In modern geotechnical engineering, self-drilling hollow anchor bolts have emerged as a game-changing solution for stabilizing unstable slopes, reinforcing tunnel walls, and securing foundations in challenging terrains. Sinorock, a pioneer in advanced rock anchoring systems, has perfected this technology to deliver unmatched efficiency, reliability, and adaptability. This article provides an in-depth exploration of the construction workflow for Sinorock’s self-drilling hollow anchor bolts, highlighting their unique advantages and addressing common client questions about implementation.
Why Choose Sinorock’s Self-Drilling Hollow Anchor Bolts?
Before diving into the construction process, it’s critical to understand why Sinorock’s systems outperform conventional methods:
- Integrated Design: Combines drilling, grouting, and anchoring into a single operation, reducing project timelines by up to 40%.
- Geological Versatility: Engineered for fractured rock, water-rich strata, and collapsible soils where traditional anchors fail.
- Corrosion Resistance: Proprietary anti-corrosion coatings extend service life to 50+ years, even in acidic or saline environments.
- Load Capacity: R32 and R38 hollow bars (yield strength ≥550 MPa) support axial loads up to 350 kN, ideal for heavy infrastructure.
- Cost Efficiency: Eliminates separate casing installation and reduces labor/machine downtime.=
Step-by-Step Construction Process
1. Pre-Construction Preparation
Laying the Foundation for Success
A. Site Assessment & Design Finalization
- Conduct geotechnical surveys to identify soil/rock composition, groundwater levels, and load requirements.
- Sinorock’s engineering team tailors anchor spacing (typically 1.5–3m), drilling angles (10°–30°), and embedment depth (6–25m) based on FEM analysis.
B. Material Inspection & Logistics
- Verify Sinorock-supplied components:
- Hollow anchor bars: Check for straightness, thread integrity (R-type or T-type), and internal grout channels.
- Drill bits: Select carbide-tipped (for hard rock) or diamond-coated bits (abrasive strata) from Sinorock’s catalog.
- Coupling sleeves: Ensure ISO-certified threading matches anchor bars.
- Grout mix: Use Sinorock’s pre-bagged cement (PO 42.5) or custom blends for aggressive environments.
C. Equipment Setup
- Deploy Sinorock-recommended rigs (e.g., hydraulic rotary drills with 20–30 kNm torque) equipped with:
- Rotary swivel adapters for simultaneous drilling/grouting.
- Digital inclinometers for angle precision (±1°).
- Automated grout pumps (pressure range: 0.5–3 MPa).
2. Drilling & Primary Grouting
Simultaneous Penetration and Stabilization
A. Anchor Bar Assembly
- Attach the drill bit to the hollow anchor bar using Sinorock’s double-start threads, ensuring a dust-proof connection.
- Mount the assembly onto the drill rig’s chuck, aligning it with marked drilling points.
B. Grout Mix Preparation
- Prepare primary grout using Sinorock’s optimized formula:
- Water-cement ratio: 1:1 (by weight)
- Additives: Non-shrink agents (0.5% by cement weight) to prevent cracking.
- Mix for 3–5 minutes until achieving a homogeneous, slump-rated (10–12 cm) consistency.
C. Simultaneous Drilling & Grouting
- Start drilling at 50–80 RPM while injecting grout through the hollow bar’s core at 10–15 L/min.
- Monitor real-time parameters:
- Grout return: Expect 70–80% outflow; absence indicates blockage.
- Drilling torque: Sudden spikes signal obstructions – retract/advance the bar to clear debris.
- Advance rate: Maintain 0.5–1.5 m/min in soft rock; adjust RPM for harder formations.
3. Secondary Pressure Grouting
Enhancing Bond Strength & Durability
A. Post-Drilling Grout Injection
- After reaching target depth, disconnect the grout line and install a packer at the collar.
- Prepare secondary grout with:
- Water-cement ratio: 0.45–0.6:1
- Micro-silica: 5–8% by cement weight to reduce permeability.
- Apply pressure gradually:
- Stage 1: 0.5 MPa for 2 minutes to fill voids.
- Stage 2: Increase to 1.5–2 MPa for 5 minutes, forcing grout into micro-fissures.
B. Curing Protocol
- Maintain ambient temperature >5°C; use thermal blankets if necessary.
- Allow 72 hours for compressive strength to reach 25 MPa (per Sinorock’s accelerated curing tests).
4. Anchor Bar Extension (If Required)
Seamless Integration for Deep Anchoring
For depths exceeding single-bar limits (standard lengths: 3m/6m/9m):
- Retract the drill slightly to expose threads.
- Apply Sinorock’s thread sealant to coupling sleeves.
- Connect the new bar using a hydraulic torque wrench (250–300 Nm).
- Resume drilling while monitoring alignment via laser guidance systems.
5. Installation of Bearing Plates & Nuts
Locking the System in Place
A. Surface Preparation
- Cut the exposed bar to 150–200mm above the face.
- Clean debris and apply anti-corrosion paste to threads.
B. Component Assembly
- Slide Sinorock’s dome-shaped bearing plate (200×200×20mm, Q235 steel) onto the bar.
- Tighten the hex nut (Grade 8.8) to 70% of yield strength using calibrated torque wrenches.
- After 7 days, perform final torqueing to compensate for grout shrinkage.
Conclusion: Building Confidence with Sinorock’s Expertise
The self-drilling hollow anchor bolt process represents a leap forward in geotechnical engineering, and Sinorock stands at the forefront of this innovation. By integrating precision manufacturing, rigorous R&D, and hands-on field experience, we deliver solutions that tackle the most complex stabilization challenges while keeping projects on time and under budget.
From the slopes of hydropower dams to the depths of urban metro tunnels, Sinorock’s systems have proven their reliability in 60+ countries. Let our team guide you in selecting the optimal anchor configuration for your next project. Contact us today for a free geological assessment and system design proposal.
