Discrete Element Analysis of Huangtupo Landslide

Journal of Chima University of Geosciences, Vol. 13，No. 1, p. 83 - 85, March 2002ISSN 1002 - 0705Printed in ChinaDiscrete Element Analysis of Huangtupo Landslide *An Guanfeng Yin Kunlong Tang Huimingp5AEngineering Faculty , China University of Geosciences , Wuhan 430074ABSTRACT: On the basis of the deep geology and the geological structure of Huangtupo landslide, anancient landslide ia the reservoir of the Three Gorges, the geo-environmental model of the landslide is es-tablished to analyze quntitatively the slidig mechanism by using the discrete element method. It is con-cluded that interbedding structure of soft and hard formation consists of the main geological background,which induced the arching of the formation under gravity. Stability anlysis of different loadings showsthat the ground building weight on the middle slope may restrain the extension of shear sliding zone be-low. but may activate the foot area which will reduce the safety factor of the front.KEY WORDS: Huangtupo landslide, geological model, discrete element method, landslide mechanism,LANDSLIDE INTRODUCTIONThe exposed rock at the head of HuangtupoHuangtupo landslide, located on the southern landslide is Lower Triassic limestone seriesbank of the Yangtz River about 1 km upstream to the Jialingjiang Formation whose dip angle is steep. TheBadong County in Hubei Province, is an ancient field geological investigation and the deep geophysicallarge-scale landslide with an area of 1.38 km2, an av- exploration have proved that a fault lies betweenerage thickness of 30 m, and a volume of 4X 10' m'. Jialingjiang Formation limestone and Badong Forma-Since 1982, large-scale civil engineering construction tion mudstone.has been conducted on the landslide, due to improperThe stratum envolved in the Huangtupo land-geological conclusion. Up to now, the town has come slide are limited to the superlicial layer of the syn-into being. After 1992, new engineering geological cline, which belongs to the ancient landslide bodyinvestigation prompts new town to be shifted to the formed during the downcutting of the Yanglze River.Xirangpo 5 km upstream from the landslide ( Wu,According to the deep geology and the geological1999 ; Zhonget al,，1992).structure of the superficial ancient landslide body,The foot elevation of Huangtupo landslide is 80 the geo environmental model of the Huanglupo land-ma. s. 1. on the river, while the head elevation is slide is established. Discrete element numerical simu-640 ma. s. 1.. The slope varies from 30° to 40° un-lation method is used to study the relationship beder the elevation of 225 m, and the middle section of tween the Huangtupo landslide and its deep geolog-the slope is about 20°. The landslide consists of Mid- ical stratum, and to predict and evaluate the stabilitydle Triassic series Badong Formation, amaranth mud- of the landslide in difeent loeds.stone including siltstone, marlite and a broken blockstructure. The landslide area is located on the south-PRINCIPLE OF DISCRETE ELEMENT METHODern part of Guandu syncline whose axis extends alongThe discrete element method can be used to solvethe river bed. The sedimentary bedding dips towards efietively the interaction among the blocks andthe river, and the bedding is wave shaped, belonging movement procedure under the block conglomeratet0 the prone sliding geological structure.via gravity. From this assumption, we can concludethat the block is nearly rigid, and the theory of New-This peper is supported by the National Natural Science Foundetionton's second law is adopted to conduct the research in-of China (No. 40072084).to the block conglomerate movement and to simulateManuseript recived December 2], 2001.thep1l mass through theManuscript acepted January 25, 2002.micr中国煤化工is taken as discon-TYHCNMHG34An Guanfeng, Yin Kunlong and Tang Huimingtinuous media separated by cracks. Once the force ries (except the natural boundaries) are considered tosystem or boundary conditions in the block conglom- be fixed. The Bedong fault in the deep geology iserate change, the interaction force, including the specially included during the determination of geolog-branch force of gravity, may occur. Then the block ical model (Fig. 1). The calculation of the model iscan obtain some acceleration and displacements. The often associated with the stress field and the mecha-difference of displacements among the blocks can re- nism of the sliding formations under gravity. In ordersult in new interactions. The “overlap”among the to emphasize the sliding body, a magnified singleblocks can be used to describe the interaction using body is considered as a study region with 39 elementsthe discrete element method. The relationship be- and 60 nodes (Fig. 2).tween the force and displacement and the“overlap"displacement reveals that the new active force system BASIC PARAMETERS AND CALCULATION PRO-can be calculated. Furthermore, the new accelera- JECTtion, displacement and movement position can be ob-According to the reference ( Zhong et al. ，tained until the whole system reaches the balance 1992)， the normal stiffness coefficient kn is equal toagain and again (Wang and Xiong, 1992).the modulus of elasticity of rock mass. When the tan-gent stiffness coefficient k, is equal to sk.(0