Water-Weakening Effects on the Mechanical Behavior of Different Rock Types: Phenomena and Mechanisms

Cai, Xun; Zhou, Zilong; Liu, Kewei; Du, Xueming; Zang, Haizhi

doi:10.3390/app9204450

Cited by 123 publications

(39 citation statements)

References 65 publications

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“…Традиционными способами изучения динамического механического поведения водонасыщенных материалов в условиях сжатия являются лабораторные эксперименты [16][17][18][19] и мониторинг крупномасштабных объектов, функционирующих в водонасыщенном состоянии [15,[20][21][22]. Перспективной альтернативой является компьютерное моделирование динамического нагружения представительных образцов бетонов с использованием связанных механических моделей, учитывающих деформацию каркаса, перераспределение (фильтрацию) порового флюида и взаимовлияние этих процессов.…”

Section: Introductionunclassified

The Numerical study of the influence of a two-scale pore structure on the dynamic strength of water-saturated concrete

Konovalenko

Сергеевич²,

Shilko

et al. 2020

PNRPU Mechanics Bulletin

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Many infrastructural concrete facilities, such as dams, bridge footings, foundations of port facilities and offshore drilling platforms, operate in a permanent contact with water. The permeable fractured-porous structure of concrete determines the water-saturated state of the surface layers of such concrete elements. Under dynamic contact loading, the pore fluid is capable of exerting a significant mechanical influence on the local stress-strain state and strength characteristics of the surface layers of concrete. This has to be taken into account when assessing the wear intensity of surface layers and predicting a concrete element’s service life. The aforesaid determines the relevance of the study aimed at identifying the influence of the pore fluid and characteristics of the concrete pore structure on the strength and fracture pattern under quasistatic and dynamic compressive loading. The present work is devoted to the theoretical study and generalization of the laws of mechanical influence of the pore fluid on the dynamic strength of high-strength concrete with a two-scale pore structure. The emphasis in the study is on analyzing the contributions of each of the pore subsystems to the integral mechanical effect of the fluid. To carry out such an analysis, a coupled hydromechanical model is developed. It takes into account the compositional structure of concrete, the presence of a pore space in a cement stone of two different scales, the interaction of a pore liquid and a solid-phase skeleton based on the Bio poroelasticity model, as well as fluid filtration in a pore space. By using the developed model were performed the numerical studies of the dependence between the compressive strength of the representative concrete volumes of the mesoscopic scale on the strain rate, the sample size, the pore fluid viscosity, and pore structure parameters. The simulation results showed the possibility of combining the obtained dependencies into a generalized (master) curve in terms of a combined dimensionless parameter, which has the meaning similar to the Darcy number. We identified two key factors that control the type and parameters of the concrete master curve of the dynamic strength. The first factor is the mobility of the pore fluid in the network of the capillary pores. It determines the rate of stress equalization in the porous skeleton due to fluid flow. The second factor is the interconnection of large micropores with the network of the small capillary pore channels. It determines the magnitude of the decrease in stress concentration in micropores by filtering the excess pore fluid into the capillary pore network. It is shown that the contributions of these two factors to the amplitude of variation of the dynamic strength of the water-saturated concrete are additive, and their total contribution reaches 25 %.

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Section: Introductionunclassified

The Numerical study of the influence of a two-scale pore structure on the dynamic strength of water-saturated concrete

Konovalenko

Сергеевич²,

Shilko

et al. 2020

PNRPU Mechanics Bulletin

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“…The porosity and water absorption were measured according to the procedures suggested by ISRM [40] after the end of every 10 frost cycles. The presence of water strongly influences rock materials properties [41]. For this purpose, the porosity and absorption of water was determined using the saturation technique.…”

Section: Porosity and Water Absorptionmentioning

confidence: 99%

Predicting Unconfined Compressive Strength Decrease of Carbonate Building Materials against Frost Attack Using Nondestructive Physical Tests

2020

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Carbonate building materials and engineering constructions are exposed to severe seasonal environmental fluctuations and result in a full or partial disintegration, especially in cold regions, and employment of nondestructive methods for evaluating the durability of building materials subject to frost weathering is gaining great significance. This research aims to obtain reliable relationships between unconfined compressive strength decrease and nondestructive parameters variations of limestone types under frost conditions and provide useful information regarding their durability in order to ensure the long-term viability or sustainability of these materials used for constructions against frost conditions. In this study, five important types of Chinese limestone used as construction materials were subjected to 50 frost cycles. Unconfined compressive strength, compressional wave velocity and spatial attenuation, and porosity were obtained at the end of every 10 cycles. As a result of progression in frost cycles, the increase and decrease rates were determined at the end of every 10 cycles, and the relationships between them were obtained to predict the loss ratios of unconfined compressive strength (RDσc). Results indicated that at the end of 40th cycles, there was a high correlation between RDσc and spatial attenuation loss with an R2 of 0.8584. Furthermore, there was also a strong relationship between RDσc and compressional wave velocity decrease after the end of 20th and 50th cycles with an R2 of 0.9089 and 0.9025, respectively. Therefore, these relations are reliable to provide useful information for durability and viability of studied samples under frost conditions and support the use of the ultrasonic measurements. It can also be successfully used for pre-estimation of unconfined compressive strength loss of studied limestone types against frost weathering without any tests.

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“…All samples were extracted from one single sandstone slab to minimize the variations in properties across the sample set [48]. Cylindrical samples 50 mm in diameter and 100 mm in length were first manufactured.…”

Section: Materials Characterization and Sample Preparationmentioning

confidence: 99%

Permeability Evolution of Fractured Rock Subjected to Cyclic Axial Load Conditions

et al. 2020

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Permeability experiments on saw-cut fractured rock subjected to cyclic axial load conditions were conducted on the MTS815 rock mechanics testing system. The influence of the frequency and amplitude of cyclic axial forces on axial displacement and permeability evolution of fractured rock was experimentally investigated. Results show that the increasing frequency under the same amplitude of axial load leads to a reduction in axial displacement, but a drop followed by an increase in permeability, while the permeability values oscillated sharply under high amplitude of cyclic loads, which can be attributed to the production of gouge materials. Besides, the increase in axial displacement roughly contributed to the permeability reduction, and excessive amplitude of cyclic load posed limited boost to the permeability enhancement. By comparing with the quasistatic function, we found that it did not completely correspond to the trend of the permeability evolution subjected to cyclic axial forces, and sensitivity coefficients evolving with frequency and amplitude should be considered. A new function of the permeability evolution subjected to the amplitude and frequency of cyclic axial forces was derived and verified by the experimental data. This study suggests that small amplitude and high frequency of dynamic forces have the potential for enhancing the permeability of fracture and triggering the disaster of fractured rock.

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Water-Weakening Effects on the Mechanical Behavior of Different Rock Types: Phenomena and Mechanisms

Cited by 123 publications

References 65 publications

The Numerical study of the influence of a two-scale pore structure on the dynamic strength of water-saturated concrete

The Numerical study of the influence of a two-scale pore structure on the dynamic strength of water-saturated concrete

Predicting Unconfined Compressive Strength Decrease of Carbonate Building Materials against Frost Attack Using Nondestructive Physical Tests

Permeability Evolution of Fractured Rock Subjected to Cyclic Axial Load Conditions

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