Geotechnical monitoring and risk assesment

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Geotechnical investigation and risk assessment at
Budapest metro line 4
INTERNATIONAL SOCIETY FOR SOIL MECHANICS AND
GEOTECHNICAL ENGINEERING HUNGARIAN NATIONAL
COMMITTEE

• Dr. Tibor Horváth
• Geovil Ltd.

24th -25th September 2010, Budapest ISSMGE TC 302
Failures, Disputes, Causes and Solutions in
Geotechnics
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MAIN FEATURES OF METRO LINE 4

• Length of line 12.7 km
• Phase I 7.4 km
• Phase II 3.2 km
• Phase III 2.1 km
• Number of stations 16
• Phase I 10 stations
• Phase II 4 stations
• Phase III 2 stations
• Extensions
• Phase II currently holds licences from both
  railway and environmental authorities as far as
  Bosnyák tér, while the planned Phase III would
  extend as far as the Budaörs Flower Market.

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The route proceeds at a relatively shallow depth,
at a rail-top level of 16-22 metres below the
surface on average, the depth of 32-34 metres
under the Danube, passing beneath an almost
entirely built-up area and through extremely
varied geological strata.
Buda section
Danube
Pest section
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Enginner geological profile of Buda side
Kiscelli marly clay stone, weathered
Kiscelli marly clay stone, fissured
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Engineering geological profile of river Danube
crossing
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Engineering geological profile of Pest side
Pleisztocene, river sediments
Miocéne, litoral facies of of a mediterrain sea
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Risk Classification by Likelihood L
1 Frequent An effect derived in the frame of a survey from any risk successively experienced/monitored during the project and supported statistics derived, if applicable, from the project and other relevant events.
2 Likely An effect derived in the frame of a survey from any risk often experienced/monitored during the project and supported statistics derived, if applicable, from the project and other relevant events.
3 Occasional An effect derived in the frame of a survey from a risk occasionally experienced/monitored during the project and supported statistics derived, if applicable, from the project and other relevant events.
4 Unlikely An effect derived in the frame of a survey from an unlikely risk during the project and supported statistics derived, if applicable, from the project and other relevant events.
5 Improbable An effect derived in the frame of a survey from an improbable risk often experienced/monitored during the project and supported statistics derived, if applicable, from the project and other relevant events.
Risk Classification by Severity S
1 Catastrophic Several immediate or deferred fatality cases attributable to injuries or illness. Loss of production for more than seven days. (Total loss 5 millions)
2 High A single immediate or deferred fatality case attributable to injuries or illness. Loss of production of one to seven days due to damage to work or equipment. (Total loss above 1 million, but below 5 millions)
3 Significant Injury, illness or dangerous circumstance subject to reporting. The loss of production due to injury exceeds one shift. Max. one days loss of production due to damage to work or equipment. (Total loss of more than 25,000 but less than 1 million)
4 Low Minor injury. No loss of time or the person can return, after receiving medical attention, to work yet in the same shift. Damage not causing a significant delay in work performance or equipment. (Total loss of max. 25,000)
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Risk Assessment Classification Matrix RI (Risk
Index)
Risk Severity / Likelihood 1 Catastrophic 2 High 3 Significant 4 Low
1 Frequent 1 2 3 4
2 Likely 2 4 6 8
3 Occasional 3 6 9 12
4 Unlikely 4 8 12 16
5 Improbable 5 10 15 20
Risk Index, Classification and Marking
Risk Index (R) Risk classification Marking
1 4 Very high V (Very high)
5 9 High H ( High )
10 14 Medium M (Medium)
15 29 Low L (Low)

• After determining the likelihood and severity
  of the risk we determined the risk index by means
  of the assessment
• matrix.
• Risk index Likelihood of occurrence x Severity
  of risk
• RI L x S
• The risk index has been calculated for the
  starting/initial cases and the cases yet
  remaining despite the efforts
• made to alleviate severity of the risks
  involved.

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Elements of Risk Assessment Arise from Geology,
Hydrogeology and Geotechnical features

• General risk from the level of geotechnical
  investigation,
• Personal risk
• Third party risk
• Environmental risk
• Risk of equipments
• Risk of program and delay

Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall Annex "A1." Geotechnical risk level matrix table of Rákóczi Square Station with the section to be built by installing a diaphragm wall
Initial conditions, risks Initial conditions, risks Initial conditions, risks Initial conditions, risks Initial conditions, risks Residual conditions, risks Residual conditions, risks Residual conditions, risks Residual conditions, risks Residual conditions, risks  
Risk L S RI RR Reduction L S RI RR Comments
GENERAL RISK FROM THE LEVEL OF GEOTECHNICAL SURVEYING                    
The geotechnical and hydrogeological data available for the preparation of working drawings and for construction are not reliable and insufficient. 2 1 2 V Supplementary geotechnical and hydrogeological surveys. Continuous geotechnical service during construction. 4 4 16 L In order to reduce risk, we suggest 2 "dry land" bores and a hydrogeological survey.
The supplementary geotechnical surveys are not suitably assessed. 4 3 12 M Consultation with the specialist geotechnical service, continuous presence of the specialist service during construction. 5 4 20 L The geotechnical specialist service maps the strata found during excavation continuously and provides information about it to construction management.
River water level 0.5 m higher than the highest flood level of the Danube. 3 3 9 H During the preparation of construction drawings, protection shall be planned. Continuous assessment of water level reports, a technical and personnel protection plan shall be prepared. 4 4 16 L  
Groundwater level exceeds the estimated nominal design level 2 3 6 H Continuous monitoring and evaluation of data from groundwater monitoring wells and the Danube water levels. Preparation of a technical and personnel plan for protection against high groundwater levels. 4 4 16 L  
Soil and rock conditions differ from those established by the supplementary geotechnical survey. 3 4 12 M Consultation with the specialist geotechnical service and the designer, additional geotechnical and hydrogeological tests and surveys to be performed as required. 4 4 16 L  
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Geotechnical general risk from the level of
geotechnical investigation, at Buda
side
After additional investigation and monitoring
At the time of GBR
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Geotechnical General Risk from the Level of
Geotechnical Investigation, at Danube River
Crossing
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Geotechnical General Risk from the Level of
Geotechnical Investigation at Pest side
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Volume of Geotechnical Investigation
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Total Volume of the Investigation at the End of
Construction Work
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Length of boring versus length of tunnel
(stations with SCL method)
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Length of boring versus boring length / tunnell
length
Length of boring (m)
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Length of boring versus length of tunnell
Recommended rate of USTNC/TT1,2
U.S. National Committe on Tunnelling
Technology, 2005
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Cost of geotechnical investigation / cost
construction at SCL tunnells
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Budapest metro 4, Kelenföld station, portal land
slip
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Budapest metro 4 Fovám station
Due to the detailed investigation and monitoring
the tunneling work has been safe and successful
in very dangerous difficult geotechnical
conditions.
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Budapest metro 4 Rákóczi station SCL tunnell
collapse wash out
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Budapest metro 4 Rákóczi station SCL tunnell
collapse wash out
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Budapest metro 4 Rákóczi station SCL tunnell
collapse wash out
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Budapest metro 4 Rákóczi station SCL tunnell
collapse wash out
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Budapest metro 4 Rákóczi station SCL tunnel
collapse wash out
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Conclusions and recommendations

• The Geotechnical Risk Assessment comes from a
  suitable site investigation and the consequent
  building of an appropriate and coherent
  Engineering Geological model.
• It is desirable to create an international
  standard for the Geotechnical Risk Assessment,
  and to agree the parameters and guidelines for
  these recommendations.
• The Geotechnical Risk Assessment has a
  relationship to the quantity of meters of site
  investigation holes bored and the excavated
  length of tunnel. For the SCL tunnel ( soft
  tunneling at shallow depth ) the ratio of site
  investigation / excavated tunnel length should be
  1.2 .
• For the Budapest metro 4 project, the recommended
  ratio was followed. This resulted in a project
  which was very safe, in geological, geotechnical
  terms also the project had very few disputes
  related to the geotechnical risk clauses

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• Thank you for your kind attention!