Why a Screw Pile Won't Drive - The Roots of the Problem

When a pile won't drive properly, the root cause is almost always the soil. But it's important to understand that not every difficult section is created equal. Sometimes a pile gets stuck in a clay lens, while other times it literally hits a boulder. To figure this out, you need to understand what exactly is preventing it from driving.

Here are the main types of problematic soils:

·         Stony or bouldery soil. Underground, there may be a block, a boulder, or simply a scattering of large crushed stone. A pile won't cut into such material—it either hits the ground or goes sideways.

·         Gravel with clay. This type of soil can "chew" the pile: at first, it goes forward, then suddenly slows down. It seems like it's stuck, but in reality, there's simply not enough torque.

·         Rocky soil. In this case, a screw pile physically can't drive. It's like drilling granite with a screwdriver—futile. How do you know if a pile isn't going?

·         The machine is turning, but the pile remains in place.

·         It's going, but there's a pull—off-center.

·         You feel a sharp impact or a sudden stop.

This is usually noticeable within the first three turns. If you have an experienced contractor, they'll immediately realize that the problem isn't the piles or the driller—it's just the soil.

What to do if a pile is stuck: on-site options

If a pile isn't moving, don't panic. In 90% of cases, the situation can be resolved right on-site, without disrupting the schedule or redoing the entire foundation. The key is to avoid forcing it, as this can strip the threads, damage the shaft, or push the pile to the side.

Here's what usually helps:

·         Reinstalling the pile half a meter from its current location. The easiest way is to try screwing the pile in next to it. Rocks and boulders rarely form a wall; they can be avoided. The key is not to move too far to avoid disrupting the foundation's geometry.

·         Preliminary excavation (manual exploration of the hole). If the area is clearly rocky, you can try digging a pit up to 50–70 cm deep and inspecting the area. Sometimes a single boulder is encountered; remove it and screw it in.

·         Replacing a screw pile with a bored pile. When the ground is completely blocked, we install a drill, make a hole, and reinforce it with a concrete support. This option is more expensive, but it helps where a screw pile physically won't work.

·         Use a smaller diameter pile.

 

When Screw Piles Won't Work

Sometimes, no matter how you look at it, you have to admit: screw piles aren't an option. This doesn't happen often, but it's better to know upfront than to waste time, money, and stress. Below are typical cases where the project should be reconsidered.

Rocky Soil

If the underlying soil is limestone, granite, or other hard rock, a screw pile won't fit at all. Not because the installer is bad, but because metal against rock is a surefire loser.

Fill Soil with Large Construction Debris

Sometimes, the site is filled haphazardly—brick, concrete, rebar. In this case, the pile will constantly bump into unpredictable obstacles. It's easier to install bored piles or a slab foundation.

Shallow Rock Mass

If the geology shows that the rock layer begins at a depth of 50–70 cm, it's better to immediately install an alternative. In such cases, either concrete drilling or micropiles are used.

The soil isn't always to blame: common installation mistakes

Sometimes a pile won't go in not because there's a rock or boulder there, but because the installation was done poorly. This happens more often than you'd like, especially when working with inexperienced installers or "cheap crews."

Here are the main mistakes that can stop a pile:

·         Incorrect entry angle. If the pile isn't aligned vertically from the start, it will hit the side of the hard ground or drift sideways. The deeper it goes, the more distorted it becomes.

·         Insufficient torque. Sometimes, a weak gearbox is installed, there's no hydraulics, or the pile is driven manually. Such a pile simply won't go into hard ground—it gets stuck and spins in place.

·         Poorly sharpened blade. If the blade is dull or deformed, it doesn't cut the soil but tries to push it through. This is especially critical in clayey and dense areas. • Seasonality wasn't taken into account. In spring and fall, the soil may be half-soaked or have frozen lenses.

How to avoid this:

·         Ensure installation is mechanized and with the required force.

·         Ensure the pile is installed strictly level.

·         Before starting, ask for a test drive on 1-2 piles.

Proven Solutions: What Works in Practice

When a pile won't go anywhere, the key is not to bang your head against the concrete, but to assess the situation soberly. The approach shouldn't be one-size-fits-all, but tailored to the specific situation. Here are four effective methods that are actually used on construction sites.

Pile Offset

If the site allows, we shift the pile 30-50 cm laterally. Simply going around the boulder or clay layer often helps. The main thing is to pay attention to the overall foundation geometry, especially under walls and load-bearing elements.

Preliminary Drilling

Using a garden auger or a motorized auger, we drill a hole 70-100 cm deep. This makes it easier to penetrate the upper dense layers and aim accurately. Then we drive the pile into this hole. This method often works in clay and crushed rock soil.

Installing a Bored Pile Instead of a Screw Pile

If the site is very rocky, we drill a hole, install a reinforcement cage, and fill it with concrete. Yes, it's more expensive. Yes, it takes longer. But it's a guaranteed solution for difficult soils, especially for heavy structures.

Combined pile field

This is when some piles on a site are running smoothly, while others are struggling. The solution: mix pile types. Where they fit, we install helical piles. Where they don't, we drill and pour. The main thing is to calculate everything in advance with an engineer and not compromise the load-bearing capacity.