Tunnel Exploration Drilling Rig Fault Zone: CSD1300L in Jinyang, Sichuan, China
Executive Summary
In Pailai Town, Jinyang County, Sichuan Province, Chengdu Chuanshan Drilling Engineering Co., Ltd. carried out adit (tunnel) exploration through a fully faulted formation — ground broken by faulting from surface to target depth. The contractor selected the CORTECH® CSD1300L crawler full hydraulic core drilling rig and completed a 952.20 m deep exploration hole at a 75 mm final diameter in 60 days. In a fault zone, broken and fractured rock tends to cause hole deviation, stuck tools and poor core recovery; the CSD1300L's precise hydraulic weight-on-bit control, 127 kN pullback and crawler stability kept the hole straight and the core recoverable, delivering the geological data needed ahead of tunnel construction.
Project Background & Challenge
Tunnel and adit exploration in a fault zone is among the most demanding coring environments:
- Fully faulted ground: the entire section is broken by faulting, so the drill meets fractured, unstable rock the whole way — not just a short fractured interlude.
- Deviation risk: in broken rock, the bit wanders along weak planes, and a deflected hole gives misleading geology ahead of the tunnel alignment.
- Sticking and loss of circulation: fractured zones cause tool sticking, borehole collapse and lost drilling fluid.
- Core quality for tunnel design: intact core is required to judge rock mass quality, groundwater and fault geometry before tunneling begins.
Our Solution
Chengdu Chuanshan selected the CORTECH® CSD1300L, a crawler-mounted full hydraulic surface core drilling rig built for high-precision coring in difficult ground. The features that solved the fault-zone brief:
- Precise hydraulic WOB control: 100% full hydraulic circuitry with stepless weight-on-bit control and 127 kN pullback / 50 kN feed kept the bit stable in fractured rock, reducing wandering and protecting core recovery.
- Stable crawler base: the heavy-duty track chassis (30° climb, 2 km/h) set up firmly on mountainous, uneven exploration pads, damping vibration that would otherwise push the hole off-line.
- High-speed wireline coring: the 120 m/min wireline winch with 1,000 m rope capacity minimized tripping time, important when long strings must be run and retrieved in broken ground.
- Right-sized deep-hole rating: reference coring depths of 1,300 m (B size), 1,000 m (N size), 700 m (H size) and 400 m (P size) covered the 952.20 m production hole with margin.
- Lightweight, mobile: at 8.5 tons (5,100 × 2,350 × 2,600 mm), the rig moved along Sichuan's mountain roads to the remote adit site.
Key Results
| Metric | Value |
|---|---|
| Location | Pailai Town, Jinyang County, Sichuan, China |
| Work type | Adit (tunnel) exploration |
| Ground condition | Fully faulted (fault zone) formation |
| Final hole diameter | 75 mm |
| Final hole depth | 952.20 m |
| Project duration | 60 days |
| Rig | CORTECH CSD1300L crawler core drill |
| Drilling process | Diamond wireline core drilling |
| Operating company | Chengdu Chuanshan Drilling Engineering Co., Ltd. |
| Core/hole performance | Stable, low-deviation hole and recoverable core through fault zone |
For the full technical specifications of the CORTECH® CSD1300L, see the CSD1300L product page.
Customer Value & ROI
- Reliable geology ahead of the tunnel: a straight, low-deviation 952.20 m hole through the fault zone gave the design team accurate rock-mass and fault data, reducing tunneling risk.
- Fewer stuck-string events: precise WOB control and a stable crawler base minimized deviation and sticking in broken ground, protecting the 60-day schedule.
- Core recovery that matters: wireline coring returned usable core through the faulted section, supporting ground classification for the adit.
- Site access: the 8.5-ton crawler rig reached the remote mountain adit site without special heavy logistics.
FAQ
What is tunnel / adit exploration drilling?
It is core drilling from or toward a tunnel/adit alignment to map rock quality, faults and groundwater before excavation. In the Jinyang, Sichuan project, the CSD1300L drilled a 952.20 m exploration hole through a fully faulted zone.
Why are fault zones difficult to drill?
Faulted rock is broken and fractured, which causes hole deviation along weak planes, tool sticking, borehole collapse and lost circulation. A rig with precise weight-on-bit control and a stable base is needed to keep the hole straight and recover core.
How do you prevent hole deviation in fractured ground?
Use stepless hydraulic weight-on-bit control to keep the bit cutting evenly, a stable crawler base to damp vibration, and appropriate string stiffness. The CSD1300L's 127 kN pullback / 50 kN feed and full hydraulic loop delivered a low-deviation hole through the Sichuan fault zone.
How long did the 952 m Sichuan fault-zone hole take?
The CSD1300L completed the 952.20 m adit-exploration hole at 75 mm diameter in 60 days, working through a fully faulted formation for Chengdu Chuanshan Drilling Engineering Co., Ltd.