A new method for measuring subgrade settlement in high-speed railway by using a linear CCD

With the rapid development of high-speed railway in China, measurements and controls of subgrade settlement have attracted much attention in recent years. A novel method to measure the subgrade settlement is proposed and a device has been developed. The device mainly contains a point light source and a point-position measurement device that uses a linear CCD to detect the position change of the point light’s image. Any position change of the point light source can be measured and the settlement for one point can be obtained remotely. The multi-point settlements can be obtained by using a series of such devices. Some methods such as self-calibration of the magnification, automatic background subtractions have been adopted to enhance the stability, adaptability and accuracy of the measurement system. The device has been used in some China high-speed railway sites and it has the advantages of high accuracy, low-cost and easy installation.

► A method to measure settlement with a linear CCD is presented.
► The measurement device is set on the reference pile which can be used as a datum.
► The multi-point settlements can be obtained by using a series of such devices.
► A comparison experiment was made in the national standardization laboratory.
► The measurement errors for the device developed were smaller than 0.09 mm.