performance of cells designed to measure soil pressure on earth retaining structures

as part of the trrl research programme to investigate the earth pressures developed against retaining structures, a laboratory study has been made of the performance of three types of pressure cell designed to measure the pressures developed at the boundary between the structural wall and the soil. the three cells tested were a hydraulic, a strain gauge and a pneumatic type pressure cell. the influence of soil type on cell calibrations was studied using washed sand, sandy clay and heavy clay. the relations between applied and recorded pressure for the three types of pressure cell are given for each soil type and the main factors influencing these relations are considered. the errors in cell registration were shown to depend not only on the physical properties of the soil and cell, but also on the nature of the compaction and testing procedure. the study has shown that suitable correction can be made for errors in cell registration provided laboratory calibrations of the pressure cells have been carried out in conditions which closely simulate the situations in which the instruments are to be employed. (a)