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Zheng J.-L.,Changsha University | Zheng J.-L.,Hunan Co innovation Center for Advanced Construction and Maintenance Technology of Modern Highway Infrastructure | Zhang R.,Changsha University | Zhang R.,Hunan Co innovation Center for Advanced Construction and Maintenance Technology of Modern Highway Infrastructure
Zhongguo Gonglu Xuebao/China Journal of Highway and Transport | Year: 2015

In order to provide reference for design and construction of expansive soil subgrade, methods for deformation calculation, compaction control and stiffness compensation of expansive soil subgrade were studied. One-dimensional swelling tests on three expansive soils were conducted. Based on the test results and moisture equilibrium rule of expansive soil subgrade, a new mathematics model for swelling and a method for deformation calculation of expansive soil subgrade were put forward. For the limitation of routine compaction control method on the expansive soil subgrade, a method for compaction control aimed at the maximum bearing capacity of expansive soil subgrade was proposed. According to the deflection equivalence of elastic double layer and elastic half space, a design method for stiffness compensation of expansive soil subgrade was suggested. The results show that the mathematics model can well reflect the ultimate swelling property and swelling deformation of expansive soil. Water content corresponding to the peak of variation curve of California Bearing Ratio with initial water content is close to natural water content of expansive soil and equilibrium water content of expansive soil subgrade. For compact expansive soil subgrade at this water content, the swelling of subgrade can be well controlled and the enough bearing capacity can be ensured. The stuffiness of expansive soil subgrade can be effectively increased to meet the requirement of pavement by filling nonexpansive soil in a certain thickness on the top of expansive soil subgrade. ©, 2015, Xi'an Highway University. All right reserved. Source


Deng Y.,Changsha University | Deng Y.,Hunan Co innovation Center for Advanced Construction and Maintenance Technology of Modern Highway Infrastructure | Li A.-Q.,Nanjing Southeast University | Liu Y.,Changsha University | Liu Y.,Hunan Co innovation Center for Advanced Construction and Maintenance Technology of Modern Highway Infrastructure
Zhendong Gongcheng Xuebao/Journal of Vibration Engineering | Year: 2015

Due to the randomness within the measured modal frequencies, the present study develops the probabilistic detection method for abnormal change of bridge structures' modal frequencies based on the theories of probability and statistics. The BPNN-based correlation models between modal frequencies and structural temperature are established, so as to eliminate the temperature effects in modal frequencies. Then the cumulative distribution functions of the modal frequencies after temperature effect eliminating are estimated using Kernel density estimation method. The estimated cumulative distribution functions are converted to Q statistics based on the inverse function of standard normal distribution. At last the mean value control charts of Q statistics are constructed to detect the abnormal change of modal frequencies. The hypothesis testing results show that Q statistics follow Gaussian distributions. Accordingly, the non-normality of modal frequencies with temperature effect elimination is handled to meet the requirement of random variables' normality in control charts. The results reveal that the probabilistic detection method of control chart have good sensitivity to the abnormal data of bridge's modal frequencies. The proposed method can provide a reference for the analysis and application of health monitoring data of long-span bridges. © 2015, Nanjing University of Aeronautics an Astronautics. All right reserved. Source

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