Investigation of less temperature-sensitive Fiber Bragg Grating strain sensor in pile jacking field test

It is well known that two main parameters affect the penetration characteristics of the jacked pile in saturated clay soil area. One is soil breaking resistance at pile end. The other is sliding friction between the pile and soil. In order to study the variation law of pile end resistance with penetration depth in saturated clay, a full-scale in-situ test was conducted. In this test, the less temperature-sensitive gripper jacked pile monitoring system was used. Through the application of this monitoring system, the variation law of pile end resistance with penetration depth was obtained successfully. The test results showed that (1) Based on the field test of two closed-end jacked piles, the feasibility of the developed monitoring system is verified; (2) It is found that the hardness of soil and the change of soil have significant influence on the pile end resistance. (3) When the pile end enters the silty clay layer from the silty clay layer, the pile end resistance increases obviously, and the rapidly growing depth is around 3d (where d is the pile diameter). Based on FBG, the less temperature-sensitive monitoring system provides a feasible and effective method for the field monitoring of pile jacking. •This paper presents a jacked pile monitoring system based on less temperature-sensitive FBG sensor.•The pile end resistance of jacked pile is studied by field test.•The pile end deformation can be considered as the axial deformation of the clamping support.•The internal relationship between pile end resistance and soil distribution is deeply analyzed.