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1
Content available Numerical simulations of horizontal bearing performances of step-tapered piles
100%
Xiong L. , Chen H. , Xu Z. , Yang C.
Archives of Civil Engineering
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2021
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tom Vol. 67, nr 3
43--60
EN
In this study, we tried to understand the horizontal bearing performances of step-tapered piles using numerical simulations. The influence of the geometric parameters, e.g. the diameter (D) and the distance (L), and the length (H) of the pile were considered, and the soil distribution imposed on the horizontal bearing capacity of the piles was simulated. Numerical results show that when the other geometrical parameters of step-tapered piles are kept unchanged: (a) the increasing diameter (D) of the enlarged upper part of step-tapered piles improves the horizontal ultimate bearing capacity of step-tapered piles; (b) reduced distance (L) improves the horizontal ultimate bearing capacity of the step-tapered piles; (c) Increasing length (H) of the enlarged upper part of steptapered piles increases the horizontal ultimate bearing capacity; (d) the reduced length (H) decreases the bending moment of the pile body. Higher soil strength surrounding the enlarged upper part of step-tapered piles can increase the horizontal ultimate bearing capacity of step-tapered piles. The change of soil strengths at the end of the step-tapered piles does not influence the horizontal ultimate bearing capacity of step-tapered piles.
2
Content available Conventional triaxial loading and unloading test and PFC numerical simulation of rock with single fracture
100%
Tang Y. , Chen H. , Xiong L. , Xu Z.
Archives of Civil Engineering
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2024
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tom Vol. 70, nr 2
233--254
EN
Take the metamorphic sandstone as the reference object, by making rock like samples with fractures, the conventional triaxial loading and unloading test and PFC numerical simulation of rock like sample with single fracture were conducted, and the effects of the loading path, inclined angle of fracture, axial stress level during unloading, initial confining pressure during unloading on the compressive strength, peak strain and crack propagation evolution of the samples were considered. The compressive strength of the specimen under triaxial unloading is smaller than that under triaxial loading. The peak strain of the specimen under triaxial unloading is also smaller than that under triaxial loading. The specimen is more prone to brittle failure. When the axial stress level is the same during unloading, with the increase of the initial confining pressure during unloading, the difference of the compressive strength of the specimens with different inclined angles of fracture gradually decreases. Under the condition of uniaxial compression and triaxial compression, the failure of all specimens is tensile failure, and the shear failure is the main one during unloading.
3
Content available Uniaxial compression test and numerical simulation of rock-like specimen with T-Shaped cracks
100%
Liangxiao X. , Chen H. , Xu Z. , Hu D.
Archives of Civil Engineering
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2023
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tom Vol. 69, nr 2
227--244
EN
In this study, the uniaxial compression test and PFC2D numerical simulation were carried out on the artificial rock specimen with T-shaped prefabricated fractures. The effects of the lengths l1, l2 of the main fractures, the length l3 of the secondary fracture, and the angle β between the secondary fracture and the loading direction on the uniaxial compressive strength and crack evolution law of specimen were studied. The research results show that the change of l1, l2 and β has obvious effect on the compressive strength and crack growth of the specimen, but the change of l3 has little effect on the compressive strength of the specimen. When l3 = 40 mm and l1 ≠ l2, the angle β influences on the crack propagation and failure mode of the specimen.
4
Content available Experimental study on biaxial dynamical compressive test and PFC2D numerical simulation of artificial rock sample with single joint
88%
Liangxiao X. , Chen H. , Gao X. , Xu Z. , Hu D.
Archives of Civil Engineering
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2023
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tom Vol. 69, nr 1
213--229
EN
Dynamic biaxial compression tests and Particle Flow Code numerical simulations of the cement mortar specimens with a single joint were carried out to study the mechanical properties and crack evolution of artificial rock samples with a single joint. The effects of lateral stress σ2, loading rate V, the dip angle β (between the vertical loading direction and the joint) on the biaxial compressive strength σb, and the evolution law of crack were investigated. Test results showed that; (1) when both the dip angle β and the loading rate V remained unchanged, the biaxial compressive strength σb increased with the increase in the lateral stress σ2, while σ2 had no obvious effect on the crack evolution law; (2) when both the dip angle β and the lateral stress σ2 were kept unchanged, the loading rate V had an insignificant effect on the biaxial compressive strength σb and the crack evolution law; (3) when both the lateral stress σ2 and the loading rate V were constant, the biaxial compressive strength σb decreased first and then increased with the increase in the dip angle β; however, the dip angle β did not significantly affect the crack evolution law. The conclusions obtained in this paper are presented for the first time.
5
Content available Experimental study on shear mechanical properties of cement mortar specimen with through-step joints under direct shear
75%
Xiong L. , Chen H. , Guo H. , Mei S. , Xu Z. , Liu B.
Archives of Civil Engineering
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2022
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tom Vol. 68, nr 4
45--61
EN
In this study, direct shear tests were carried out on cement mortar specimens with single-ladder, single-rectangular, and double-rectangular step joints. Consequently, the shear strength, and crack shape of specimens with these through-step joints were analyzed, for understanding the influence of the through-step joint’s shape on the direct shear mechanical properties. The results of the investigation are as follows: (1) Under the same normal stress, any increases in the height h of the step joint causes an initial-increase-decrease in the shear strengths of specimens with single-ladder and double-rectangular step joints, causing a type-W variation pattern for the specimens with single-rectangular step joint. More essentially, when normal stress and h are constant, the shear strength of specimens with a single-ladder step joint is the greatest, followed by specimens with a double-rectangular step joint, and then specimens with a single-rectangular step joint is the least. (2) Furthermore, given a small h and low normal stress, specimen with a single-ladder step joint mainly experiences shear failure, whereas specimens with single-rectangular and double-rectangular step joints mainly generate extrusion milling in the step joints.
6
Content available Analysis of uniaxial compression of rock mass with parallel cracks based on experimental study and PFC2D numerical simulation
75%
Yang J. , Chen H. , Liangxiao X. , Xu Z. , Zhou T. , Yang C.
Archives of Civil Engineering
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2022
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tom Vol. 68, nr 1
111--128
EN
In this study, the uniaxial compression test and the numerical simulation of the two-dimensional particle flow code (PFC2D) were used to study the mechanical properties and failure laws of rock masses with parallel cracks. The experiment considers the influences of crack length (l), crack angle (β1L β2), and numerical changes in the rock bridge length (ℎ) and bridge angle (α) on failures of rock-like specimens. The results indicate that the uniaxial compressive strength (UCS) of the rock-like specimens with parallel cracks decreases with increasing l under different α values. The smaller angle between the preset crack and the loadinging direction (β) resulting in higher UCS. In addition, a larger ℎ results in higher UCS in the specimen. When β1 or β2 is fixed, the UCS and elastic modulus of the specimen show an ‘M’ shape with an increase in α. Moreover, the crack growth or failure mode of samples with different l values is similar. When β1 or β2 is small, the failure of the specimen is affected by the development and expansion of wing cracks. If one of β1 and β2 is large, the failure of the specimen is dominated by the expansion and development of the secondary cracks which is generated at the tip of the prefabricated crack. Furthermore, when the angle between the prefabricated crack and the loading direction is β1 = 0º, the rock bridge is less likely to reach penetration failure as ℎ increases. Secondary crack connections between the prefabricated cracks occur only when α is small.
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