A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Long-term behaviour and degradation of calcareous sand under cyclic loading
Abstract Calcareous sand has been used as the main filling material in numerous reef constructions. Therefore, understanding its long-term dynamic engineering geological characteristics under cyclic applications of traffic or wave loading is crucial to the design and prediction of the serviceability of reef infrastructures. Considering this, seven monotonic triaxial tests and 33 high-cycle (25,000 cycles) drained triaxial tests were conducted on calcareous sand with various mean effective stresses (p’) and cyclic stress ratios (ζ). The results show that the development of the accumulated axial strain (ε 1 acc) has a strong correlation with the positional relationship between the cyclic stress path and critical strength line (CSL) or static strength envelope (SSE) in the p’-q plane. The critical cyclic stress ratio ζ c, that represents the cyclic stress path reaching the CSL, is proposed. When ζ>ζ c, the growth rate of ε 1 acc with ζ increases drastically. Moreover, when the cyclic stress path approaches the SSE, ε 1 acc enters an incremental collapse state. The increase in p’ diminishes the dilatancy of the volumetric strain ε v. However, this response of ε v reverses from decreasing to increasing with increasing ζ. The resilient modulus (M r) increases with the number of cycles (N) due to the initial densification. If ε v dilation occurs, M r will decrease with N as particles lose contact. A single parameter for the cyclic stress path ratio (ψ) considering the effects of p’, ζ, and SSE is proposed. Additionally, empirical formulas for calculating the ultimate ε 1 acc and M r are established. Furthermore, particle degradation significantly worsens ε 1 acc and ε v, but has a more profound effect on the compressibility of ε v. This degradation is also detrimental to M r. A certain deviation trend of the predicted values from the measured values is found to correspond with the relative particle breakage.
Highlights The effect of the relationship between cyclic stress path and static shear state lines on accumulated strain was analysed. The reverse cyclic stress ratio marks the threshold stress that changes dilatancy from decreasing to increasing. Empirical models for predicting ultimate accumulated axial strain and resilient modulus were established. The degradation along with its effect on long-term cyclic behaviour was discussed. A certain deviation trend of predicted values from measured values was found to have a connection with particle breakage.
Long-term behaviour and degradation of calcareous sand under cyclic loading
Abstract Calcareous sand has been used as the main filling material in numerous reef constructions. Therefore, understanding its long-term dynamic engineering geological characteristics under cyclic applications of traffic or wave loading is crucial to the design and prediction of the serviceability of reef infrastructures. Considering this, seven monotonic triaxial tests and 33 high-cycle (25,000 cycles) drained triaxial tests were conducted on calcareous sand with various mean effective stresses (p’) and cyclic stress ratios (ζ). The results show that the development of the accumulated axial strain (ε 1 acc) has a strong correlation with the positional relationship between the cyclic stress path and critical strength line (CSL) or static strength envelope (SSE) in the p’-q plane. The critical cyclic stress ratio ζ c, that represents the cyclic stress path reaching the CSL, is proposed. When ζ>ζ c, the growth rate of ε 1 acc with ζ increases drastically. Moreover, when the cyclic stress path approaches the SSE, ε 1 acc enters an incremental collapse state. The increase in p’ diminishes the dilatancy of the volumetric strain ε v. However, this response of ε v reverses from decreasing to increasing with increasing ζ. The resilient modulus (M r) increases with the number of cycles (N) due to the initial densification. If ε v dilation occurs, M r will decrease with N as particles lose contact. A single parameter for the cyclic stress path ratio (ψ) considering the effects of p’, ζ, and SSE is proposed. Additionally, empirical formulas for calculating the ultimate ε 1 acc and M r are established. Furthermore, particle degradation significantly worsens ε 1 acc and ε v, but has a more profound effect on the compressibility of ε v. This degradation is also detrimental to M r. A certain deviation trend of the predicted values from the measured values is found to correspond with the relative particle breakage.
Highlights The effect of the relationship between cyclic stress path and static shear state lines on accumulated strain was analysed. The reverse cyclic stress ratio marks the threshold stress that changes dilatancy from decreasing to increasing. Empirical models for predicting ultimate accumulated axial strain and resilient modulus were established. The degradation along with its effect on long-term cyclic behaviour was discussed. A certain deviation trend of predicted values from measured values was found to have a connection with particle breakage.
Long-term behaviour and degradation of calcareous sand under cyclic loading
He, Shao-Heng (author) / Ding, Zhi (author) / Xia, Tang-Dai (author) / Zhou, Wan-Huan (author) / Gan, Xiao-Lu (author) / Chen, Yong-Zhan (author) / Xia, Fan (author)
Engineering Geology ; 276
2020-07-07
Article (Journal)
Electronic Resource
English