The scope of the study was aimed to observe the long-term static load of the L-shaped retaining walls incorporated with fiber optic geogrid using Brillouin optical time-domain reflectometry method at the interval of 55 mm installed with short wooden pile of small diameter. The application of wooden pile in soft ground using the bottom panel system structure of the foundation has been discussed based on the published construction manual referred to the waterway box culvert and pre-cast L-shaped retaining walls to reduce the load on the short wooden pile head using geogrid. The actual vehicle dump truck was used to measure loads passing through the retaining wall after 160 days of construction. The results showed that the load acting on the pile increases with time and approached the allowable bearing capacity of 28.9 kN/pile group. The straining immediate after the construction was detected to be decreased after four months due to stress relaxation on the geogrid. The strain under static live load under a rear wheel of the dump truck to a virtual rear portion of L-shaped retaining wall and at the central portion of the bottom panel width of L-shaped retaining wall yielded the tensile straining in the periphery. It is found that the straining on geogrid is relatively small to be able for bearing the load of the dump truck to some extent.