Foundation Drilling Case

Site Welding Solution for a
1500mm Roller Bit Core Barrel

Drillnova supported a first cooperation project on the G59 Highway with a site welding and cutter positioning plan for a 1500mm roller bit core barrel working in 100MPa+ fresh granite.

Location

Hunan

Rig

SANY 405R

Tool

1500mm Core Barrel

Formation

100MPa+ Granite

Contractor

Hunan Road & Bridge

Project Background

Hard granite required more than a simple roller bit replacement.

The site required 1200mm bored pile drilling through upper soil and weathered formations into harder rock. Before the rebuild, the site had experienced cutter seizure, dropped rollers, uneven wear, mud packing, and vibration during drilling.

Drillnova reviewed the original core barrel, cutter position, formation condition, drilling parameters, and on-site repair constraints before proposing the rebuild and operating suggestions

Field Diagnosis

Old cutter damage pointed to several possible causes

The site evaluation did not treat broken teeth as a single product failure. Drillnova reviewed formation matching,

operating parameters, fractured layers, isolated boulders, and the old core barrel geometry.

1 Severe hard rock load

100MPa+ granite increases impact load on roller cones, bearings, welds, and the barrel body.

2 Broken roller bit

The old barrel had three broken roller bits, possibly related to half-face rock, isolated boulders, or sudden impact.

3 Barrel ovality risk

The lower ring required center positioning to control cutter layout despite possible barrel deformation.

Drillnova Solution

A practical site welding plan for accurate cutter positioning

The old roller bit core barrel exposure and embedded depth were recorded as 80mm, 150mm, and 205mm. Drillnova recommended reducing the embedded depth to a standard 130mm by using spacer blocks cut from guide strips.

Field Results

Key data used for the repair plan

These values come from the field communication record and are used as project-specific reference points.

1500mm

Roller bit core barrel used for the 1800mm pile work

1.8m

Recorded core barrel length during field measurement

130mm

Recommended standard embedded depth after spacer adjustment

100MPa+

Fresh granite UCS in the project formation

Project Gallery

Selected images from the field log

The gallery shows the highway work area, rock samples, old roller bit barrel condition, and key measurement steps for the welding plan.

Engineering Learnings

What this case shows
about field repair support

For large roller bit core barrels, field welding accuracy directly affects cutter load, cutting path, discharge efficiency, and later wear pattern. A replacement plan should define both the cutter position and the welding process.

Measure before cutting

Existing exposure height, embedded depth, and cut size determine whether the new bit can work correctly.

Correct for barrel ovality

Center positioning helps avoid uneven cutter loading when the lower ring is not perfectly round.

Improve spoil discharge

Larger cut openings and scraper blocks can reduce packing around roller bits in hard rock drilling.

Match repair to geology

100MPa+ granite requires a conservative welding plan and careful operator awareness of impact conditions.

Related Tools

Tools and support for similar projects

Roller Bit

Heavy-duty roller bit for core barrels drilling tools working in hard formations.

Roller Bit Core Barrel

Custom core barrel design and repair support for hard rock bored pile drilling.

Double Wall Casing

Custom casing design for bored pile drilling project.

Project Support

Need a field repair plan
for a roller bit core barrel?

Send us your pile diameter, drilling depth, rig model, ground condition, and current tool photos.

Drillnova can recommend roller bit type, cutter layout, barrel structure, and operating suggestions for your jobsite.

Pilot Bit

Reamer

Soil Reamer

Accessories

foundation case hunan