Estimation of Allowable Bearing Capacity of Basement Rock

We have a location where a Standard Penetration Test (SPT) has been done up to 22m below the ground level, and additional 8m coring in weathered rock, with "ZERO" Rock Quality Designation (RQD) values, when the Client ordered termination of boring.

How can we estimate the allowable bearing capacity of this rock? Is carrying out Uniaxial Compressive Strength (UCS) test, the only possible method?

Many thanks in advance.

Rock Mechanics Design Deep Foundations

Asked 17/03/2018 15:08, updated: 26/07/2018 19:12

Kassapa Gamlath

3 Answers

Votes: 1

Abdul Jabbar

03/07/2018 03:50 *

You may perform point load tests on the rock material and u can correlate it with Ucs value. The angle of repose can be consider in calculating allowable bearing capacity.The Angle of Repose because Rock Triaxial instruments are rarely available in the local industry. Further reading is recommended on intermediate Geo-Materials ”IGM

Votes: 1

Done Nikolovski

03/07/2018 03:50 *

Bowles (fifth edition, p279) suggests that you can make calculation of the bearing capacity of the ground, according to the same equations that are derived for soil materials, when you have value of RQD<25. Make the best estimation of the parameters of the ground (fi and C), for the given stress state.

Regards

Votes: 0

Louai Jannoun

26/07/2018 19:12

Hello
If rqd is zero. Then very poor rock. As engineering judgement i would consider this rock as very dense gravel with low or zero cohesion and high angle of internal friction.

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Estimation of Allowable Bearing Capacity of Basement Rock

3 Answers

Abdul Jabbar

Done Nikolovski

Louai Jannoun