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R.k. Goel - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of support pressure during tunnelling through Squeezing Grounds
    Engineering Geology, 2014
    Co-Authors: R.d. Dwivedi, Mahendra Singh, M.n. Viladkar, R.k. Goel
    Abstract:

    High in situ stresses and poor quality of rock mass are primarily responsible for the Squeezing behaviour of rock masses. This phenomenon is prevalent especially in the Himalayan region and hence rock engineers and engineering geologists have frequently encountered problems of stability during construction in this region. High in-situ stresses, poor rock mass quality, large overburden depth and large radius or span width of a tunnel or cavern in weak rocks are the factors which are responsible for the occurrence of Squeezing Ground Condition. The present study involves development of a dimensionally correct empirical correlation for assessment of support pressure in tunnels which are excavated in Squeezing Ground Condition. The correlation uses the concept of ‘joint factor’ as a measure of rock mass quality, allowable closure, depth and radius of opening as the governing parameters. Data from 52 different tunnel sections and one set of data from a mine gallery have been considered for analysis. The predicted results have been compared with the results obtained via existing approaches, based on rock mass quality (Q) and rock mass number (N). It was observed that the proposed correlation holds better with a correlation coefficient of 0.92 and estimated values of support pressure from the approach show better accordance with the observed values of support pressure as compared to other existing correlations based on Q and N values. The proposed correlation makes use of parameters which can be easily obtained at project sites. Therefore, it can become a handy tool for site engineers to predict the support pressure in Squeezing Ground Conditions and take appropriate measures for the stability of underGround excavations.

R.d. Dwivedi - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of support pressure during tunnelling through Squeezing Grounds
    Engineering Geology, 2014
    Co-Authors: R.d. Dwivedi, Mahendra Singh, M.n. Viladkar, R.k. Goel
    Abstract:

    High in situ stresses and poor quality of rock mass are primarily responsible for the Squeezing behaviour of rock masses. This phenomenon is prevalent especially in the Himalayan region and hence rock engineers and engineering geologists have frequently encountered problems of stability during construction in this region. High in-situ stresses, poor rock mass quality, large overburden depth and large radius or span width of a tunnel or cavern in weak rocks are the factors which are responsible for the occurrence of Squeezing Ground Condition. The present study involves development of a dimensionally correct empirical correlation for assessment of support pressure in tunnels which are excavated in Squeezing Ground Condition. The correlation uses the concept of ‘joint factor’ as a measure of rock mass quality, allowable closure, depth and radius of opening as the governing parameters. Data from 52 different tunnel sections and one set of data from a mine gallery have been considered for analysis. The predicted results have been compared with the results obtained via existing approaches, based on rock mass quality (Q) and rock mass number (N). It was observed that the proposed correlation holds better with a correlation coefficient of 0.92 and estimated values of support pressure from the approach show better accordance with the observed values of support pressure as compared to other existing correlations based on Q and N values. The proposed correlation makes use of parameters which can be easily obtained at project sites. Therefore, it can become a handy tool for site engineers to predict the support pressure in Squeezing Ground Conditions and take appropriate measures for the stability of underGround excavations.

Mahendra Singh - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of support pressure during tunnelling through Squeezing Grounds
    Engineering Geology, 2014
    Co-Authors: R.d. Dwivedi, Mahendra Singh, M.n. Viladkar, R.k. Goel
    Abstract:

    High in situ stresses and poor quality of rock mass are primarily responsible for the Squeezing behaviour of rock masses. This phenomenon is prevalent especially in the Himalayan region and hence rock engineers and engineering geologists have frequently encountered problems of stability during construction in this region. High in-situ stresses, poor rock mass quality, large overburden depth and large radius or span width of a tunnel or cavern in weak rocks are the factors which are responsible for the occurrence of Squeezing Ground Condition. The present study involves development of a dimensionally correct empirical correlation for assessment of support pressure in tunnels which are excavated in Squeezing Ground Condition. The correlation uses the concept of ‘joint factor’ as a measure of rock mass quality, allowable closure, depth and radius of opening as the governing parameters. Data from 52 different tunnel sections and one set of data from a mine gallery have been considered for analysis. The predicted results have been compared with the results obtained via existing approaches, based on rock mass quality (Q) and rock mass number (N). It was observed that the proposed correlation holds better with a correlation coefficient of 0.92 and estimated values of support pressure from the approach show better accordance with the observed values of support pressure as compared to other existing correlations based on Q and N values. The proposed correlation makes use of parameters which can be easily obtained at project sites. Therefore, it can become a handy tool for site engineers to predict the support pressure in Squeezing Ground Conditions and take appropriate measures for the stability of underGround excavations.

M.n. Viladkar - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of support pressure during tunnelling through Squeezing Grounds
    Engineering Geology, 2014
    Co-Authors: R.d. Dwivedi, Mahendra Singh, M.n. Viladkar, R.k. Goel
    Abstract:

    High in situ stresses and poor quality of rock mass are primarily responsible for the Squeezing behaviour of rock masses. This phenomenon is prevalent especially in the Himalayan region and hence rock engineers and engineering geologists have frequently encountered problems of stability during construction in this region. High in-situ stresses, poor rock mass quality, large overburden depth and large radius or span width of a tunnel or cavern in weak rocks are the factors which are responsible for the occurrence of Squeezing Ground Condition. The present study involves development of a dimensionally correct empirical correlation for assessment of support pressure in tunnels which are excavated in Squeezing Ground Condition. The correlation uses the concept of ‘joint factor’ as a measure of rock mass quality, allowable closure, depth and radius of opening as the governing parameters. Data from 52 different tunnel sections and one set of data from a mine gallery have been considered for analysis. The predicted results have been compared with the results obtained via existing approaches, based on rock mass quality (Q) and rock mass number (N). It was observed that the proposed correlation holds better with a correlation coefficient of 0.92 and estimated values of support pressure from the approach show better accordance with the observed values of support pressure as compared to other existing correlations based on Q and N values. The proposed correlation makes use of parameters which can be easily obtained at project sites. Therefore, it can become a handy tool for site engineers to predict the support pressure in Squeezing Ground Conditions and take appropriate measures for the stability of underGround excavations.

Goel R. K. - One of the best experts on this subject based on the ideXlab platform.

  • Effect of shape of underGround openings on boundary stresses
    'Elsevier BV', 2004
    Co-Authors: Goel R. K.
    Abstract:

    As soon as an underGround excavation is made, the in situ stresses with in the rock mass gets disturbed and redistribution of stresses takes place. As such, the stresses around an underGround opening would be different from the pre-excavation stresses, i.e., in situ stresses. A zone of disturbed stresses is formed around an opening and generally known as ‘zone of influence’. The extent of zone varies from rock to rock. For a very good and strong rock this zone is small, where as for weak rocks it is large. In other words, if the induced stresses due to tunnelling do not exceed the in situ strength of the rock mass, the surrounding rock mass remains in an elastic state and the zone of influence is limited. However, when the induced stress is more than the strength of the rock mass, the rock fails and the Condition is popularly known as Squeezing Ground Condition. The boundary stresses around an underGround opening govern the stability of underGround opening. It has been studied by Hoek and Brown (1982) that the shape of underGround opening does affect the boundary stresses around an underGround opening. To carry forward the work, a Research Project was awarded to the author by Ministry of Water Resources, Government of India. Parametric study has been carried out to obtain the influence of shape of underGround openings on maximum boundary stress. In addition to five different shapes of the opening, various other parameters used for the study are tunnel depth, in situ stresses, uniaxial crushing strength of intact rock material, and Bieniawski’s rock mass rating. The analyses for various values of all these parameters have been performed using numerical analysis code FALC3D. The maximum boundary stresses at the roof have been obtained and simple equations are developed for estimating the maximum boundary stresses. The analysis shows that the curves for horse-shoe and circular shapes are almost superimposing indicating that the roof stresses at the centre of the opening in these two shapes are almost same. Using the equations, maximum boundary stress can be estimated. Using the failure criterion of Sheorey (1997), safety factor contours for all the models have been plotted and the minimum safety factor values (fmin) at the roof have been obtained. Using fmin, in situ stress ratio k, depth of underGround opening, rock mass rating RMR and laboratory crushing strength, rc, finally different equations have been developed for each shape to estimate the minimum factor of safety value in the roof of the opening