Frank Georg Schulz | TERRATEST

Procedure of Using A LWD for Testing the Bearing Capacity and Compaction Quality of Soil

Apr 23rd 2015 at 4:12 AM

A light weight deflectometer is a portable device that was developed in Germany for a more efficient and precise way to measure soil's compaction quality and bearing capacity. A LWD is useful when evaluating the degree of compaction in subsoil. Hence, it is ideal for quality control and quality assurance of the compaction of embankments, replacement fills, and soil-surfaced roads. It allows a dynamic test for mixed and coarse grained soils.

The bearing capacity pertains to the soil's ability to safely carry or support the pressure that will be placed on it from the engineered structure. The soil must be able to withstand the weight and pressure of the structure without causing any problems to the structure's form and installation. However, applying safe bearing pressure will not necessarily guarantee that the foundation's settlement will remain within certain acceptable limits. Hence, engineers must analyze the settlement, especially as many structures are typically sensitive to excessive settlement.

Bearing pressures that go beyond the limit of the soil's shear resistance will cause the structure to tilt or collapse. Bearing capacity failure can result to an extensive downward movement of the structure. The movement can typically be from 0.5 feet to more than 10 feet in magnitude, and this can occur within a day after the application of the first full load to the soil.

LWDs must be used continuously throughout the construction project to determine the soil's strength. Shear failure may sometimes influence the design of a structure to prevent large deformations in the soil before failure occurs. Differential movement and excessive settlement can lead to cracking and distortion of structures, loss of water retaining capacity and freeboard of dams and embankments, discomfort to occupants, structural failure, and misaligned operating equipment.

Various test methods can be used to determine the bearing capacity and compaction quality of soil. ASTM E2835-11 international standard LWDs provide a convenient method to test soil, with a calibration system that is accredited by the German Federal Road Research Institute. A high-quality LWD must have a weatherproof box and a large window with external controls and a GPS system that can provide satellite photo illustrations. One of the best LWDs has an integrated printer and USB flash drive. This way, you can easily print out the results or transfer them to your computer for analysis.

About The Author:

TERRATEST GmbH is world leader in development and manufacturing of Light Weight Deflectometers for dynamic load plate test. They offer the world’s first light weight deflectometerTERRATEST 5000 BLU” with Bluetooth and voice navigation. For more information about their products visit their website!

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