Engineering Geology of Dillon Dam, Spillway Shaft, and Diversion Tunnel, Summit County, Colorado

SHEARD CLAYEY SHALES OF FLYSCH. THEIR BEHAVIOR DURING THE EXCAVATION OF THE DIVERSION TUNNEL OF GADOURA DAM IN RHODES (GREECE)

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16637 ◽

2004 ◽

Vol 36 (4) ◽

pp. 1773

Author(s):

Π. Μαρίνος ◽

T. Χριστοδουλοπούλου ◽

Β. Περλέρος

Keyword(s):

Engineering Geology ◽

Groundwater Table ◽

Fiber Glass ◽

Pressure Relief ◽

Tunnel Face ◽

Diversion Tunnel ◽

Geotechnical Parameters ◽

Temporary Support ◽

The Face ◽

Geological Formation

This paper deals with the particular geological-geotechnical conditions that predominate in the construction area of the diversion tunnel of Gadoura dam (in Rhodes) and the way these conditions were taken under consideration during the construction of the temporary support system. The intensely sheared geological formation of flysch that is encountered in the construction area of the tunnel, is characterised by the predomination of clayey shales against siltstones and other lithological members (sandstone horizons, occasional gypsum lenses and limited limestone intercalations) and by the absence of a groundwater table. The main features of this argillaceous facies of flysch are: the schistosity-foliation due to tectonic compression and the chaotic structure, in places where it occurs in alternations with sandstone and siltstone, due to differential deformation of the strata. As a result, squeezing phenomena occured during the tunnel advance. According to the engineering geology model, which was proposed after the first excavation works, sheared clayey shales compose a "soil type" rockmass specified by very low geotechnical parameters (GSI=15-20, ITIJ=6, Oci=5-10 MPa, E m =30r>500 MPa, c'=150+250 kPa, φ=13°+18° και oCm=0,400,60 MPa). Performing a declined surface on the tunnel face, shotcrete and fiber glass anchoring, this weak rockmass was behaved well on the face. The applying of a light forpoling system has contributed to the stabilization of the face and of the cylindrical "core" of rock immediately ahead of the advancing face, although it was a conservative measure. Steel ribs incorporated into shotcrete were used for the support of the tunnel behind the face. Lateral forces were further stabilized by the closure of the invert using reinforced concrete. Weep holes were locally opened for the pore pressure relief.

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Analysis of Features and Causation of Rock Burst of Qirehataer Diversion Tunnel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.256-259.1243 ◽

2012 ◽

Vol 256-259 ◽

pp. 1243-1246

Author(s):

Shu Wen Chen ◽

Guo Bin Zhao ◽

Xiang Min Chen ◽

Hao Wang

Keyword(s):

Rock Burst ◽

Engineering Geology ◽

In Situ Stress ◽

Paper Analysis ◽

Underground Engineering ◽

Diversion Tunnel ◽

The Maximum Principle ◽

Gneiss Granite ◽

Brittle Rock Mass

Rock burst will happened when the underground engineering is excavated in the hard and brittle rock mass because of high in situ stress or concentrated stress. The length of Qirehataer diversion tunnel is 15.639km,and the maximum over-depth is 1720m. With excavation of tunnel, lightly to moderate rock burst had taken place in 600m length about of tunnel, and moderate rock burst locally. The mainly lithology of tunnel is gneiss granite and the percent is 64.5%, uniaxial compressive strength of which is 63.5MPa so it should be classified hard rock. The maximum principle stress is 30MPa in the place of rock bust. This paper analysis engineering geology conditions of this area and the characters of rock burst, author concludes that posteriority and continuity for time and Traceability and continuity for place are different from others rock burst examples. The reason is that course of stress adjustment is continually and repetitive.

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