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Uniaxial compression test and numerical simulation of rock-like specimen with T-Shaped cracks

Xiong Liangxiao Haijun Chen Zhongyuan Xu Deye Hu
Archives of Civil Engineering | 2023 | vol. 69 | No 2 | 227-244 | DOI: 10.24425/ace.2023.145265
Keywords artificial rock specimen T-Shaped crack Uniaxial compression test
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Abstract

In this study, the uniaxial compression test and PFC 2D 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.
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Authors and Affiliations

Xiong Liangxiao
1
ORCID: ORCID
Haijun Chen
2
ORCID: ORCID
Zhongyuan Xu
3
ORCID: ORCID
Deye Hu
1
ORCID: ORCID
  1. School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, China
  2. Geotechnical Engineering Department, Nanjing Hydraulic Research Institute, Nanjing, 210029, China
  3. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China

Numerical simulations of horizontal bearing performances of step-tapered piles

Liangxiao Xiong Haijun Chen Zhongyuan Xu Changheng Yang
Archives of Civil Engineering | 2021 | vol. 67 | No 3 | 43-60 | DOI: 10.24425/ace.2021.138042
Keywords Step-tapered piles horizontal bearing performance numerical simulation geometric size soil distribution
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Abstract

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.
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Bibliography


[1] M. Ghazavi, O. Tavasoli, “Characteristics of non-uniform cross-section piles in drivability”, Soil Dynamics and Earthquake Engineering 43: pp. 287–299, 2012.
[2] A.M. Rybnikov, “Experimental investigations of bearing capacity of bored-cast-in-place tapered piles”, Foundation Engineering 43: pp. 48–52, 1990.
[3] K.K. Jayantha, D.M. Ian, “Axial response of tapered piles in cohesive frictional ground”, Journal of Geotechnical and Geoenvironmental Engineering 119: pp. 675–693, 1993.
[4] M. Sakr, M.H. El Naggar, M. Nehdi, “Wave equation analyses of tapered FRP–concrete piles in dense sand”, Soil Dynamics and Earthquake Engineering 27: pp. 166–182, 2007.
[5] J.H. Lee, K.H. Paik, D.H. Kim, S.H. Hwang, “Estimation of axial load capacity for bored tapered piles using CPT results in sand”, Journal of Geotechnical and Geoenvironmental Engineering 135: pp. 1284–1294, 2009.
[6] Y.G. Zhan, H. Wang, “Numerical study on load capacity behavior of tapered pile foundations”, Journal of Geotechnical and Geoenvironmental Engineering 17: pp. 1969–1980, 2012.
[7] G.Q. Kong, H. Zhou, H.L. Liu, X.M. Ding, R. Liang, “A simplified approach for negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge”, Journal of Central South University of Technology, 21: pp. 3648–3655, 2014.
[8] N. Hataf, A. Shafaghat, “Optimizing the bearing capacity of tapered piles in realistic scale using 3D finite element method”, Geotech Geol Eng 33: pp. 1465–1473, 2015.
[9] F.I. Nabil, “Behavior of step tapered bored piles in sand under static lateral loading”, Journal of Geotechnical and Geoenvironmental Engineering 136: pp. 669–676, 2010.
[10] Y.R. Lv, H.L. Liu, X.M. Ding, G.Q. Kong, “Field tests on bearing characteristics of x-section pile composite foundation”, Journal of Performance of Constructed Facilities 26: pp. 180–189, 2012.
[11] L.X. Xiong, H.J. Chen, “A numerical study and simulation of vertical bearing performance of step-tapered pile under vertical and horizontal loads”, Indian Geotech J 50: pp. 383–409, 2020.
[12] N.F. Ismael, “A behavior of laterally loaded bored piles in cemented sands”, Journal of Geotechnical Engineering 116: pp. 1678–1699, 1990.
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Authors and Affiliations

Liangxiao Xiong
1
ORCID: ORCID
Haijun Chen
2
ORCID: ORCID
Zhongyuan Xu
3
ORCID: ORCID
Changheng Yang
1
ORCID: ORCID
  1. School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, PR China
  2. Geotechnical Engineering Department, Nanjing Hydraulic Research Institute, Nanjing, Jiangsu Province, 210029, PR China
  3. Department of Earth Sciences, University of Delaware, DE 19716, United States

Experimental study on shear mechanical properties of cement mortar specimen with through-step joints under direct shear

Liangxiao Xiong Haijun Chen Haogang Guo Songhua Mei Zhongyuan Xu Bin Liu
Archives of Civil Engineering | 2022 | vol. 68 | No 4 | 45-61 | DOI: 10.24425/ace.2022.143025
Keywords artificial rock specimen ladder step joint rectangular step joint height of step joint shear strength
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Abstract

In this study, direct shear tests were carried out on cement mortar specimens with singleladder, 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-Wvariation 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 smallℎ 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.
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Authors and Affiliations

Liangxiao Xiong
1
ORCID: ORCID
Haijun Chen
2
ORCID: ORCID
Haogang Guo
3
ORCID: ORCID
Songhua Mei
1
ORCID: ORCID
Zhongyuan Xu
4
ORCID: ORCID
Bin Liu
5
ORCID: ORCID
  1. Hunan Provincial Key Laboratory of Hydropower Development Key Technology, Power China Zhongnan Engineering Corporation Limited, Changsha 410014, China
  2. Geotechnical Engineering Department, Nanjing Hydraulic Research Institute, Nanjing, 210029, China
  3. Civil and Environmental Engineering Department, Carnegie Mellon University, Pittsburgh 15289, United States
  4. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China
  5. School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, China

Experimental study on biaxial dynamical compressive test and PFC2D numerical simulation of artificial rock sample with single joint

Xiong Liangxiao Haijun Chen Xinghong Gao Zhongyuan Xu Deye Hu
Archives of Civil Engineering | 2023 | vol. 69 | No 1 | 213-229 | DOI: 10.24425/ace.2023.144169
Keywords artificial rock specimen biaxial dynamic compression compressive strength crack evolution aw
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Abstract

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 𝜎 b, and the evolution lawof crackwere investigated. Test results showed that; (1) when both the dip angle β and the loading rate V remained unchanged, the biaxial compressive strength 𝜎 b 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 𝜎 b and the crack evolution law; (3) when both the lateral stress 𝜎2 and the loading rate V were constant, the biaxial compressive strength 𝜎 b 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.
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Authors and Affiliations

Xiong Liangxiao
1
ORCID: ORCID
Haijun Chen
2
ORCID: ORCID
Xinghong Gao
3
ORCID: ORCID
Zhongyuan Xu
4
ORCID: ORCID
Deye Hu
1
ORCID: ORCID
  1. School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, China
  2. Geotechnical Engineering Department, Nanjing Hydraulic Research Institute, Nanjing,210029, China
  3. China Construction Third Bureau First Engineering Co., Ltd., Wuhan 430040, China
  4. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China

Analysis of uniaxial compression of rock mass with parallel cracks based on experimental study and PFC2D numerical simulation

Jie Yang Haijun Chen Xiong Liangxiao Zhongyuan Xu Tao Zhou Changheng Yang
Archives of Civil Engineering | 2022 | vol. 68 | No 1 | 111-128 | DOI: 10.24425/ace.2022.140159
Keywords uniaxial compression parallel cracks numerical simulation mechanical properties failure characteristics
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Abstract

In this study, the uniaxial compression test and the numerical simulation of the twodimensional 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 (��º, crack angle (��1, ��2), and numerical changes in the rock bridge length (ℎ) and bridge angle (��) 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 �� under different �� values. The smaller angle between the preset crack and the loadinging direction (��) resulting in higher UCS. In addition, a larger ℎ results in higher UCS in the specimen. When ��1 or ��2 is fixed, the UCS and elastic modulus of the specimen show an ‘M’ shape with an increase in ��. Moreover, the crack growth or failure mode of samples with different �� values is similar. When ��1 or ��2 is small, the failure of the specimen is affected by the development and expansion of wing cracks. If one of ��1 and ��2 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 ��1 = 0°, the rock bridge is less likely to reach penetration failure as ℎ increases. Secondary crack connections between the prefabricated cracks occur only when �� is small.
When �� ¡ 30°, the failure mode of the specimen is crack tip cracking which leads to penetration failure of the specimen, or the overall splitting failure.
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Authors and Affiliations

Jie Yang
1
ORCID: ORCID
Haijun Chen
2
ORCID: ORCID
Xiong Liangxiao
3 4
ORCID: ORCID
Zhongyuan Xu
5
ORCID: ORCID
Tao Zhou
1
ORCID: ORCID
Changheng Yang
3
ORCID: ORCID
  1. College of Environment and Civil Engineering, Chengdu University of Technology, Chengdu, 610059, PR China
  2. Geotechnical Engineering Department, Nanjing Hydraulic Research Institute, Nanjing, Jiangsu Province, 210029, PR China
  3. School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, PR China
  4. Hunan Provincial Key Laboratory of Hydropower Development Key Technology, HydroChina Zhongnan Engineering Corporation, Changsha 410014, PR China
  5. Department of Earth Sciences, University of Delaware, Delaware 19716, United States

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