What is a Borehole Inclination Test and Why is BIT Trusted Worldwide

Understanding the vertical alignment of drilled shafts and boreholes is crucial in deep-foundation construction. Even the smallest deviation in angle can affect load capacity, durability, and structural safety. That is why professionals across the globe rely on the Borehole Inclination Tester (BIT) — which uses very accurate gyro. This gyro based highly accurate method for verifying the verticality of boreholes before concrete placement.

The BIT Borehole Inclination Tester has become a global benchmark in the industry. Its advanced sensors, easy field deployment, and precise reporting help engineers ensure boreholes and piles are drilled exactly as designed. This article explains what a borehole inclination test is, why it matters, and why the BIT system is trusted worldwide.

What Is a Borehole Inclination Test?

A borehole inclination test measures the deviation of a drilled shaft or borehole from its intended vertical alignment. During pile construction, drilling tools can shift due to soil conditions, obstructions, or equipment vibration. Without monitoring verticality, the pile may not function as expected.

A borehole inclination test provides quantitative measurements of:

• Borehole deviation in degrees

• Direction of inclination

• Change in direction with depth

This data helps engineers confirm that the foundation element is structurally sound and meets design specifications before concrete is poured.

Why Borehole Verticality Matters in Deep-Foundation Engineering

Vertical accuracy isn’t merely a formality—it directly influences the overall performance and safety of a structure. When a pile or borehole deviates from its intended vertical path, even by a few centimeters over several meters of depth, the alignment of the entire foundation system can be compromised. This small deviation increases structural risk and affects long-term reliability.

Poor verticality can lead to uneven load transfer from the superstructure to the soil, causing higher stress concentrations in certain areas. It can also reduce the durability of the pile due to eccentric stresses and introduce misalignment between multiple piles in a group foundation. Over time, these issues may escalate into settlement problems, cracking, or even structural instability.

In critical structures such as bridges, high-rise buildings, power plants, and offshore infrastructure, the cost of failure is massive—not only in terms of repairs, but also safety and operational disruption. This makes the verification of borehole verticality a non-negotiable requirement. Using a precise and reliable technology like the BIT (Borehole Inclination Tester) ensures that foundations meet engineering tolerances from the very start, minimizing long-term risk and maximizing structural performance.

In a case of retaining walls, such as pile walls and secant walls, misalignment can cause two major issues

1 – it can create a gap between the piles, which translate to a hole in the retaining wall, that can cause underground water penetration to the construction area (I,e, basement, parking lots etc)2 – It can cause the retaining wall to penetrate the planed underground floors, and reduce the effective available area (i.e. reduce the number of parking lots)

This picture presents how misaligned piles have penetrated the drive way of a parking lot.

How the BIT System Performs Borehole Inclination Testing

The BIT Borehole Inclination Tester uses highly sensitive gyro sensors and an automated digital recording unit. The process is quick, safe, and does not require post-processing once the data log is completed. It also requires a centralized to keep the sensor at a known fixed position vs the borehole. The centralizer can be the drill bucket of the borehole drill machine or a custom made or purchased from Piletest. The sensor is than attached to the centralizer before the test begins

General Workflow

1. Insert the BIT probe + centralizer into the borehole

2. Lower the probe to the bottom and collect inclination measurements at multiple depths (controlled by the BIT software)

3. Do the same at same measurement locations controlled by the BIT software app, during retrieval

Once the probe reaches the surface, the software automatically converts the measurements into a detailed verticality profile.

The BIT vertical profile

The BIT top view of borehole position

Key Strengths of the BIT System

·         No need for casing.

·         Borhole can be wet or dry

·         Fast measurement cycle, saving site time

·         Highly repeatable results

·         Single person operation (saves man power and cost)

The combination of dependable sensors and user-friendly software makes BIT efficient even under challenging site conditions.

BIT System components

1 – BIT system

2 – Sensor

3 – Wireless Depth meter

4 - Android tablet or Smartphone

BIT vs Traditional Verticality Measurement Methods

A comparison makes it easier to understand why BIT is increasingly preferred.

Aspect	Traditional Manual Methods	Sonic method	BIT Borehole Inclination Tester
Accuracy	Low	High	High
Speed	Slow	Needs a crane	Fast
Data Format	Manual & estimated	Digital	Digital, precise & exportable
Depth Suitability	Limited	Suitable only for deep DRY shafts	Suitable for deep shafts
Reporting	Handwritten notes	Computerized report	Windows Word editable reports
Training Requirements	High	High	Minimal
Field Reliability	Affected by environment	Stable	Stable & consistent

Traditional methods often require interpretation, which can introduce human error. BIT removes guesswork and increases confidence in quality assurance.

Where Borehole Inclination Testing Is Required

BIT is widely used across deep-foundation and geotechnical projects where precision is critical. Its applications span pile foundations for bridges and metro systems, drilled shafts for industrial structures and towers, and retaining walls supported by secant or contiguous piles. In every scenario where vertical alignment determines the performance and safety of a structure, BIT serves as the trusted solution—ensuring that foundations are built with confidence and meet engineering tolerances from the very beginning.

How Borehole Deviation Affects Pile Performance

When a pile deviates from its intended position, the resulting stresses become uneven, causing the pile to take either more or less load than originally designed. This imbalance directly compromises long-term structural stability and reduces the efficiency of the foundation system. Deviation typically leads to three core effects: a reduction in load-bearing capacity because compressive forces no longer align with the pile center, increased material consumption as designers must over-engineer to account for uncertainties, and alignment conflicts where pile heads no longer match the pile cap grid layout.

BIT effectively addresses these risks by delivering accurate and reliable borehole inclination measurements before the structure is finalized. By confirming verticality early, project teams can avoid costly design modifications, prevent structural misalignment, and ensure that piles perform as intended throughout their service life.

Why BIT Is Trusted Worldwide for Deep-Foundation QA/QC

BIT is considered a global leader because it meets the field needs of modern contractors and consultants.

Technical Advantages

• Real-time deviation tracking against depth

• High-sensitivity digital inclination sensor

• Rugged probe design suitable for harsh drilling sites wet and dry boreholes

Operational Advantages

• Easy to handle by one technician

• Short learning curve

• Fast reporting, making inspection approvals quicker

• Simple design and low weight makes for fast setup on the construction site

Project Advantages

• Reduces re-drilling risks

• Ensures compliance with engineering standards

• Improves long-term structure reliability

For contractors, BIT contributes directly to safety, savings, and better project timelines.

Who Benefits Most from Borehole Inclination Testing?

While useful across the construction pipeline, the test benefits different groups in distinct ways:

Students and Junior Engineers

Gain practical understanding of foundation QA/QC and geotechnical measurements.

Clients and Project Owners

Get confidence that foundations are being installed precisely as designed.

Contractors and Site Engineers

Improve productivity and avoid costly rework due to undetected deviations.

The universality of these benefits explains the global adoption of BIT across both small and large projects.

Conclusion

The Borehole Inclination Test plays a crucial role in ensuring the safety and performance of deep-foundation structures. As construction demands grow in scale and complexity, maintaining exact borehole verticality is more important than ever. The BIT Borehole Inclination Tester has emerged as the global standard because it delivers unmatched accuracy, speed, and reliability—exactly what modern engineering requires.

Whether you're a student learning the fundamentals or a project manager overseeing complex builds, BIT provides clarity, assurance, and measurable quality for every borehole drilled.

instead of magnetic field (like compass) based products, that are affected from metal tubes and piles or mechanical wheels in specially grooved tubes

Frequently asked questions

What does a borehole inclination test measure?

It measures the deviation and direction of the borehole from vertical alignment from top to bottom.

Can BIT be used in uncased boreholes?

Yes, BIT works in both cased and uncased boreholes in wet or dry boreholes .

How deep can BIT measure?

The system is suitable for deep drilled shafts used in large infrastructure projects.(150 meters)

How long does the inclination test take?

Typically 10-20 minutes per borehole, including logging and reporting.

Is special training needed to operate BIT?

No, the system is designed for fast learning and simple operation in the field.