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Tunnel optimisation for future colliders at CERN

Alexandra Tudora John Osborne

SITG Forum

27.11.2019

SMB Agenda

• Introduction

• CERN infrastructure and proposals for future colliders

• Tunnel Optimisation Tool

– Requirements

– Data interpretation and input

– How TOT works

• Civil Engineering overview for FCC and pre-construction planning

• Current status of FCC study and going forward

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Future Accelerator Studies Section (FAS)

Section Leader: John OSBORNE

Engineers

International Linear Collider CLIC, Muon Collider

Jonathan Gall

Tunnel Asset Management

Alexandra Tudora

Future Circular Collider (FCC)

Physics Beyond Colliders (PBC)

SMB-SE-FAS Section Organisation

Ben Swatton

Tunnel Fibre Optic Studies

Zhipeng Xiao

Selected CE Project Delivery

Eliseo Perez-Duenas

SMB CERN – The World’s Largest Particle Physics Laboratory

CERN – European Centre for Nuclear Research

SMB Existing tunnels at CERN

Large Hadron Collider :

- 27km circumference

- 50-175m depth

Total underground tunnels >70km More than 80 Caverns

LEP tunnel built in mid 1980’s

SMB Underground works in progress at HL-LHC

SMB Proposed Future Colliders at CERN

‘’The European Strategy for Particle Physics provides a clear prioritisation of European ambitions in advancing the particle physics science. The Strategy is due to be updated by May 2020 to guide the direction of the field to the mid-2020s and beyond.’’ https://europeanstrategyupdate.web.cern.ch/welcome

SMB The Future Circular Collider

Collision energy: 100TeV

Circumference: 80km-100km

Physics considerations: Enable connection to the LHC (or SPS)

Construction: c.2025-35

Cost: ˜6Billion CHF for Civil works

Aims of the civil engineering feasibility study: Is 80km-100km feasible in the Geneva basin? Can we go bigger? What is the ‘optimal’ size? What is the optimal position?

Spoil: ˜10million m3 of excavated material

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Option 2: 80km Lakeside Option 1: 80km Jura

Potential locations - European Strategy 2012

High

Low Feasibility

Risk

water ingress

heaving ground

weak marls

hydro carbons

support & lining

ground response &

convergence

hydrostatic pressure & drainage

Pollution of

aquifers

effect of shafts on

nature

effects of shafts on

urban areas

Tota

l

Jura 80 5 3 0 0 5 4 5 5 4 2 33

Lake 80 2 0 3 3 3 3 2 2 3 2 23

Lake 47 1 0 2 2 2 2 1 1 2 5 18

Pre-feasibility study focused on: • geology & hydrogeology, • tunneling & construction, • environmental impacts

Result: for the 80km long tunnel location 2 ‘80km Lakeside’ is most feasible.

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The Study Boundary was defined by: • Topography (avoid Jura, Vuache, Pre-Alps) • Geology (maximise tunnelling in molasse) • Geneva Lake (lake depth increases in NE direction) • Connection to LHC

FCC Study Boundary

Multiple shapes and sizes studied within the boundary

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Bespoke tool

• Common Data Environment

o Single Source of Data and ‘Truth’

• Open Source Development

o Accessible user-friendly interface

• Integrated visual decision aid

platform

Tunnel Optimisation Tool

SMB Requirements and development of TOT

Physics requirements: o Machine shape

(lengths of straights sections and arcs);

o Location of experimental points and injection from the LHC;

Geology: o Surface and subsurface mapping o Integration within 3D Geological Model

Civil Engineering: o Intersected geology o Depths of shafts o Overburden pressure o Surface sites (environmental constraints, access etc)

Opt

ione

erin

g It

erat

ion

Cos

ting

and

Ris

ks A

naly

sis

SMB 3D geological model

The DEM has been sourced from the EU Copernicus programme and has a quoted vertical accuracy of +/- 2.9m

Digital Elevation Model (DEM)

SMB Data interpretation and input into TOT

Molasse rockhead contours

This data was then processed by Geneva Geo Energy to create a Limestone rockhead depth map covering the FCC study area. GGE cautioned that due to interpolotion over large distances, local inaccuracies of up to +-50m are possible

(Geneva Geo Energy, 2014)

Limestone rockhead contours

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Prealps

Voirons - Faucigny

Jura

Vuache Mandallaz

Regions with high uncertainty and challenging geology

Geological interpretation

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• Geology underneath Lake Geneva is not yet well understood

• Data available from boreholes and seismic scans

• Molasse bedrock covered by a deep layer of moraines

140m shaft depth

Lake Geneva Bathymetry

Data interpretation and input into TOT

71m 58m 60m

87m

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• Natural parks • Areas of biological significance

and wetlands • Protected water sources • Groundwater (aquifers)

Environmentally sensitive areas

Data input into TOT

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Buildings

• Buildings data covers both the Swiss and French sides of the FCC study area.

• In Switzerland, the data includes buildings with planning permission

Data input into TOT

SMB SITG data

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Geothermal boreholes

• Over 1800 boreholes in the FCC study area ranging from 20m – 400m in depth.

• Only 10 to 20 boreholes are usually within a 50m radius of a given FCC tunnel option under study

Input data into TOT

SMB FCC TOT demo

SMB FCC Conceptual baseline footprint

Present baseline position was established considering: • lowest risk for construction

Avoid Jura limestone and the Pre-Alps Only one sector containing limestone. ~90 % molasse – suitable

ground for tunneling Significantly reduced total shaft length. Deepest shaft at PF

proposed to be replaced with an inclined tunnel Avoids extremely large overburden.

• feasible positions for large span caverns (most challenging structures) • experimental Site at Point A on existing CERN land.

97.75km tunnel circumference

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24 Underground civil infrastructure for FCC - 3D schematic (not to scale)

Shafts: Experimental Shafts: 15 m dia. + 10 m dia. Service shafts: 12 m dia. Magnet delivery shaft:18 m

Service Caverns • 25 m x 15 m x 100 m

Small Experimental Caverns 30 m x 35 m x 66

Large Experimental Caverns 35 m x 35 m x 66 m

Beam Dump Caverns • 10 m x 10 m x 50 m

Alcoves • 25 m x 6 m x 6 m • Located at 1.5km spacing

Tunnels: • 97.75 km of 5.5 dia. machine tunnel • Approx. 8 km 5.5 dia by-pass tunnels

FCC Civil engineering overview

SMB FCC pre-construction planning

European Strategy Update 2020

Types of site investigation: • Collection of existing information • Walkover survey • Geophysical investigations (to define interfaces) • Boreholes

• Site testing (eg Insitu stress test, point load testing, SPT) • Rock laboratory testing.

Phases: Feasibility: Non-intrusive investigations to allow consolidation of alignment. Focus on access points, Lake crossing and the Rhone and Arve crossings. Principal: Substantial portion of the geotechnical investigations. As a result of this, the alignment might need to be changed. Additional: Any investigations required for the final design, emphasis on obtaining date required for the contractors.

Conceptual Design Report

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• Information near to CERN is strong due to previous experience on LEP/LHC.

• Multiple deep boreholes in the area.

Vallée de l‘Arve Mandallaz

Le Rhône Lake Geneva

• No deep borehole information available in the area.

• Complex faulted region. • Molasse/limestone interface uncertain.

• Moraine/molasse interface not certain, cavern close to interface.

• Lack of deep boreholes in area.

• Seismic and borehole information for lake crossing from proposed road tunnel, but layered nature of lake bed leads to uncertainty.

• Location of the interface between molasse and molasse subalpine not certain, tunnel alignment in proximity.

• Limestone formation known, but characteristics and locations of karsts unknown.

• Alignment close to limestone rockhead.

• The exact location and angle of the limestone/molasse interface undefined.

Geological uncertainty

SMB Going forward

Currently focusing on

• continuous desktop study of geology

• planning for preparatory works to start the site investigations campaign

• optimising the footprint

CERN Tunnelling Workshop (23-24 October 2019) - Review software and decision aid tools available and what the industry are using for alignment optimisation → https://indico.cern.ch/event/823271/

Exploring GIS tools and alignment optimisation software that could facilitate future colliders studies from

feasibility stage throughout detailed design stage up to construction start

Awaiting news from European

Strategy for Particle Physics Update May 2020

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Thank you for your attention!

Any questions?

Contact: Alexandra.tudora@cern.ch