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GROUND TREATMENT WORKS COMPENSATION GROUTING FARRINGDON STATION Client: CrossRail Main Contractor: BFK (Bam-Ferrovial-Kier JV) Site Location: Farringdon.

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Presentation on theme: "GROUND TREATMENT WORKS COMPENSATION GROUTING FARRINGDON STATION Client: CrossRail Main Contractor: BFK (Bam-Ferrovial-Kier JV) Site Location: Farringdon."— Presentation transcript:

1 GROUND TREATMENT WORKS COMPENSATION GROUTING FARRINGDON STATION Client: CrossRail Main Contractor: BFK (Bam-Ferrovial-Kier JV) Site Location: Farringdon - Barbican Subcontract Value: £11.1m The construction of the new Farringdon Station within the C435 Crossrail contract requires ground treatment works to secure a safe ground behaviour and protect the nearby assets and structures. These works are being carried out by Geocisa UK and they mainly consist of compensation grouting, For that purpose, five grouting shafts were installed in the new station area and along the new tunnel route. The injection of cement grout through tube- à-manchette (TAM) pipes installed in the ground is being performed to compensate the movements produced by the excavation of the main two tunnels using Tunnel Boring Machines (TBMs) and also during the enlargement of those tunnels between the West Ticket Hall (Farringdon) and the East Ticket Hall (Barbican) and the excavation of the different station galleries and the aforementioned ticket halls. This location, at the heart of the City of London, it is a very congested and built up area with in-use London Underground and National Rail tracks, important heritage buildings, very sensitive structures, sewers and all kinds of services. GEOLOGY The ground in this area consists of 6-10m of Made Ground and 4-7m of London Clay. Beneath those two layers, Lambeth Group Formation is encountered. During the drilling phase, all the TAMs were installed in the London Clay layer, except for the ones installed in Buther’s Ramp Shaft, that were installed in the Lambeth Group with occasional but important presence of water. 6 Mitre Passage, Floor 8 - Greenwich Peninsula - London, SE10 0ER INFO: Figure 1: longitudinal Section & geology

2 GROUND TREATMENT WORKS PHASE 1: DRILLING Horizontal drill holes were laid-out covering the influence zone of all the tunnels and cross passages. A total of 357No. boreholes were drilled and inside each of them steel TAM pipes with valves every 0.5m were installed. The drill holes were installed in the London Clay and Lambeth Group with lengths varying from 5m up to 84m long. PHASE 2: GROUTING OPERATIONS PRE-TREATMENT. This is the phase when the grouting is carried out prior to the commencement of settlement as a result of excavation, so as to verify that the grouting system is active and that controlled movement of the protected assets can be produced. This phase was completed before the TBMs arrival according to the contractual requirements, allowing a safe and controlled TBM passing through the Farringdon Station work site. COMPENSATION GROUTING. This grouting is carried out simultaneously with settlement inducing construction activities to mitigate ground movements as they are generated. This operation requires a continuous coordination and feedback with the SCL tunnel team. With highly challenging and demanding criteria, the grouting works are successfully complying with the KC21 specification from CRL. JACKING. This phase is defined as episodes of grouting designed specifically to produced controlled uplift which are either: PRE-JACKING: grouting performed in an area prior to any construction activity that may induce settlements. POST-JACKING: grouting performed after settlement inducing construction activities, but which are not directly related to any current excavation. These grouting works are developed in close coordination between the Grouting and Instrumentation & Monitoring (I&M) teams to control the ground movements. All these stages are summarized in the previous figures and in the table below: 6 Mitre Passage, Floor 8 - Greenwich Peninsula - London, SE10 0ER INFO: – Figure 2: Longitudinal SectionFigure 3: BR Shaft - Concurrent Grouting Vertical Movements CHSMS1MS2MS3BR TOTAL No. drillholes TOTAL length drilled (m) 2,6213,9854,4322,3624,68618,086 Average borehole length (m) Pre-Treatment (Y/N)  Pre-Jacking (Y/N)    Post-Jacking (Y/N)   Compensation Grouting (Y/N)  TOTAL Vol. grouting (m 3 )


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