Implications of long-term changes in valley geomorphology on the behavior of small-volume pyroclastic flows

Stratigraphic mapping in the lower 3km of the Vazcún Valley on the NE flank of Volcán Tungurahua (Ecuador) provides insight into the effects of long-term geomorphic changes on pyroclastic flow behavior. Exposures of deposits in the Vazcún Valley record activity over the last 2000years, during which time significant changes in the geomorphology of the valley have occurred. Two sets of terraces are present in the lower 2–3km of the valley, the older of which grades into a small debris fan at the mouth of the valley. Each terrace formed during a period of frequent activity that was separated by a long period of quiescence during which the Río Vazcún eroded a channel as deep as 40m reaching the previous base level. The pyroclastic flows from historical eruptions appear to have been largely contained within the channel that is cut through the higher terraces and debris fan. Their surface forms the lower terrace located upstream from the head of the debris fan. Thin pyroclastic deposits exposed within the city of Baños are mostly related to ash cloud surges that detached from the main flows as they slowed down within the channel. The lower reach of the present channel of the Rio Vazcún is very sinuous and deeply incised into the two sets of terraces. The winding channel would severely impede the mobility of future pyroclastic flows resulting in the deposition of thick deposits. Detachment of an overriding ash cloud surge could also occur in this region. Such a surge could be more likely to surmount the channel banks and travel over the surface of the terraces and debris for up to several kilometers from the channel.     

用测井资料评价煤层顶底板稳定性

根据数字测井资料计算在自然条件下岩石的弹性参数,定量预测煤层开采的工程地质条件,评价煤层顶底板岩性及其稳定性。      

Levee morphology and sedimentology along the lower Tuross River, south-eastern Australia

Levees on the lower Tuross River in south-eastern Australia reflect a complex interplay between depositional and erosional processes. Stream power, conditioned primarily by valley width, is the key determinant of levee morphology and sedimentology in this confined valley setting. Three styles of levee are described. The Rewlee levee is functionally linked to a flood channel in narrow valley settings (< 250 m). These levees contain a diverse facies assemblage characterized by various scales of erosion surfaces. Vertical accretion on levees has produced conditions under which stream power values exceed the threshold for catastrophic floodplain stripping. The levee at the Mortfield site is associated with less confined settings (valley width 500–600 m), which present lower flood stage and stream power conditions. This levee hosts a wide range of facies, but erosion surfaces are seldom observed. In the more open valley setting at the Central site (valley width 700–1000 m), levees comprise uniform, fine-grained deposits, which grade to pronounced distal floodplains with backswamps. As levees reflect a combination of within-channel and overbank processes, both depositional and erosional, these geomorphic features influence the character and sedimentology of adjacent landforms and the associated alluvial architecture of the basin.     

矿井音频电透视在任楼煤矿的应用

水文地质条件探查是任楼煤矿矿井防治水工作的首要任务。本文就作者近几年采用矿井物探技术探查水文地质条件的经验予以总结,并重点以实例介绍了应用矿井音频电透视技术探查任楼煤矿水文地质条件的效果,实践证明矿井音频透视技术是该矿探查工作面或盘区内部顶、底板内含、导水构造最有效的物探方法。      

钱塘江下切河谷SE2孔全新世沉积物黏土矿物特征及其意义*

通过X射线衍射系统分析了杭州湾地区SE2孔全新世沉积物的黏土矿物组成,结果显示研究层段黏土矿物主要由伊利石、绿泥石、高岭石和蒙脱石组成;伊利石结晶度较好,化学风化指数普遍大于0.5,表明以化学风化为主,且风化趋势自下而上呈递减趋势。通过对比中国东南部主要河流沉积物的黏土矿物组成,认为钱塘江下切河谷全新世沉积物的黏土矿物组成具有较好的物源指示意义: 全新世 Ⅰ 段(即古河口湾和河漫滩)沉积物主要来自钱塘江上游,特征黏土矿物为高岭石,河口外物质贡献不大;Ⅱ 段(即现代河口湾和近岸浅海)沉积物包含较多蒙脱石,表明不仅包括钱塘江上游物质,河口外长江物质也开始进入钱塘江河口。黏土矿物中,高岭石对气候有较好的指示作用:中全新世高岭石含量达到最高值,反映气候最为湿热,化学风化程度最高;晚全新世含量逐渐降低,反映气候逐渐回冷,化学风化强度降低。     

STUDY ON THE PHYSICAL PROCESS OF WINTER VALLEY FOG IN XISHUANGBANNA REGION*

Xishuangbanna of Yunnan Province is a famous tropical foggy region.A field experiment was carried out from November 23 to 30 of 1997 during which fogs occurred regularly every day.In the paper the characteristics of macrostructure of fog are analyzed and the physical processes of formation and dissipation of fog are studied.The results show that the Xishuangbanna valley fog forms firstly in the lower atmosphere with two-layer structures and then develops suddenly in the vertical direction after reaching the ground.Furthermore,the vegetation effect on the formation and dissipation of fog is discussed specially.     

Formation of small scale folds and faults in northern Ohio

Folds and faults in the Devonian shales of the Berea area, Ohio have been analyzed on a small scale (several meters) to determine their method of formation. A simple elastic model has been developed to account for stress concentration due to lithostatic pressures induced by local relief. This analytical model is then coupled to the beam–column buckling stability theory. The possibility of failure due to faulting is also examined using the Coulomb criterion. Initial results indicate that local stresses due to topography are a probable cause of these structures, though the possible role of regional tectonic effects cannot be eliminated. The state of the local stress field and the possibility of seismic events have important implications for surface and subsurface design problems.     

三河尖煤矿21102面底板奥灰特大突水原因及治理

2002年10月26日,三河尖煤矿21102工作面发生了底板突水灾害,分析认为突水水源为奥陶系灰岩水,导水通道为隐伏的断裂构造。为尽快恢复生产,实施了工作面两道构筑高压水闸墙的治理方案,将高压奥灰水封堵在工作面老空区内。围绕水闸墙施工出现的技术难题,采取了: a. 围岩加固防渗; b. 安装导水筒降温; c. 优化材料配比,降低水化热,提高混凝土强度; d. 自制混凝土料的搅拌、输送设备,确保大体积混凝土体的连续浇灌等技术措施。该项工程已经历了1a多的检验,堵水效果十分显著。      

Geomorphic controls on the physical and hydrologic properties of soils in a valley floor

The distribution of soil hydraulic and physical properties strongly influences runoff processes in landscapes. Although much work has been done to quantify and predict the properties of hillslope soils, far less is known about the distribution of soil properties in valley floors. A technique that links the estimation and distribution of soil hydraulic properties in valleys, with easily identified geomorphic features, was developed along a 2 km length of a valley at Brooks Creek in New South Wales, Australia. Soil physical and hydraulic property data were collected across a set of floodplain and fan features within the valley and analysed statistically to determine if soil properties varied significantly between geomorphic features and stratigraphic layers. The results show that the depth‐averaged saturated hydraulic conductivity, K_s, of the soil varies significantly with landform: fan units have K_g values that are twice that of floodplains and colluvial toeslope deposits have K_s values four times higher than floodplains. Given the notorious variability of K_s values in space, the strong statistical separation of soil properties by landform, backed up by strong separation of soil particle size by landform, suggests a way forward in understanding the distribution of soil properties in valleys and their influence on catchment hydrology. Copyright © 2000 John Wiley & Sons, Ltd.     

近断层地震下楼层竖向加速度影响因素分析

现阶段基于性能的抗震设计思想不仅关注结构自身体系的安全,而且保护非结构构件在地震作用下使用功能完好.对于工业建筑结构,生产设备在地震作用下受损会影响震后功能恢复.加速度敏感型非结构构件一般采用楼层加速度指标来量化其地震损伤程度.以三个不同高度的钢抗弯框架规则结构体系为研究对象,采用与竖向目标谱匹配的近断层非脉冲和脉冲地...