MASS MOVEMENTS AND SEDIMENT TRANSPORT AS A NATURAL HAZARD

I.INTRODUCTIONFormillionsofyearswindandwaterhaveshapedtheearth,mountainshavebeenliftedanderodedaway,waterhasevaporatedfromtheoceansandfallenbackonland,rivershaveformedandcarriedwaterandsedanmentfromthemoufltainstotheseas.Someoftherivers--suchastheColoradoRiverintheGrandCanyonregionofNorthAJnerica-foundstablecoursesastheycarvedthemselvesintotheground,others--suchastheYellowhiverinChina-havechangedtheircoursesfrequentlyallthewayintorecenthistory.Itwasonlyafewthousandyearsagothatmanstarte…     

1996年11月9日长江口外6.1级地震影响场与震中区地震地质概述

1996年11月9日长江口外6.1级地震震中位于北纬31°43’,东经123°04’震级(Ms)6.1级,震源深度7km,陆上最大地震烈度为4度。上海虽普遍有感,但无明显损失。在解译长江口外地球物理场异常的基础上,发现这次地震发生在东西向崇明—启东断裂与北东向镇海断裂的交汇部位,是北东向断裂右旋滑移的结果。     

Aquatic macrophyte distribution in Lake Manzala,Egypt

The macrophyte distribution of Lake Manzala is described in relation to water depth, salinity, dissolved oxygen, pH, Cl^–, NO ₃ ^– and PO ₄ ^3– . Changes in species composition of macrophytes are visualised by means of multivariate analysis. The TWINSPAN classification and CANOCO ordination programs (DCA & CCA) were used to analyse the data set. The classification of 100 stands revealed 8 vegetation groups which indicated eleven dominant communities. These arePhragmites australis, Typha domingensis, Scirpus maritimus, Echinochloa stagnina and Ludwigia stolonifera as emergent hydrophytes;Eichhornia crassipes andAzolla filiculoides as floating hydrophytes. The dominant submerged hydrophytes arePotamogeton pectinatus, Najas armata, Ceratophyllum demersum andRuppia maritima. The northern part of the lake with low depth and relatively high salinity has low species diversity (mainly emergent species). Species diversity increases with decreasing salinity and increasing eutrophication near the mouths of the drains in the western and southern parts of the lake. The recent changes in species distribution can be attributed to the effects of salinity, water depth and drainage water. A checklist of macrophytes in the lake is appended.     

1505年10月9日63／4级地震震中的再考证

１５０５年发生在南黄海的地震至今已有１２次震中定位。由于该震中位置的确定直接影响到一些重大工程的地震安全性评价工作，因此，本文通过收集大量影响场的历史资料，参考了国内ＩＸ度地震等震线资料，采用与地球物理场和构造条件相结合的方法，重新考证了该震震中位置。     

Effects of larval density and salinity on the development of perch larvae (Perca fluviatilis L.)

We performed two experiments, one to test whether survival and initial swim bladder inflation of perchPerca fluviatilis are affected by population density (4 or 16 larvae 1^–1) or salinity (0, 0.6 and 1.2), and the second to test the salinity tolerance of larvae. In experiment 1, survival was higher at low larval densities and at salinities of 0.6 and 1.2 rather than in fresh water. Initial swim bladder inflation was not affected by salinity or density. Average survival of fry 24 days after hatching varied from 29.6% to 86.3%, but only an average of 19.2% of the hatched larvae had grown into viable fish with an inflated swim bladder. In experiment 2, survival varied from 19% to 49%, but was not significantly affected by salinities of up to 4.8. At a salinity of 9.6, only 2 out of 344 larvae survived.     

A Breadth Averaged Numerical Model for Suspended Sediment Transport in Hooghly Estuary,East Coast of India

Sedimentation is of vital concern in the conservation, development and utilization ofour soil and water resources. The suspended sediment in estuarine waters is hazardousto navigation in estuaries, which have important ports and harbours. A breadth-averagednumerical model to study circulation and sediment transport is presented in this paper.The model is applied to Hooghly estuary, along the east coast of India. The model is fullynon-linear and uses a semi-explicit finite difference scheme to solve mass, momentum andadvection diffusion equation for suspended sediments in a vertical plane. The erosion anddeposition have been computed by empirically developed source and sink terms in thesuspended sediment equation.     

土的力学性质对冻胀力影响的试验研究

Frost heaving stresses are a result of thermal, mechanical, and chemical forces. The process is complicated, and despite numerous publications on the subject, as yet there is no clear consensus on the model of mechanical interaction for soil freezing. Frost heaving stresses depends on mechanical properties of soil and conditions of measurements. Mechanical equilibrium between water, ice and soil particles based on the generalized Clapeyron equation and deformability of the components is considered. Increase of volume of freezing soil due to water flow to freezing fridge and phase transfer affects surrounding soil layers and appears to be the major reason of change of stress-strain conditions. A simplified model of mechanical interaction between soil and engineering construction is proposed. Experimental results of study of frost heaving forces by sensors of variable frigidity are presented. The experiments with different types of soil in conditions of open and close system were performed to provide a basis for the model and further estimations. Ongoing improvements and possible applications are discussed.     

四川省南江县水洞乡安家坪、混家坪地下采煤地质环境影响评价

四川省南江县水洞乡蕴藏着丰富的煤炭资源，且煤质好，市场上较为畅销，目前，该区以采煤为主的矿业经济较为发达，有国营及私营煤矿企业约十多家，其采煤方式均为地下坑采。由于该区采煤历史已有数十年，特别是20世纪80年代以来，矿山生产规模日益增大，地下形成大面积的采空区，近年来，于煤矿开采范围出现了较多的房屋变形开裂等迹象，且区内滑坡、崩塌等地质灾害也有增多的趋势，由此而引发当地群众与矿山企业之间的纠纷也有所增多。为此，需查明地表建筑变形及滑坡、崩塌等地质灾害与地下采煤活动的关系，一方面便于科学、公正、合理地解决纠纷，另一方面也便于指导矿山企业的开采，避免采矿诱发更多的地质灾害，为此需对地下采煤活动进行地质环境影响评价。文章论述运用采空区顶板变形分带法和深厚比指标判别法，对水洞乡安家坪、混家坪一带地下采煤对地质环境的影响进行综合评价的情况。     

小浪底水库蓄水运行对矿井水害防治的影响评价

新安煤矿系我国大水矿区,地下水害严重威胁着矿井的安全生产。本文根据大量原始资料,运用灰色系统理论和风险分析理论,讨论了小浪底水库蓄水运行对新安煤矿水害防治所造成的影响,明确指出水库蓄水后矿井突水威胁主要来自断层水及石炭系太原群L7～8岩溶水;煤矿防治水的重点应该是治理L7～8灰岩及矿区边界断层在库区的露头或隐伏露头。     

永安井水位大幅度异常成因的调查分析

2001年7月18日起,永安井水位出现了持续的大幅度上升的变化过程。经调查落实,这是由于该井附近的另一口并多年来的开采后,于2001年7月18日突然停止抽水,而使地下水的补给量增大,造成地下水大幅度上升。这对研究临近并抽水对地震地下水动态观测井的水位动态影响提供了实例,对区分深井地下水前兆异常与抽水干扰有一定的参考价值。