| This article based on "the study on the geological survey and stability evaluation project of Erguxi deformation boday at Shiziping hydropower station" project, the dumping of Erguxi deformation as the research object, by collecting the original geological data, using the means of field geology survey(surface survey, drilling, logging, and adit catalog and field monitoring) and combining with the engineering geological analysis method to establish the geological model of complete; According to the deformation characteristics of slope form and development of "sabre tree" characteristics, analyzed the history and present of the slope’s stage of deformation; By means of adit catalog to do the toppling slope rock mass classification, in fully grasp the toppling slope geological prototype, rock mass structure combination, using limit equilibrium calculation and numerical simulation methods to analyze dump deformation deformation stability, and we ge the following several main conclusions:(1)Erguxi toppling slope is mostly covered by quaternary deposits, only a few of the bedrock exposed, the cover layer from top to bottom can be divided into two parts: Gravelly soil and With the rock broken gravel soil, the overlying bedrock is metamorphic sandstone of Middle Triassic(T2z) with phyllitic slate,(T2zh) phyllitic slate and metamorphic sandstone, most of the bedrock is broken, the toppling deformation phenomenon is obvious.(2)The deformation of Erguxi tunnel is more serious, for To investigate the situation of tunnel deformation by means of 3D laser scanning, It was found that the deformation of tunnel displacement maximum reached above 1m, Through the displacement and stress calculation we analysised the stress of tunnel, Because the tunnel deformation seriously failed to continue to use after maintenance.(3)The idea that using the rose diagram of joint, We obtained the bending direction of the bent advantage tree is about 220 degree. The appearance of bending morphology of trees, can not only reconstruct the landslide deformation history, but also to indicate the current state of the landslide movement. Most the bent tree on the landslides have only one times was bent, indicating that the growth in the period of bent tree had only one obvious sliding; new and old tree branches were slightly inclined toward the lower slope angle, showed that the two ancientlandslide is now once again in the sliding deformation. In the Erguxi toppling landslide area, there are around with bent tree, pine diameter bending phenomenon does not appear to statistics about 15 cm. Therefore, according to the previous experience formula to estimate the last significant sliding time is about 45 years ago.(4)The Erguxi toppling slope is in Zagunao River Valley in the shape of "V", The two sides steep bank slope, in the sky condition is very good, The lithology of the soft and hard interphase phyllitic slate layer and Thin to medium thick bedded metamorphic sandstone, The valley is oblique Valley, slope is the reverse of steep layered slope, slope structureprone to toppling deformation; In "5.12" and "4.20" for the two time of big earthquake, made the toppling rock slope further damaged, then with the rainfall infiltration andgroundwater reservoir, exacerbating the toppling deformation of slope. The internal reason made the Erguxi slope deformation in slope structure, topography and lithology, and the external factor is the comprehensive effect of the various factors, showing the "slope excavation transformation + seismic damage + continuous transformation, watersoftening + rainy season weakening slope toppling deformation mechanism of creep crack" in the process of.(5) According to the geological conditions and deformation characteristics of the different, the Erguxi toppling slope will be divided into strong deformation area and weak deformation zone of Aand B. And then we divided A area into 3 sub zones, A1 and A2 zones’ s deformation were stronger than A3. B area of deformation is not obvious, there is no obvious signs of deformation of surface survey, only in the 2# tunnel upstream hole lateral retaining wall of highway slightly bulging, trailing vaguely that several has not been through the small cracks.(6)The monitoring results show that the two ancient Creek deformation is still slow deformation.A1 sub zones’ s main defomation was to surface and sink, but there are also differences in the partitioning of deformation.By the data of displacement monitoring, we can find that the deformation was mainly due to the influence of water storage and water storage, and have a positive linear correlation with the retain water.(7)Through surface geological investigation, drilling and hole exploration and analysis of monitoring data, we find that: in A1 zone the slope’s cover, inside the base cover interface and found no internal bedrock sliding surface continuous weak layer or through the front cover, bedrock layer, toppling deformation strongly, downstream displacement vector phase back, deformation difference.That is still in the deformation stress adjustment, expansion has not been the disintegration of the creep coordination of slow deformation, that the slope is most likely the potential instability mode is broken along the loose zone or toppling bottom boundary damage, rainstorm, earthquake and long-term factors in reservoir induced factors such as hair, will have a certain scale of slope failure.A2 zone of slope is mainly composed of Zagunao group metamorphic sandstone and slate toppling deformation strongly, suggested that the most likely deformation mode should be broken along strong toppling deformation zone bottom deformation is formed through the weak plane, and then become a predisposing factor in the long-term slip failure, rainstorm, earthquake and reservoir etc. there are some factors of instability and failure may scale.A3 zone is faint signs of deformation, in addition to the main trailing edge crack, longitudinal crack was not found, analysis to determine the area is still in the stage of creep, the overall situation is basically stable.B area of deformation is not obvious, the trailing edge of a plurality of vaguely that has not been through the small cracks, analysis in creep stage, the overall situation is basically stable.(8)Through calculation and analysis: A1 area’s front was in the critical stable state under the natural condition, while the normal water level is 2540 m, and the normal water level drawdown of water level 2540 m with earthquake(VII) under the condition of the slope stability coefficient K is less than 1, the slope is critical to less stable state, the minimum safety factor of reservoir area can not meet the requirements of B2 grade of slope; A1 area were stable in natural conditions, and in the normal water level is 2540 m, the normal water level of 2540 m with earthquake(VII) under the condition of the slope stability coefficient K is less than 1.05, the minimum safety factor requirements the reservoir can not meet the B2 grade of slope. A2 area werestable in natural conditions, and in the normal water level of 2540 m, 2540 m with normalimpoundment earthquake(VII) under the condition of the slope stability coefficient K is less than 1.05, the minimum safety coefficient can not meet the requirements of B 2 grade of slope. B area were stable in natural conditions, and in the normal water level of 2540 m, 2540 m with normalimpoundment earthquake(VII) under the condition of the slope stability coefficient K = 1.05, minimum safety coefficient satisfies the B2 grade of slope.(9) The surface geology survey shows that deformation through basic body edge cracks, drilling, adit exploration revealed a soft surface or sliding surface continuous were not found in slope, deformation monitoring data shows that the slope was in the slow deformation, and the deformation characteristics of different partition. In view of the deformed body found no unified penetrating soft surface, the direction of deformation in different parts of the slope are not consistent, so the Erguxi deformation body whole failure possibility of rapid loss of small, but do not rule out the role of rainstorm, earthquake and reservoir factors may leading a small scale of the slope failure. |
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