixed grains (mixture of three different sizes of sand and gravel) and mixed beads to study shear behavior and shear zone development process under the naturally drained condition in which pore pressure is allowed to dissipate through the opened upper drainage valve during shearing. Higher excess pore water pressure and lower minimum apparent friction were observed in the tests where grain crushing was more extensive under higher normal stress and higher shear speed. Along with the diffusion of silty water generated by grain crushing, smaller particles were transported upward and downward from the shear zone. Concentration of larger grains to the central and upper part of the shear zone was confirmed by means of visual observation together with grain size analysis of sliced samples from several layers after the test. On the other hand, smaller particles were accumulated mostly below the layer where larger grains were accumulated. The reason why larger grains were accumulated into the shear zone may be interpreted as follows: grains under shearing are also subjected to vertical movement, the penetration resistance of larger grains into a layer of moving particles is smaller than that into the static layer. Therefore, larger grains tend to move into the layer of moving grains. At the same time, smaller particles can drop into the pores of underlying larger grains downward due to gravity.     

洛川黄土细颗粒混合矿物红外释光信号 异常衰减的初步研究*

对洛川末次冰期的黄土细颗粒混合矿物红外释光(IRSL)信号异常衰减行为的初步研究结果表明: 1)预加热只能部分消除异常衰减对等效剂量测定的影响,不能完全消除这种影响,IRSL异常衰减过程也许存在着热效应和非热效应两种组分; 2)对16个已知年龄的马兰黄土(15~70ka)样品细颗粒混合矿物天然IRSL信号的ED值与期望ED值的比较初步显示,马兰黄土细颗粒混合矿物IRSL信号异常衰减不断发生,导致混合矿物IRSL的年龄测定值可能被低估达20 ％ 以上。     

塔里木盆地志留系沥青砂岩有效厚度的确定方法

塔里木盆地志留系具有分布广泛的沥青砂岩,沥青砂岩段厚度在各个地区具有不均匀性,从几米到一百多米不等。岩心观察发现沥青砂岩段内并不全含有沥青,岩心剖面上呈现“黑白砂相间”的现象,“黑砂”的部分为含沥青层段,“白砂”的部分为不含沥青层段。弄清“白砂”中曾经是否有油气进入,对志留系沥青砂岩中沥青含量、古油藏油气储量的计算及志留系剩余油气资源量的评价具有重要的意义。本文通过对志留系沥青砂岩段的“黑砂”与“白砂”分别取样,采用物性测定、显微镜下岩性观察、含油包裹体颗粒指数(GOI)数据观测及定量颗粒荧光(QGF)指数测定等多种方法和技术手段对沥青砂岩段的“黑砂”与“白砂”进行对比研究。结果表明,沥青砂岩段的“白砂”没有油气进入或进入的油气量很少,在确定志留系沥青砂岩有效厚度时应剔除“白砂”层的厚度。     

Carbon altotropic composition of interstellar grains

Extinktionskurven für Kern-Mantel-Teilchen und für Vielkernteilchen, die allotrope Kohlenstoffmodifikationen enthalten, werden mit Extinktionsbeobachtungen der Sterne R CrB und R Y Sgr im fernen UV sowie mit der interstellaren Extinktion verglichen. Wir zeigen, daß dieses Teilchenmodell mit der beobachteten Extinktion im fernen UV verträglich ist, finden jedoch, daß nur Teilchen, in denen amorpher Kohlenstoff von Graphit ist, die interstellare Extinktionskurve und die der R-CrB-Sterne gut wiedergeben.