Evaluating Ground Reaction Curves from Single to Multiple Trapdoor Tests

Ground reaction curves (GRCs) are increasingly used to simulate the progressive development of soil arching resulting from differential movement in soil. In this study, 20 single, double, and multiple trapdoor tests were conducted under a simultaneous displacement mode (i.e., trapdoors settle simultaneously), while 8 double trapdoor tests were carried out under a successive displacement mode (i.e., trapdoors settle successively) to examine the evolution of soil arching including the parameters related to the GRCs. This study identified and analyzed the key parameters of the GRCs. For the trapdoor tests conducted under the simultaneous displacement mode, an increase of the fill height led to a decrease in the minimum pressure and its corresponding trapdoor displacement. Furthermore, the ultimate normalized pressure and recovery rate exhibited a decreasing trend with an increase of the fill height. As compared to the single and double trapdoor tests, the multiple trapdoor tests had similar initial soil arching, minimum normalized pressure, and its corresponding trapdoor displacement but a relatively lower stress recovery rate. In the trapdoor tests conducted with the successive displacement mode, the pressure on the first settled trapdoor decreased while it increased on the later settled trapdoor during the settlement of the first settled trapdoor. Conversely, during the settlement of the later settled trapdoor, the pressure on the first settled trapdoor increased, while it decreased on the later settled trapdoor. Analyzing the GRCs on the later settled trapdoor under the successive displacement mode revealed that the initial slope and ultimate pressure of the GRC decreased as the fill height increased.