One trench for agricultural irrigation next to the Hu-Ning Intercity Railway viaduct section were tested and analyzed in order to achieve the effect of ground vibration isolation when CRH trains run on.The result shows that with decrease of train speed

the peak value of ground vibration velocity decreases and the main frequency of ground vibration heightens.The trench has lowpass filtering effect on ground surface vibration.The slower the train speed

the more apparent the effect of isolation

but the phenomenon that ground surface vibration increases before trench is more remarkable.When the length of trench is much greater than the length of train

the number of carriages has little effect on vibration isolation effect of the trench.When the railways are built

the department concerned should facilitate the coordination with nearby residents and department of agriculture

and the trench’s length

depth

breadth and the distance to railway should be designed reasonably.And then the trench in addition to meet the need of irrigation

but also has marked effect on vibration isolation.