Table Recommendations of Singh et al. (1995) on support pressure for rock tunnels and caverns. Terzaghi’s classification Classification of Singh et al. (1995) Recommended support pressure (MPa) Category Rock condition I. II. III. IV. V. Hard and intact Hard stratified or schistose Massive, moderately jointed Moderately blocky seamy and jointed Very blocky and seamy, shattered arched Completely crushed but chemically intact Rock load factor Hp Category Rock condition 0 0 to 0 to to (B + Ht ) to (B + Ht ) I. II. III. IV. V. Hard and intact Hard stratified. | Table Recommendations of Singh et al. 1995 on support pressure for rock tunnels and caverns. Terzaghi s classification Classification of Singh et al. 1995 Recommended support pressure MPa Category Rock condition Rock load factor Hp Category Rock condition Pv Ph Remarks I. Hard and intact 0 I. Hard and intact 0 0 - II. Hard stratified or schistose 0 to II. Hard stratified or schistose 0 - III. Massive moderately jointed 0 to III. Massive moderately jointed 0 - IV. Moderately blocky seamy and jointed to B Ht IV. Moderately blocky seamy very jointed Pv Inverts may be required V. Very blocky and seamy shattered arched to B Ht V. Very blocky and seamy shattered highly jointed thin shear zone or fault Pv Inverts may be required arched roof preferred VI. Completely crushed but chemically intact B Ht VI. Completely crushed but chemically unaltered thick shear and fault zone pv Inverts essential arched roof essential continued Terzaghi s rock load theory 33 Table Continued Terzaghi s classification Classification of Singh et al. 1995 Recommended support pressure MPa Category Rock condition Rock load factor Hp Category Rock condition Pv Ph Remarks VII. Squeezing rock at to B Ht VII. moderate depth VIIA. VIIB. Squeezing rock condition Mild squeezing ua a upto 3 Moderate squeezing ua a 3 to 5 Depends on primary stress values Ph may exceed pv As above Inverts essential. In excavation flexible support preferred. Circular section with struts recommended. As above VIII. IX. Squeezing rock at to B Ht VIIC. great depth Swelling rock upto 80 m VIII. VIIIA. VIIIB. VIIIC. High squeezing ua a 5 Swelling rock Mild swelling Moderate swelling High swelling As above Depends on type and content of swelling clays Ph may exceed Pv As above As above As above Inverts essential in excavation arched roof essential. As above As .
