A reservoir employed trenchless horizontal directional drilling pipe installation method to construct a new bottom outlet. However

seepage issues emerged during the trial operation phase after the water storage resumed. Field excavation analysis indicated that the primary causes of seepage were non- standardized construction process control and insufficient pressure resistance of the PE pipe. PE pipe ruptured and collapsed when the external pressure exceeding the PE pipe′s strength

resulting in seepage. Based on this case

applicability of trenchless horizontal directional drilling pipe installation method constructing new bottom outlet is discussed. Considering its application to other reservoirs

it is concluded that trenchless horizontal directional drilling is feasible for constructing new bottom outlet in reservoir reinforcement projects

while continuous improvements in design and standardized construction practices are essential.