Abstract

A generalised ground model with geotechnical characterisation has been developed for the city of Doha, in Qatar, combining a wide range of ground investigation data and observations during the construction of projects that WS Atkins & Partners Overseas were involved with. The model proposes a geotechnical characterisation and ranges of parameters for the main units found at depths relevant to civil engineering activities. A geotechnical classification system is proposed to differentiate the Simsima Limestone subunits encountered on site, based on rock quality designation (RQD) values and weathering degree. The proposed classification system and the relevant geotechnical parameters have been validated during construction. The construction of all excavations, temporary retaining systems and tunnel excavations that rely on the information presented in this paper has been completed successfully. This confirmed a reasonable agreement between the theory presented in the paper and the practical conditions encountered on site. Best site investigation practices are discussed with highlights on difficulties encountered on site and how they were resolved. RQD and rock mass rating values were found to produce a good representation of the ground conditions while the applicability of the geological strength index classification is believed to be limited.

Highlights

  • The available literature on the geological and geotechnical setting in the city of Doha, the capital of Qatar, is limited

  • If the different zones are small compared to the project/structure, one rock mass rating (RMR)/geological strength index (GSI) value may be considered for the whole rock mass, whereas in a different case, a different value should be considered for each zone

  • The hydrogeological units encountered at depths where most civil engineering works are constructed are typically a perched aquifer in the Quaternary deposits, an unconfined aquifer in the Simsima Limestone Formation, an aquitard in the Midra Shale Formation and an underlying partially confined aquifer in the Rus Formation

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Summary

Sainath Reddy Mulinti MEng

A generalised ground model with geotechnical characterisation has been developed for the city of Doha, in Qatar, combining a wide range of ground investigation data and observations during the construction of projects that WS Atkins & Partners Overseas were involved with. A geotechnical classification system is proposed to differentiate the Simsima Limestone subunits encountered on site, based on rock quality designation (RQD) values and weathering degree. The construction of all excavations, temporary retaining systems and tunnel excavations that rely on the information presented in this paper has been completed successfully. This confirmed a reasonable agreement between the theory presented in the paper and the practical conditions encountered on site. RQD and rock mass rating values were found to produce a good representation of the ground conditions while the applicability of the geological strength index classification is believed to be limited

Introduction
Geological setting
Geology and geotechnical evaluation of
Rus Limestone Formation Rus Limestone Formation Rus Gypsum Formation
Rus aquifier water table
Geotechnical hazards
Simsima Limestone Formation proposed geotechnical classification system
Simsima Limestone
Cobble partially affected by weathering
Geotechnical parameters
HWSL MWSL SWSL SL MS RFL RUS GYP
Applicability of rock classification methods RMR and GSI
Particle size analysis
In situ physical testing
Ground investigation techniques
CONSIDERATIONS WHEN CONDUCTING FALLING HEAD TESTS IN THE DOHA ROCK FORMATIONS
PACKER AND FALLING HEAD TESTS IN UNSATURATED GROUND
COMMON FACTORS COMPROMISING THE VALUE OF PUMPING TESTS IN DOHA
IDENTIFICATION OF HIGH WATER FLOW FRACTURES
Conclusions
Findings
Recommendations for further work

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