The paper presents laboratory measurements of soil radial stress obtained in two parallel pile driving tests. The tests were designed to impose two modes of load to investigate the underlying mechanism of the radial stress buildup. Analyses on the test results indicated that soil pressure reached a peak before the pile's tip reached the depth of the pressure sensor. The buildup of soil pressure was closely related to the penetration depth of the pile. The soil pressure measured by the pressure sensors increased slowly and then dissipated during the pile installation process. Peak radial stress buildup in the vicinity of the pile tip remained higher than that in other places. In general, the peak radial stress reduced quickly in response to dynamic loading compared with the results obtained from press-in loading.