RISK ASSESSMENT FCC. draft, 2. September 2015

Transcription

1 RISK ASSESSMENT FCC draft, 2. September 2015

2 risk assessment in an early stage of the project what do we know general ground conditions composition of the rock mass orientation of the rock layers discontinuities in the different rocks (, karst ) existence and level of the groundwater 2

3 risk assessment in an early stage of the project what do we know possible construction methods pile and diaphragm walls for shafting shaft sinking machines machine supported excavation and rock safety measures in soft and hard rocks conventional rock blasting with adequate rock safety measures tunnel boring machines in soft and hard rocks with rock safety measures or segment lining 3

4 risk assessment in an early stage of the project what do we know advantages and limits of the construction method excavation tolerance bearable groundwater pressure on tunnel lining value of rock strength limiting mechanical excavation methods value of rock strength requiring additional rock safety measures improving methods to stabilize adoptable construction methods and rock safety measures in squeezing rock treatment of water bearing rock and unpredictability of karst structures in limestone 4

5 ) construction methods Access Shafts Moraine clay / silt / sand / (boulders) Molasse claystone / siltstone / Limestone / Urgonian / Prealps short shafts < 20 m only short shafts < 20 m with shaft in claystone only shaft in claystone with shaft in limestone shaft in limestone pile wall for mixed condition conventional (ripper, hammer) not relevant due to low permeability diaphragma wall shaft sinking machine (gripper) conventional (blasting) conventional (blasting) stiff clay with continuous underpinning medium long shafts < 40 m only pile wall for mixed conditions evtl. diaphragma wall diaphragma wall conventional (hammer, blasting) conventional (hammer, blasting) conventional (blasting) conventional (blasting) shaft sinking machine (gripper) <60 Mpa shaft sinking machine (gripper) <60 Mpa concrete structures in karstic zones concrete structures in karst zones long shafts < 80 m only medium long shafts < 40 m with long shafts < 80 m with shaft in siltstone/ shaft in molasse shaft in siltstone/ shaft in molasse shaft in limestone with passiv karsts backfilling voids for durability shaft in molasse shaft in limestone with aktiv karsts backfilling voids for durability bypass to allow natural water flows crossing filled karst structures shaft in molasse diaphragma wall diaphragma wall shaft sinking machine shaft sinking machine pregrouting to stabilize fault zone pregrouting to stabilize fault zone pregrouting to stabilize fault zone with pregrouting to stabilize fault zone very longt shafts > 80 m only diaphragma wall shaft sinking machine with larger pilot shaft very longt shafts > 80 m with diaphragma wall shaft sinking machine with larger pilot shaft 5

6 risks in Molasse Access Shafts Molasse claystone / siltstone / shaft in claystone only conventional (ripper, hammer) shaft sinking machine (gripper) shaft in siltstone/ conventional (hammer, blasting) shaft sinking machine (gripper) <60 Mpa shaft in molasse pregrouting to stabilize fault zone shaft in claystone with not relevant due to low permeability shaft in siltstone/ conventional (hammer, blasting) shaft sinking machine (gripper) <60 Mpa shaft in molasse pregrouting to stabilize fault zone risks risk reducing actions remaining risk no grip in claystone hard rock out of roadheader range place of shotcrete or liner plates ahead of grippers weakening of hard rock by loosening blasting low risk low risk 6

7 construction methods Experimental Halls Molasse claystone / siltstone / Limestone / Urgonian / Prealps cavern in claystone only cavern in claystone with cavern in limestone cavern in limestone conventional, ripper/hammer/roadheader not relevant due to low permeability forepoling with pipe or spile umbrella conventional, blasting conventional (blasting) split of heading face into smaller sections split of heading face into smaller sections split of heading face into smaller sections double vaults cavern in siltstone/ not relevant, below groundwater level evtl. conventional, blasting conventional, blasting conventional (blasting) conventional, roadheader (< 60 MPa) conventional, roadheader (< 60 MPa) concrete structures in karst zones split of heading face into smaller sections split of heading face into smaller sections backfilling voids for durability bypass to allow natural water flows crossing filled karst structures cavern in molasse cavern in siltstone/ cavern in molasse cavern in limestone with passiv karsts cavern in molasse cavern in limestone with aktiv karsts cavern in molasse pregrouting to stabilize fault zone pregrouting to stabilize fault zone pregrouting to stabilize fault zone pregrouting to stabilize fault zone 7

8 construction methods Experimental Tunnel Molasse claystone / siltstone / Limestone / Urgonian / Prealps tunnel in claystone only tunnel in claystone with conventional with roadheader not relevant due to low permeability shielded TBM with segmental lining conventional, blasting conventional, blasting gripper TBM with conventional lining shielded TBM with segmental lining shielded TBM with segmental lining gripper TBM with conventional lining gripper TBM with conventional lining tunnel in siltstone/ not relevant, below groundwater level evtl. conventional with roadheader (< 60 MPa) conventional with roadheader (< 60 MPa) conventional (blasting) conventional, blasting conventional, blasting shielded TBM with segmental lining shielded TBM with segmental lining shielded TBM with segmental lining gripper TBM with conventional lining gripper TBM with conventional lining gripper TBM with conventional lining concrete structures in karst zones backfilling voids for durability bypass to allow natural water flows crossing filled karst structures tunnel in molasse tunnel in siltstone/ tunnel in molasse with passiv karsts tunnel in molasse with aktiv karsts tunnel in molasse pregrouting to stabilize fault zone pregrouting to stabilize fault zone pregrouting to stabilize fault zone pregrouting to stabilize fault zone 8

9 Experimental Tunnel risks in Limestone / Urgonian / Prealps conventional, blasting conventional, blasting shielded TBM with segmental lining shielded TBM with segmental lining gripper TBM with conventional lining gripper TBM with conventional lining with passiv karsts not relevant, below groundwater level tunnel in molasse pregrouting to stabilize fault zone 9 Limestone / Urgonian / Prealps with aktiv karsts evtl. conventional (blasting) shielded TBM with segmental lining gripper TBM with conventional lining concrete structures in karst zones backfilling voids for durability bypass to allow natural water flows crossing filled karst structures tunnel in molasse pregrouting to stabilize fault zone risks risk reducing actions remaining risk use of concrete loss of injected material in low risk (except high structure and water karst structures construction costs) bypass TBM subsidence below vertical excavation axis due to karst in invert zone TBM subsidence below vertical excavation axis due to karst in invert zone relevant loads, extensions and possible abutments unknown unknown extension of karsts unknown variable water quantities mud intrusions under high pressure continuous exploration in invert zone ahead of tunnel face with bore holes continuous exploration in invert zone ahead of tunnel face with bore holes no risk reducing action possible until exploring karst structure to cross speleological exploration of the surrounding area prior to start and during construction long-time observation of local water balance and quantity increase during heavy rainfall continuous exploration ahead of tunnel face by seismic prediction methods and bore holes significant risk remaining significant risk remaining low risk (except high construction costs) low risk (except high construction costs) low risk (except high construction costs) significant risk remaining

10 risk assessment in an early stage of the project what is next create general geological longitudinal profiles for each relevant geological zone Moraine: e.g. groundwater level + boulders Molasse: e.g. clay stone Urgonian: e.g. karst all rocks: high water ingress hydrocarbon (gas) 10

11 risk assesment in an early stage of the project what is next define relevant geotechnical data of soil/rock for each relevant geological zone in connection with the local situation (e.g. overburden, building density,.) 11

12 risk assessment in an early stage of the project what is next verify applicability of above proposed construction methods based on the compiled geological/geotechnical data (e.g. in squeezing rock) assess best applicable construction method for each construction element (shafts/experimental halls/experimental tunnels) add necessary additional measurements and estimate the remaining risk search for exceptional measurements to allow excavation in case of remaining risk in special occasions or emergencies 12