Soil testing equipment

The customer approached us with a request to develop a triaxial compression testing rig for soil analysis. The project required the design of both a stabilometer chamber and a load application system. The goal was to deliver a solution that provided a competitive edge while meeting the international standard for such tests—ISO 3601-2. Existing market alternatives could not operate at pressures as high as 16 atm. Additionally, the customer’s product team emphasized addressing user complaints about competitor solutions, particularly regarding the cumbersome and time-consuming process of loading soil samples. The presence of competitors also necessitated cost-efficient design and logistics to ensure the customer’s business model remained viable.

Stabilometer Chamber Design

The stabilometer chamber comprises a base, body, rod, upper and lower punches, drainage and pressure system pipelines, and an indicator. A critical design requirement was selecting a transparent material for the body capable of withstanding pressures of up to 16 atm. To ensure durability, we conducted computational simulations to test material strength and determine the optimal placement of the fixation mechanism. Ultimately, we selected a mineral glass tube, which outperformed other materials, such as acrylic glass, in terms of strength.

In existing market solutions, the chamber body is typically secured using bolts that attach a metal lid, a design that complicates soil sample loading, taking 4–5 minutes. To address this, we proposed using specialized latches mounted at the base, significantly simplifying the process. After a series of simulations, we optimized the geometry and placement of the locking mechanism, cutting the loading time in half and eliminating the need for wrenches.

Another key challenge was ensuring a reliable and cost-effective seal between the lower flange and the chamber base. We selected round-section O-rings that maintain a seal within a specific tolerance gap, balancing reliability and manufacturing costs.

For sealing the rod in the movable connection, we replaced traditional O-rings with rubber gaskets, which provided better durability and flexibility.

The secure attachment of the latex tubing for soil loading was also a priority. While rubber rings are commonly used in such chambers, the customer requested the use of clip fasteners. Standard clips failed to provide even pressure distribution, risking localized deformations and compromising the seal. To resolve this, our team designed a custom clip that ensured uniform contact, preventing leaks and maintaining integrity.

The chamber also includes a dedicated sleeve for connecting a temperature sensor.

To validate our design, we produced a stabilometer chamber prototype, which met all functional and performance requirements.

Load Application System Design

Upon completing the stabilometer chamber, we began designing the load application system, which is based on an electric drive. The system features two parallel jacks with gear reducers that apply the required loading force, mounted on a shared crossbeam. Feedback is provided by a load cell. The system is designed to accommodate a cylindrical load object with a diameter of 200 mm and a height of 280 mm between the actuators. Stepper motors were chosen to synchronize the movement of the parallel actuators, preventing misalignment under load.

Project Deliverables and Next Steps

We delivered the customer a complete set of engineering documentation for the load application system and a fully functional stabilometer chamber. The manufacturing of the load application system is currently underway—stay tuned for updates!