Pipe Proofing & Ring Bit Combined (Concentric Pipe Roofing System) Pipe Proofing
INTEGRATED PIPE ROOFING & CONCENTRIC RING BIT SYSTEM

Pipe Proofing & Ring Bit Combined (Concentric Pipe Roofing System)

The Integrated Pipe Proofing and Ring Bit System is an advanced geotechnical pre-support solution combining high-strength S355 structural steel casing pipes with precision-engineered Symmetrix concentric ring bit sets. By uniting the load-bearing umbrella arch casing with an integrated sacrificial ring bit and central pilot bit, the system advances heavy steel casings simultaneously through unpredictable boulders, gravel, fault zones, and fractured strata with zero ground loss, maximum borehole straightness, and 100% pilot bit retrieval.

Integrated Pre-Support Canopy
Creates a continuous protective structural umbrella arch ahead of the tunnel excavation face.
Concentric Single-Pass Drilling
Advances heavy casing pipe simultaneously with the concentric ring bit cutting face in loose or boulder-filled ground.
100% Pilot Bit Retrieval
Central pilot bit is unlocked and fully retrieved through the casing once target borehole depth is reached.
High-Strength S355 Alloy Steel
Premium S355 grade casing delivering up to 630 N/mm² tensile strength for maximum overburden load transfer.
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ENGINEERING METRICS

TECHNICAL DATA & SPECIFICATIONS

Certified engineering tolerances, metallurgical grades, and load metrics for heavy geotechnical installations.

Pipe Proofing & Ring Bit Combined (Concentric Pipe Roofing System) — Technical Data Sheet

Quality Assurance Standard: ISO 10208 / EN 14199

# Technical Metric Certified Specification
01
System Architecture
Integrated S355 Pipe Roofing Casing + Symmetrix Concentric Ring Bit Shoe
02
Casing Steel Grade
S355 Structural Alloy Steel (EN 10025 / DIN 17100 St 52-3)
03
Casing Pipe Diameters (OD)
76.1 mm, 88.9 mm, 114.3 mm, 139.7 mm, 168.3 mm
04
Matching Ring Bit Diameters (OD)
89.0 mm, 102.0 mm, 127.0 mm, 152.0 mm, 185.0 mm
05
Matching Pilot Bit Diameters (OD)
74.0 mm, 86.0 mm, 110.0 mm, 135.0 mm, 165.0 mm
06
Compatible DTH Hammer Sizes
DTH 2.5", DTH 3", DTH 3.5", DTH 4", DTH 5", DTH 6"
07
Minimum Yield Strength
355 N/mm² (Casing Pipe) | Direct impact transfer shoulder
08
Tensile Strength Range
490 – 630 N/mm² (EN 10025 S355 Standard)
09
Tungsten Carbide Hardness
87–89 HRA (Carbide Inserts) | 50–55 HRC (Bit Body)
10
Starter Pipe Assembly
Sacrificial ring bit factory-welded to first pipe; follower pipes threaded/welded
11
Flushing System
Multi-port central and peripheral water/air flush channels for fast cuttings discharge
12
Primary Applications
Tunnel Portals, Crown Umbrella Arches, Collapsible Forepoling, Deep Foundation Shoring
100% Ultrasonic flaw tested and batch certified under ISO 9001:2015 QA procedures.
Request Mill Test Certificate (MTC)
 
Verified Technical Reference

Concentric Pipe Roofing Umbrella & Ring Bit System Overview

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The concentric overburden drilling system integrates high-yield structural casing pipes with a heavy-duty Symmetrix ring bit shoe and central pilot bit. The pilot bit transfers impact energy directly to the ring bit shoulder, drilling the full borehole void while simultaneously pulling the casing pipe forward without excessive torque. Once borehole depth is achieved, reverse rotation unlocks the pilot bit for complete retrieval, leaving the casing and ring bit in place for immediate high-pressure grouting.

Symmetrix Concentric Ring Bit & Pipe Roofing Casing Sizing Matrix

Casing Pipe OD Casing Pipe ID Ring Bit OD Ring Bit ID Pilot Bit OD DTH Hammer Size
76.1 mm (3.0") 66.0 mm 89.0 mm 65.0 mm 74.0 mm DTH 2.5" / 3"
88.9 mm (3.5") 78.0 mm 102.0 mm 77.0 mm 86.0 mm DTH 3" / 3.5"
114.3 mm (4.5") 101.0 mm 127.0 mm 100.0 mm 110.0 mm DTH 3.5" / 4"
139.7 mm (5.5") 125.0 mm 152.0 mm 124.0 mm 135.0 mm DTH 4" / 5"
168.3 mm (6.6") 150.0 mm 185.0 mm 149.0 mm 165.0 mm DTH 5" / 6"

Casing Pipe Steel Grade Mechanical & Chemical Properties

Standard Equivalent Yield Strength (Min) Tensile Strength Elongation (Min) Carbon (C) Max Manganese (Mn)
EN 10025 S355 DIN 17100 St 52-3 355 N/mm² 490 – 630 N/mm² 22% 0.20% 1.60% Max
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