Engineering classification of soil masses for design of tunnel support based on observations in Tehran eastern main sewerage tunnel

Abstract

The need to provide an index of subsurface soil behaviour which would include allowances for intact soil strength, soil texture and its matrix properties, discontinuity frequency, groundwater condition together with stress condition at the depths encountered has led this author to develop a soil mass classification system to isolate in a qualitative manner categories of soil which, under a particular set of engineering constraints, will behave in a similar way. The principle on which this classification system is based is that the selected parameters which are important in determining soil mass behaviour can be determined quickly and easily by a field geologist or engineer. For a particular soil stratum, a numerical assessment is made within designated limits of the quality of the soil as it relates to a particular parameter. These numbers are then summed to give an index number which can be related to the behaviour of soil mass culminating in the prediction of excavation procedures and support system density for a 3⋅5 m diameter hand excavated tunnel. The classification provided very good feed-back for the NATM tunnelling method, including stand-up time and support requirements.

Keywords

Tehran alluviums Soil index parameters Support and excavation details in shallow tunnels

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References

Assereto

, Dellenbach

, Nabavi

M. H.

, Engalence

and Vahdati-Daneshmand

1999. Geological map of Tehran (scale: 1:100,000), Geological Survey of Iran, Sheet no. 6361.

Berberian

, Qarashi

, Arzhang-Ravesh

and Mohajer-Ashjaei

1985. Research and deep investigation on neotectonics, seismotectonics and fault-rupture hazard in Tehran and surrounding area, Geological Survey of Iran, Report no. 56 (in Persian).

Bieniawski

Z. T.

1976. Rock mass classifications in rock engineering, Proceedings of symposium, exploration rock engineering, Johannesburg, Balkema, Cape Town, Rotterdam Vol. 1, 97–106.

Casagrande

1948. Classification and identification of soils, Trans. Am. Soc. Civ. Eng., 113, 901–930. (New York, Paper no. 2351).

Casagrande

1965. Role of the calculated risk in earthwork and foundation engineering, J. Soil Mech. Found. Div., 91, (SM4) pp. 1–40.

Deere

D. U.

1968. Geological considerations, in Rock mechanics in engineering practice, (eds. Stagg

K. G.

and Zienkiewicz

O. C.

), 1–20, London, Wiley.

Handy

R. L.

1973. Stability problems of collapsing soils, J. Soil Mech. Found. Div., 93, 577–594.

Lauffer

1958. Gebirgsklassifizierung fur den Stollenbau, Geol. Bauw., 24, 46–51.

Skempton

A. W.

1944. Notes on the compressibility of clays, Q. J. Geol. Soc. London, 100, 119–135.

10.

Terzaghi

1946. Rock defects and loads on tunnel supports. In Proctor R.V. and White, T. Rock tunnelling with steel supports. Youngstown, Ohio, Commercial Shearing and Stamping Co., 15–99.

11.

Terzaghi

and Peck

R. B.

1967. Soil mechanics in engineering practice, London, John Wiley and Sons.