In order to understand the development

distribution and variation law of strain developed in a certain range of foundation soil near impact load

the dynamic response of the soil strain caused by balls falling from different heights was obtained by using fiber Bragg grating（FBG）technique.In the tests

the FBG strain sensors were horizontally embedded in a homogeneous continuous sand foundation with three layers.The results show that the soil strain experienced four stages:power law growth

linear growth

power law reduction（rebound）and residual strain（stability）.The peak strain moment in each group is highly consistent

which is about100 ms.The influence depth of the impact load is about 20 cm

which is 4 to 5 times of the ball diameter.Under the condition of the same FBG depth

the soil strain increases linearly with the increase of the falling height.Under the condition of the same falling height

the soil strain decreases exponentially with the FBG depth.The research results have certain guiding significance for revealing the mechanism of soil strain development

estimating the strength parameters of soil and further investigating on rapid determination of soil water content.