Instrumentation Selection Criteria for Field Monitoring of Retaining Systems

In today’s technology era, many alternatives are available for measuring soil and structural response, and direct measurement in-situ using instruments/sensors is the best option among several alternatives. Proper selection of instrumentation for any field test is essential to obtain reliable data. The present paper discusses the instrumentation plan adopted for a field test that was conducted to assess the suitability of geofoam as a compressible inclusion material in retaining walls. The compressible inclusion is a material that is introduced between the wall and backfill which deforms in a controlled manner allowing the soil to change its stress state from at-rest to active or near-active state, causing lateral pressure reduction on the wall. The field testing aimed to measure the earth pressure on the wall, wall deflection, and compression of the geofoam. The options available for measuring each of these parameters, such as earth pressure cells and their type, inclinometer, displacement transducers, etc., are analyzed with the criterion for selecting the right instrument for measuring each parameter. Each instrument has its challenges and some of these challenges encountered during field testing are discussed in detail about earth pressure cells and inclinometers. To make sense of the data obtained by instruments, the user must have some secondary measurement tools to justify the data obtained by primary instruments.