An IoT-enabled penetrometer with constant-rate penetration for accurate measurement of soil cone index

Abstract

Hand-pushed cone penetrometer has been utilized to assess soil compaction based on soil penetration resistance (SPR). However, the manual operation of these devices can be quite challenging and erroneous. The accuracy of the data gathered using such devices can be hindered by the operator’s limitation in maintaining a constant-rate of penetration into the soil, thus preventing the attainment of a steady, predefined penetration rate. To address this issue, a constant-rate, IoT-enabled cone penetrometer is designed and constructed. The developed penetrometer measures the SPR across the soil profile with a designed lead screw arrangement that ensures a constant-rate penetration. The device comprises a mechanical system and an electronic control unit that utilizes IoT framework. The mechanical system includes a primary frame, lead screw arrangement and a standard penetrometer probe. The SPR, and depth along with coordinates of location are measured and stored on a web server. A user-friendly customizable web interface and mobile application enable real-time access. The developed penetrometer measures the SPR up to 2000 kPa up to 400 mm depth. Comparative analysis shows that the constant-rate penetrometer (CRP) provides more reliable and less variable resistance measurements compared to the hand-pushed penetrometer (HPP), with significant differences observed at multiple depths. This penetrometer maintains a constant-rate of penetration, ensuring adherence to predefined standards for accurate measurements.

Keywords

• Cone penetrometer
• internet of things
• soil penetration resistance
• constant-rate penetration
• cone index
• ASABE