Xi'an Heaven Abundant Mining Equipment CO.,LTD
Fractured rock is one of the most demanding conditions a drilling crew can face. Cracks, joints, and voids weaken the rock mass, absorb impact energy, and make it easy for the hole to drift off line or for the bit to jam. Yet fractured ground is common in mining, water well, and construction projects, so learning how to pick the right DTH drilling tool for these conditions is a practical skill every driller should have. This guide explains what happens underground when you drill through broken ground, and how to choose equipment that keeps penetration steady and tool life long.
A solid, homogeneous rock transmits the hammer's impact energy straight into the bottom of the hole, breaking the rock in a predictable pattern. Fractured rock does not behave that way. The cracks and open joints scatter the impact energy, so part of every blow is lost before it reaches solid material. The result is slower penetration, more vibration, and a higher chance that the bit wanders off course.
There is also the risk of spalling. When the bit strikes a block that is only loosely held by surrounding rock, the block can break away unevenly, leaving an irregular hole wall. In severe cases, loose material falls into the hole and gets trapped between the bit and the borehole wall, which is the classic cause of bit jamming and stuck strings. Water inflow makes things worse, because it carries fine particles into the cracks and can wash away the cuttings the bit is trying to flush out.
Because of all this, a bit that performs beautifully in solid granite can disappoint badly in the same granite once it is heavily jointed. The tool selection has to change with the ground, not just with the rock type.
The face design is the first thing to get right. For broken and fractured formations, a convex or ｄｒｏｐ-center face is usually the safer choice. The center of the bit contacts the rock first, and the engagement zone spreads outward as the blow lands. This progressive contact spreads the lateral forces across more buttons, which reduces the shock on any single ｉｎｓｅｒｔ and helps stop the bit from being pushed sideways when it meets an uneven block. It also gives better hole guidance, which matters a lot when the ground around the hole is not stable enough to hold the bit in line by itself.
Button layout is the second factor. In fractured rock, the buttons need to be spaced so that the bit can still crush rock between cracks without letting the buttons dig into a single block and get snapped off. Wide-body button bits with a well-distributed button pattern handle irregular rock much better than aggressive, tightly packed layouts. Tungsten carbide grade matters too; a tougher grade that absorbs shock without chipping will outlast a harder but more brittle grade in broken ground.
Cuttings removal is the third factor, and it is easy to overlook. In fractured rock, the hole wall is not a clean cylinder, so cuttings have more places to get stuck. A bit with generous flushing holes and a design that keeps air moving up the annulus will clear the hole faster and reduce the chance of re-drilling your own cuttings. This becomes even more important when groundwater is present.
No single bit works everywhere, and the same is true within fractured rock itself. The right choice depends on how broken the ground is and how hard the intact blocks are.
If the project crosses several rock types in one hole, which is common in water well drilling, a versatile face design that performs acceptably across the range is usually better than a bit that is perfect for one formation and poor in the others.
Operating air pressure has a direct effect on how a DTH tool behaves in fractured ground. Low-pressure DTH drilling is often preferred for smaller holes and for projects where the budget for compressor capacity is limited. In broken rock, the gentler blow can actually be an advantage, because it reduces the shock transmitted to the surrounding rock and lowers the risk of spalling and hole collapse.
High-pressure drilling delivers much more impact energy and is the standard choice for hard rock mining, large-diameter blast holes, and deep water wells. In fractured ground, the extra energy helps the bit break through the intact blocks between cracks, but it also demands a bit that can take the punishment. The key is to match the pressure to the hammer and bit rating, and to make sure the compressor can deliver the airflow the hammer needs. An undersized compressor is one of the most common causes of slow drilling and stuck bits, and it is a problem that no amount of bit selection can fix.
A DTH bit works as part of a system. The hammer generates the blow, the bit delivers it, and the drill rods carry rotation and air down the hole. In fractured rock, the rods matter more than people expect. A heavy, stiff rod string keeps the bit loaded against the bottom and resists the sideways forces that cause deviation in broken ground. Light or worn rods flex under load, and that flex turns into a wandering hole.
For the same reason, the connection between the hammer and the bit should be checked before every shift. A loose or worn thread lets the bit wobble, and in fractured rock a wobbling bit will quickly round off the hole and hammer its own gauge buttons to pieces.
Xi'an Heaven Abundant Mining Equipment Co., Ltd. (TY Drill Bits), founded in 2010 in Xi'an, Shaanxi, China, has built its business around exactly this kind of practical drilling problem. The company is an ISO9001-certified manufacturer and exporter that supplies a complete range of rock drilling tools, including DTH hammers, DTH bits, drill rods, and thread button bits, all under one roof. Because the team handles development, production, and sales together, they can match a tool to a specific geological condition rather than pushing a one-size-fits-all product.
For fractured and broken formations, the DTH range includes low-air-pressure bits such as the Cir70-76mm and Cir110-110mm models, which suit softer, more disturbed ground, and high-air-pressure bits like the 6-inch mining DTH drill bit for harder broken rock. The DHD3.5-90mm and BR2-75mm hammer bits cover mining and borehole work, while the QL50-152mm bit handles larger-diameter bore holes. When the ground is too unstable for a conventional bit, the range of thread button bits and retrac designs gives crews an alternative for keeping the hole open and on line.
The supporting equipment is part of the same story. DTH drill rods with API 2 3/8 Reg connections, in standard 3-meter lengths, are available to complete the string, and the factory can produce custom sizes on request. With OEM services offered and a typical lead time of around 15 working days, TY Drill Bits is set up to supply both standard stock items and project-specific tooling.
Fractured rock will never drill as cleanly as solid ground, but the right DTH drilling tool makes the difference between a slow, frustrating hole and a steady, economical one. Choose a face design that keeps the bit stable, a button layout and carbide grade that survive the shocks of broken ground, and a flushing system that clears the hole. Match the air pressure to the formation, and do not forget the rods and connections that carry the whole system. With the right combination, fractured rock stops being a problem and becomes just another formation to drill.
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