A statistical damage constitutive model under freeze-thaw and loading for rock and its engineering application

冻融和加载条件下岩石统计损伤本构模型及其工程应用

Cold Regions Science and Technology, Volume 145, January 2018, Pages 142-150

Shibing Huang, Quansheng Liu, Aiping Cheng, Yanzhang Liu

摘要：The freeze-thaw damage of rock is a critical problem to study rock engineering in cold regions. When water is frozen in pores, 9% volume expansion will induce damage in rock for a huge ice pressure. Thus, rock will be deteriorated and softened after freeze-thaw. Besides, loading damage produces when the inner stress exceeds the bearing capacity of rock. So it's crucial to establish a damage constitutive model under freeze-thaw and loading in order to evaluate the stability of rock engineering in cold regions. The freeze-thaw damage of rock is expressed by static elastic modulus in this paper, which can be accurately and simply predicted by damage evolution equation using P-wave velocity or compression strength proposed by Liu et al., 2015. Loading damage can be obtained by statistical theory assuming that micro-unit strength satisfies the Weibull distribution and the maximum-tensile-strain yield criterion. Then the final statistical damage constitutive equation under freeze-thaw and loading is derived, in which unknown parameters can be determined through carrying out compression experiment on rock after different freeze-thaw cycles. This developed model is validated by a previous experiment and applied to analyze the stability of a tunnel under coupled thermo-hydro-mechanical condition in cold regions. The results show that the proposed constitutive model is very suitable for rock suffering freeze-thaw cycles and it is of high accuracy and good practicality.

A statistical model for predicting the triaxial compressive strength of transversely isotropic rocks subjected to freeze–thaw cycling

冻融循环条件下横观各向同性岩石三轴压缩强度估算统计模型

Cold Regions Science and Technology, Volume 145, January 2018, Pages 237-248

Helin Fu, Jiabing Zhang, Zhen Huang, Yue Shi, Wei Chen

摘要：Freeze–thaw damage to rock masses is one of the most significant durability problems in many regions worldwide. This study conducts triaxial compression tests to experimentally investigate the strength properties of freeze–thawed core samples of Carboniferous slates with bedding angles of 30°, 45°, 60°, and 75° under different confining pressures. The triaxial compressive strength decreases as the number of freeze–thaw cycles increases, continuously increases with increasing confining pressure, and initially decreases and then increases as the bedding angle increases from 30° to 75°. Additionally, to satisfy the requirements of engineering projects in cold regions, a statistical model is proposed to predict the triaxial compressive strength of freeze–thawed transversely isotropic rocks based on the single discontinuity theory. In this model, the cohesive strength and angle of internal friction of the discontinuity are assumed to be functions of the number of freeze–thaw cycles. The validity and accuracy of this model are verified by comparing the results of the proposed model with those of the experiments. It is found that the model can correctly describe the influences of the number of freeze–thaw cycles, confining pressure, and bedding plane orientation on the triaxial compressive strength of freeze–thawed transversely isotropic rocks.

Influence of physical and mechanical properties on the durability of limestone subjected to freeze-thaw cycles

冻融循环条件下石灰石物理和力学特性对其耐久性的影响

Construction and Building Materials, Volume 162, 20 February 2018, Pages 420-429

Javad Eslami, Charlotte Walbert, Anne-Lise Beaucour, Ann Bourges, Albert Noumowe

摘要：The frost sensitivity of five French limestones (Massangis (MA), Lens (LS), Savonnières (SA), Saint-Maximin (MX) and Migné (MI)), with different physical and mechanical properties, was studied. The total porosity ranges from 10% to 35% and the uniaxial compressive strength ranges between 10 MPa and 60 MPa. The freeze-thaw tests were applied on the samples saturated in natural condition. During freeze-thaw cycles we recorded the evolution of temperature and volumetric strain of a specimen for each stone and after the freeze-thaw cycles, the weathering evolution in stone samples was monitored by measurement of different physical and mechanical parameters (porosity, P-wave velocity, fracture toughness, compressive strength and elastic static modulus). Two behaviors were observed: a volumetric expansion during freezing phase accompanied by a very important damage from the first cycle until the failure of specimen for MI and MX stones, and a volumetric contraction accompanied with a light damage for the high number of freeze-thaw cycle in the cases of MA, LS and SA. Following the freeze–thaw tests, the durability of stones was evaluated using a decay function model. The decay constant values determined from the evolution of P-wave velocity were correlated with different fresh stone properties. Contrary to generally accepted ideas, the correlation coefficients between the decay constant and total porosity or degree of saturation are very low. Porosity in natural condition seems to have the strongest influence on the decay constant. However, its negative impact can be offset by a bigger part of trapped porosity. The results indicate that it is possible to predict the frost damage of the stones, with a better level of confidence, from the ratio of the volume fraction of water to that of air rather than from only the total porosity or degree of saturation.

Effects of the incorporation of recycled aggregate in the durability of the concrete submitted to freeze-thaw cycles

冻融循环条件下再生骨料掺和对混凝土耐久性的影响

Construction and Building Materials, Volume 161, 10 February 2018, Pages 723-730

N.S. Amorim Júnior, G.A.O. Silva, D.V. Ribeiro

摘要：Recycled concrete aggregates have been extensively studied in recent years. However, the studies that have addressed the use of the recycled aggregate in concrete subjected to freeze-thaw cycles are divergent. Thus, the present work suggests the use of recycled coarse aggregate (RCA), derived from civil construction waste, in concrete as a substitution to the natural coarse aggregate (NCA). To this end, concrete specimens were molded with replacement levels equal to 15%, 25% and 50% of the NCA for RCA, being the specimens evaluated according to the ASTM C 666-15 norm. In addition, the samples were characterized for apparent porosity and density, water absorption by capillarity, axial compression strength and dynamic modulus of elasticity. The use of recycled aggregates proved to be efficient as a possible alternative to the incorporation of air in the concretes, presenting a durability factor at the end of the cycle higher than presented by the reference mixture.

Compressive failure characteristics of yellow sandstone subjected to the coupling effects of chemical corrosion and repeated freezing and thawing

化学腐蚀和循环冻融耦合效应下黄沙石的压缩破坏特征

Engineering Geology, Volume 233, 31 January 2018, Pages 160-171

Xinyu Fang, Jinyu Xu, Peixi Wang

摘要：The coupling effects of chemical corrosion and freeze-thaw (F-T) cycling on the compressive failure characteristics of yellow sandstone were investigated. Results show that both chemical corrosion and minimum temperature in F-T cycles have adverse effect on the mechanical properties of yellow sandstone. With decreasing minimum F-T temperature and pH of the corrosive solution, peak stress and elastic modulus both decrease while peak strain increases, illustrating that the bearing capacity and deformation resistant capacity both decrease while ductility increases. During UCS tests, less damaged samples with a lower porosity tend to exhibit double-cone failure and contain smaller pores and more trans-grain fractures. Higher-damage samples with higher porosity tend to exhibit split failure or slope failure and contain larger pores and more inter-grain fractures. Chemical reactions between yellow sandstone and various chemical solutions are analyzed. F-T damage primarily occurs during freezing while chemical corrosion primarily occurs during thawing. Additionally, both the friction state and the internal microstructural damage influence the final failure mode. Results of this work can provide reference for the construction and development of rock structures in cold regions.