| The5.12Wenchuan earthquake has the characteristics of high magnitude,shallow seismic source, planer seismic source, having a300m long fracture zone,9kmmaximum slipping-off momentum, long earthquake duration and strong groundseismic response. The Daguangbao landslide in Anxian, Gaochuan is a giant rockylandslide which has a volume of about1.1billion m3and a690m tall barrier dam, thislandslide was triggered by the Wenchuan earthquake. It has unique features such ashigh and steep pull crack wall in the back edge, the long huge cracking surface in theupstream of the landslide, the side crack boundary in the downstream, the slip masscasted towards Menkanshigou in the air, the “breaking effect” of the main slip mass inthe Huangdongzi groove） and so on.What attract the scholars most is the feature that the downstream side cracksurface’s fragmentation and brecciation occur after the consequent bedding rocklandslide.This thesis is based on field surveying and mapping, field drilling core test,borehole wae velocity test, borehole TV, the test and analysis about the rock fromsliding zone, indoor rock mass physical mechanical and dynamic tests. Afterresearching the Daguangbao slip mass’s fragmentation, our work and results obtainthe basic conclusions and the knowledge as follows:(1)The slip rock mass-Sinan Dengying Formation(Zd3) dolomite-is affected bymultiphase tectonic activities, It’s cleavage has developed, rock mass is sheared andbroken, mechanical properties is poor. All the above constitute the material base ofrock mass fragmentation.(2)The miscroscopic characteristics of microstructure of slip rock mass showsthat the rock sample presents fine grained seriate irregular columnar structure andastatic block structure. Rock constituents are all consists of carbonate minerals. Theseminerals have a grain size between0.02~0.04mm, present irregular columnarstructure and astatic distribution.Because of these, they form irregular crisscrosscombined column structure. The structure is relatively homogeneous and irregularcleavage developed well. (3)The gain size analysis test of the slip rock mass show that fragmental rock ismainly consist of breccias, also there are gravel and adhesion gravel in it.(4)Fragmentation of slip rock mass has the effect of elevation control, theamplification effect of terrain, the direction effect of fragmentation.(5)We carried out the statics and dynamics test on the slip rock mass, SinanDengying Formation(Zd3) dolomite is brittle rock with few plastic deformation, itresponse strongly to the dynamic load; Devonian Shawozi Formation(Ds) dolomitepresents plasticity and clearly yielding characteristic. Acoustic emission curverecorded the acoustic features of the whole process of rock burst..(6) Fragmentation of slip rock mass has second stage characteristics: The slipzone rock is effected by the seismic waves before the “locking section” was shearedto be fractured, it causes the fatigue breakages of the rock. After the fatigue loading,cracks appeared and developed inside the slip rock mass, formed the bursting phase ofrock mass’s rupture surface. After the “locking section”, landslide slides, slip masswill occur vibration and shear sliding of sliding surface, the surface begin to fluctuate,appears irregular condition. With the movement of the slip mass, the rock will occurtensile fracture and will be crushed, these make the rock fragmentation happen.(7)In a certain depth of the slip zone, the rock mass begin to appear fragment,brecciated and sandification.It makes fresh rock mass’s physical and mechanicaldecrease significantly, such as the decrease of the density and the shear strengthparameter, they can reduce the quality of the rock mass. The slip zone has the effect ofrolling friction, the effect improves the movement of slip mass, the moving slip masswill further press the rock, until the landslide being stopped by the accumulation. |
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