古尔班通古特沙漠季节性冻土入渗特性试验研究

以古尔班通古特沙漠南缘融雪期冻结土壤入渗试验为依据,分析了沙漠地区季节性冻土水分入渗特性及主要影响因素.结果表明:沙漠地区季节性冻土具有较高的入渗能力,沙漠冻结风沙土的稳渗率为0.26～0.30 mm/min,是田间冻结壤土的10～20倍,可以保证融雪水及时入渗进入土壤,为融雪水的高效储存创造了有利条件.入渗能力随着土壤含水率的升高而减小.沙地土壤初始的低含水率、土壤大孔隙结构特征是沙地冻结土壤具有较高入渗能力的主要原因.研究结果为进一步研究春季融雪水在沙地的再分配过程奠定了基础.     

乌鲁木齐碗窑沟断层电阻率成像探测与探槽剖面的对比研究

利用电阻率二维层析成像方法对碗窑沟断层进行了试验探测,获得了该断层典型的电阻率成像异常特征:地层电性结构存在强间断面,呈现明显的"二分"现象,高、低阻间的梯度界线倾向低阻区。在对乌鲁木齐地区其它具有类似构造特征的断层进行探测时,电阻率成像剖面呈现出相似的异常特征,说明这一异常特征可以作为乌鲁木齐地区判定断层的重要标志和依据。乌鲁木齐地区多为高角度的逆冲断层,此类构造电阻率成像剖面中高、低阻之间的界线与断层并不重合,断层处于高阻区域,倾向与视电阻率衰减梯度线倾向相反,断层的真实位置与图像最上部高、低电阻转折的拐点部位最接近     

Field study of macropore flow processes using tension infiltration of a dye tracer in partially saturated soils

Macropores are important preferential pathways for the migration of water and contaminants through the vadose zone. The objective of this study was to examine small‐scale preferential flow processes during infiltration in macroporous, low permeability soils. A series of tension infiltration tests were conducted using Brilliant Blue dye tracer at two field sites in southwestern Ontario, Canada. The maximum applied pressure head was varied for each test and the resulting dye stain patterns and macropore networks were characterized by excavation, mapping, photography, and image analysis. Worm burrows were the dominant macropore type, with average macropore densities exceeding 400 m^?2 and peak densities of more than 750 m^?2 at 30 cm depth at both sites. Flow in macropores became significant at infiltration pressures > ? 3 cm, with corresponding increases in infiltration rate, soil water content variability (spatially and temporally), and depth of dye staining. The results demonstrated clear evidence for partially saturated macropore flow under porewater tension conditions and the associated importance of macropore–matrix interaction in controlling this flow. Field observations of transient infiltration showed that film and rivulet flow along macropores yielded vertical flow velocities exceeding 40 m d^?1. Simple calculations showed that film flow along the walls and corners of irregularly shaped macropores could explain the observed results. Copyright © 2009 John Wiley & Sons, Ltd.     

Coupling the Xinanjiang model to a kinematic flow model based on digital drainage networks for flood forecasting

The Xinanjiang model, which is a conceptual rainfall‐runoff model and has been successfully and widely applied in humid and semi‐humid regions in China, is coupled by the physically based kinematic wave method based on a digital drainage network. The kinematic wave Xinanjiang model (KWXAJ) uses topography and land use data to simulate runoff and overland flow routing. For the modelling, the catchment is subdivided into numerous hillslopes and consists of a raster grid of flow vectors that define the water flow directions. The Xinanjiang model simulates the runoff yield in each grid cell, and the kinematic wave approach is then applied to a ranked raster network. The grid‐based rainfall‐runoff model was applied to simulate basin‐scale water discharge from an 805‐km² catchment of the Huaihe River, China. Rainfall and discharge records were available for the years 1984, 1985, 1987, 1998 and 1999. Eight flood events were used to calibrate the model's parameters and three other flood events were used to validate the grid‐based rainfall‐runoff model. A Manning's roughness via a linear flood depth relationship was suggested in this paper for improving flood forecasting. The calibration and validation results show that this model works well. A sensitivity analysis was further performed to evaluate the variation of topography (hillslopes) and land use parameters on catchment discharge. Copyright © 2009 John Wiley & Sons, Ltd.     

土石混合体边坡人工降雨模拟试验研究

降雨入渗是诱发土石混合体边坡失稳的主要因素之一,此类问题一直受到人们的关注,但对此问题的研究不够系统和深入。为了对降雨入渗诱发下土石混合体滑坡的失稳机理有较深的了解及研究边坡性状随时间变化的一些重要特性,在上瑞高速公路贵州段选取了一个典型的土石混合体边坡进行人工降雨模拟试验和原位综合监测。监测成果表明：降雨入渗影响下土石混合体边坡的滑动变形区为坡面以下0～4 m之间,变形量以坡面最大,从坡面到坡体深部逐渐减小;在实施降雨的前2 h,平均入渗百分率为86 %,之后,入渗率由于地表径流的增加而随时间逐渐减少,一段时间(6 h)之后,入渗率降到一个相对稳定值(50 %);降雨入渗造成土体中孔隙水压力增加,致使边坡土体的抗剪强度由于有效应力的减少及土体吸水软化而降低,降雨入渗的这一双重效应可能是降雨诱发土石混合体边坡失稳的主要原因之一。     

印度尼西亚两次特大地震引发海啸和不引发海啸的比较研究

2004年12月26日苏门答腊岛安达曼海附近海域发生的9．0级地震和2005年3月28日苏门答腊岛明打威群岛北附近海域的8．7级地震,在构造环境、震级、震源深度、地震类型都相似的情况下,为何前者引发海啸,后者不引发的海啸？对此进行了对比分析,认为9．0级地震发生时,在其震源体附近的两板块相交的海沟两侧陡坡蕴育着滑坡体或和崩塌体（或者两者都有）,9．0级地震发生时,强烈的地震波,促使滑坡体的滑动或崩塌体的崩塌,推压和扰动海水,引发诲啸。而8．7级地震发生时、在其震源体附近的两板块相交的海沟两侧陡坡无滑坡体或和崩塌体,或先存滑坡体或崩塌体在9．0级地震发生时已滑坡或崩塌殆尽,当8.7地震发生时,无滑坡体滑动或崩塌体崩塌,不可能对海水有较大的扰动,故不可能引发海啸。     

降雨渗流及干湿循环作用下红砂岩顺层边坡稳定性分析

针对红砂岩顺层岩质边坡稳定性问题,建立顺层岩质边坡力学模型,对降雨渗流条件下边坡受到的力学作用进行了计算;选取典型结构面,通过室内干湿循环试验,分析了结构面强度参数衰减规律;综合考虑降雨渗流及结构面强度弱化,对降雨渗流及干湿循环综合影响下红砂岩顺层岩质边坡稳定性进行了分析,获得了边坡稳定性衰减变化规律;通过炎汝高速公路边坡稳定性监测对理论计算结果进行了验证。结果表明,边坡受到的水力作用与后缘张拉裂隙充水高度呈正比;干湿循环作用下,结构面黏聚力呈幂指数形式衰减,内摩擦角呈二次函数衰减;边坡稳定性与后缘张拉裂隙充水高度呈线性关系,而与干湿循环呈指数关系,且干湿循环对边坡稳定性影响比后缘裂隙充水高度大;在降雨渗流及干湿循环综合作用下,边坡稳定性系数降低了约66%,较考虑单一影响因素有了大幅度降低;边坡稳定性监测结果与理论计算结果吻合较好,进一步证明了理论计算结果的正确性。     

Modified models for better prediction of infiltration rates in trapezoidal permeable stormwater channels

ABSTRACT

In stormwater management, it is important to accurately quantify the infiltration rates to solve urban runoff-related problems. This study proposes a method to improve estimates of the infiltration rate in permeable stormwater channels. As part of the analysis, five infiltration models were evaluated: the Kostiakov, Horton, modified Kostiakov, Philip and SCS (Soil Conservation Service) models. Infiltration tests with various initial water levels were performed on channel models with differing base width and side slopes. The results show that the addition of three parameters that describe the trapezoidal cross-sectional area, i.e. the depth, side slope and base width, in the infiltration models yielded better estimates of the infiltration rate. A comparison of the infiltration capacity values obtained from the models after the three parameters were added with those that were experimentally obtained, shows that the improved modified Kostiakov model is the most suitable model to predict infiltration rates in trapezoidal permeable stormwater channels.     

Effects of hillslope geometry on spatial infiltration using the TOPMODEL and SCS-CN models

ABSTRACT

The estimation of infiltration is a main issue in runoff simulation. The geometry of hillslopes (plan shape and profile curvature) may affect the responses, as well as infiltration over the hillslopes. In this study, the equations of TOPMODEL (a topography-based model) were applied to complex hillslopes to develop the complex TOPMODEL. This model was coupled with the SCS-CN (Soil Conservation Service Curve Number) model to examine the effects of geometry on infiltration and derive a saturation excess-based curve number (CN). The effects of plan shape and profile curvature upon the spatial distribution of CN and infiltration were studied. The results show that convergent hillslopes have 15.4% less infiltration and divergent hillslopes have 7.8% more infiltration than parallel ones. The infiltration over concave hillslopes is 13.5% lower and infiltration over convex hillslopes 5.8% higher than for straight ones. The degree of convergence/divergence has a greater effect on the CN compared to that of profile curvature.     

口泉断裂口泉村段断裂特征研究

口泉断裂是大同盆地西缘的主控边界断裂,本文采用野外地质调查、布设地震钻孔、浅层人工地震勘探、电阻率CT法勘探和探槽开挖的手段,对该断裂在口泉村段的断裂特征进行了分析。