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International Concrete Abstracts Portal

Showing 1-5 of 10 Abstracts search results

Document: 

SP83-08

Date: 

October 1, 1994

Author(s):

David W. Moller, Henry L. Minch, and Joseph P. Welsh

Publication:

Symposium Papers

Volume:

83

Abstract:

The Helms Pumped Storage Project is a new hydroelectric facility located in the Sierra Nevada mountains O f California. During excavation of the underground powerhouse complex, a previously unidentified shear zone was encountered in the granitic rock. The shear zone was a near vertical plane, up to 35 ft. in stratigraphic thickness, and was intersected by several tunnels near the powerhouse. During initial water filling of the power tunnel, the shear zone became a conduit for high pressure tunnel water (818 psi), allowing it to leave the power tunnel and seep into adjoining dry access tunnels. An innovative grouting program utilizing ultrafine cement (Blaine fineness of 8,880 cm /g) and pump pressures which were increased progressively with depth (up to 700 psi) was used to create a barrier between the pressure tunnel and the shear zone. The grouting program successfully reduced ground water pressures and seepage downstream of the barrier to acceptable levels. The program demonstrated the superior penetrating capability of grout made with ultrafine cement compared to type II and type III portland cement, and indicates that ultrafine cement grout can be an effective substitute for chemical grout when the properties of a cement grout are required.

DOI:

10.14359/6341


Document: 

SP83-01

Date: 

October 1, 1984

Author(s):

Pierre-Claude Aitcin, G. Ballivy, and R. Parizeau

Publication:

Symposium Papers

Volume:

83

Abstract:

Condensed silica fume is a by-product of the fabrication of silicon or ferrosilicon alloys. It is composed of very fine glassy spheres of quite pure silica having an average diameter of 0.1 pm. It is a very reactive pozzolan that has been found to increase drastically the compressive strength of concrete and to reduce significantly its permeability. The unique properties of condensed silica fume can also be used advantageously in grouts if condensed silica fume is used in combina-tion with a superplasticizer. The very fine silica particles give stability to the grout, there is no sedimentation of the cement particles and no bleeding. By adjusting the respective proportions of portland cement, of condensed silica fume,and of the superplasticizer a thixotropic grout can be made. The hardened grout is stronger and less porous when it contains condensed silica fume because the lime liberated during the hydration of portland cement reacts with the very fine silica particles to form a compact secondary CSH. By this way the possibility of leaching out of the lime is practically suppressed and the resistance of the grout to chemical attack should be improved.

DOI:

10.14359/6334


Document: 

SP83-05

Date: 

October 1, 1984

Author(s):

Robert M. Koerner, James D. Leaird, and Joseph P. Welsh

Publication:

Symposium Papers

Volume:

83

Abstract:

The detection and monitoring of subsurface flow phenomena, such as, seepage, grouting and hydrofracturing, are significant and largely unsolved problem areas. As a nondestructive testing technique, the acoustic emission (AE) method seems to be a likely candidate technique for application to these problems. This paper describes the AE method, in general, and a parti-cular AE system which holds significant promise in this regard. It is a multichannel AE system which will eventually source locate the emissions in three dimensions and in real time on a CRT screen. A series of laboratory tests, where equipment selection and proper system tuning were made, are described. Two field tests where chemical and cement grouts were being injected were also monitored with positive results, indicating the technical feasibility of the method. Computer software is presently being developed and, when complete, further field tests will be forthcoming.

DOI:

10.14359/6338


Document: 

SP83-06

Date: 

October 1, 1984

Author(s):

John G. Ruggiero

Publication:

Symposium Papers

Volume:

83

Abstract:

Tail void filling of soft ground shield driven tunnels has historically been conducted through the use of pea gravel and neat cement grout. This method has normally resulted in some settlement, infiltration of grout into utilities and divided the Engineer and Contractor on the question of how close to the tunnel heading grouting should be conducted. On the recently completed Red Hook Interceptor Sewer, a soft ground shield driven compressed air tunnel in New York City, a contract modification was made to use a low slump, 5-7 inches (12-18 cm), low shrink grout mixture of cement, limeflour, benton-ite and admixtures in lieu of pea gravel and neat cement grout. Placement was made at two to five times overburden pressures in close proximity to subsurface utilities and into the tail of the shield. Settlement monitoring indicated negligible settlement along the tunnel route. This paper describes the use and advantages of this method.

DOI:

10.14359/6339


Document: 

SP83-03

Date: 

October 1, 1984

Author(s):

Della M. Roy, M. Perez, B.E. Scheetz, and P.H. Licastro

Publication:

Symposium Papers

Volume:

83

Abstract:

Changes in length and volume of cementitious grouts for use in nuclear waste isolation have been investigated, and com-pared with the behavior of other mixtures, neat cement pastes, fly-ash containing mixtures, and mixtures with high-range water reducers (‘superplasticizers’). Expansive and non-expansive for-mulations are compared with respect to their changes in length and volume, both at atmospheric pressure and elevated curing condi-t ions, including those simulating placement under pressures of up to 1600 psi hydrostatic.

DOI:

10.14359/6336


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