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CONTENTS
Volume 39, Number 2, October25 2024
 

Abstract
Biopolymer treatment of geomaterials is a promising technology with green technology potential that can help reduce global warming. It offers a positive environmental impact and a wide range of applications. This paper reports the results of a study of the mechanical performance of biopolymer-treated dune-sand from the Algeria desert. The sand was mixed with varying amounts of xanthan gum biopolymer and reinforced with polypropylene fibre. The study demonstrated that xanthan gum treatment improved the Unconfined Compressive Strength (UCS) of unreinforced sand and fibre-reinforced sand. Nonetheless, the test results revealed that biopolymer-treated sand manifested higher resistance after drying. Based on the findings, the optimal quantity of xanthan gum for treating sand is 2%. The incorporation of fibre in the matrix increases the strength and failure strain. The Scanning Electron Microscopy (SEM) analysis further substantiated that the biopolymer bonds the sand particles together and the distribution of PP fibre in the mixture, thereby enhancing compressive strength and durability. The results indicate that using xanthan gum biopolymer treatment offers an environmentally friendly approach to enhancing the mechanical properties of desert sand.

Key Words
biopolymer; compressive strength; desert sand; polypropylene fibre; SEM test; Xanthan gum

Address
Benathmane Baghdir and Younes Abed: NEIGE Laboratory, Civil Engineering Department, Saad Dahleb university, BP 270 Road Soumâa –BLIDA, Algeria
Sadok Feia: Research Laboratory of Civil Engineering, Civil Engineering Department, Biskra University, 07000, Biskra, Algeria
Sidali Denine: Civil Engineering Department, Center University of Tipaza, Tipaza, Algeria
Turgay Beyaz: Department of Geological Engineering, School of Engineering, Pamukkale University, Denizli, Türkiye
Achref Cherifi: Industrial Technology Research Center, Additive Manufacturing Research Unit, Industrial Zone A15. Setif 19000, Algeria


Abstract
The most significant soil parameters that are utilized in geotechnical engineering projects'design and implementations are soil strength parameters including friction (o), cohesion (c), and uniaxial compressive strength (UCS). Understanding soil shear strength parameters can be guaranteed the design success and stability of structures. In this regard, professionals always looking for ways to get more accurate estimations. The presented study attempted to investigate soil shear strength parameters by using multivariate regression and multilayer perceptron predictive models which were implemented on 100 specimens'data collected from the Tabriz region (NW of Iran). The uniaxial (UCS), liquid limit (LL), plasticity index (PI), density (v), percentage of fine-grains (pass #200), and sand (pass #4) which are used as input parameters of analysis and shear strength parameters predictions. A confusion matrix was used to validate the testing and training data which is controlled by the coefficient of determination (R2), mean absolute (MAE), mean squared (MSE), and root mean square (RMSE) errors. The results of this study indicated that MLP is able to predict the soil shear strength parameters with an accuracy of about 93.00% and precision of about 93.5%. In the meantime, the estimated error rate is MAE = 2.0231, MSE = 2.0131, and RMSE = 2.2030. Additionally, R2 is evaluated for predicted and measured values correlation for friction angle, cohesion, and UCS are 0.914, 0.975, and 0.964 in the training dataset which is considerable.

Key Words
geotechnical engineering; multivariate regression; shear strength; soil materials

Address
Ahmed Cemiloglu: School of Information Engineering, Yancheng Teachers University, Yancheng 224002, Jiangsu, China

Abstract
Traffic-induced cyclic loading leads to the rotation of principal stresses within pavement foundations, challenging accurate simulation with conventional triaxial testing equipment. To investigate the deformation characteristics of fiber-reinforced soil under traffic loads and to develop a fractional-order model to describe these deformations. A series of hollow cylinder torsional shear tests were conducted using the GDS-SSHCA apparatus. The effects of fiber content, load frequency, cyclic deviatoric stress amplitude, and cyclic shear stress amplitude on soil deformation were analyzed. The results revealed that fiber content up to 3% enhances soil resistance to deformation, while higher fiber content reduces it. Axial cumulative plastic deformation decreases with higher load frequencies and increases with higher cyclic stresses. The study also found that principal stress rotation exacerbates soil deformation. A fractional integral model based on the Riemann-Liouville operator was developed to describe the axial cumulative plastic strain, with its validity confirmed by supplementary tests. This model provides a scientific basis for understanding foundation deformation under traffic loading and contributes to the development of dynamic constitutive soil models.

Key Words
axial cumulative plastic strain; cyclic torsional shear test; fiber-reinforced soil; RL fractional integra operator; soil mechanics

Address
Jiashun Liu: School of Civil Engineering, Liaoning Technical University, Fuxin 123000, P. R. China;
Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing, 210009, P. R. China;
Kaixin Zhu: School of Civil Engineering, Chongqing University, No.83 Shabei Street, Shapingba District, Chongqing, 400045, P. R. China;
School of Civil Engineering, Liaoning Technical University, Fuxin 123000, P. R. China
School of Mechanics and Civil Engineering, China University of Mining & Technology-Beijing, P. R. China
Yanyan Cai: Tunnel and urban underground space engineering technology research center, Huaqiao University, Xiamen 361021, P. R. China
Shuai Pang: School of Civil Engineering, Liaoning Technical University, Fuxin 123000, P. R. China;
College of Water Resources and Architectural Engineering, Northwest A&F University, 23# Wei-hui Road,
Yangling City, Shaanxi 712100, P. R. China
Yantao Sheng: School of Civil Engineering, Liaoning Technical University, Fuxin 123000, P. R. China

Abstract
In the present study, the acoustic emission characteristics of hard sedimentary sandstone with varying bedding dip angles were examined through uniaxial compression tests using a rock mechanics creep apparatus combined with an acoustic emission system. The deformation and failure behavior of the sandstone was analyzed by correlating acoustic emission parameters with stress over time. A damage constitutive model was developed, incorporating cumulative acoustic emission ringing counts as a key parameter, with time acting as the intermediary. The findings indicate that, despite the differences in bedding dip angles, the stress-strain curves of the samples follow a similar pattern throughout the loading process, passing through four distinct phases: compaction, elastic deformation, yielding, and post-peak failure. The fracture patterns of the sandstone are influenced by the dip angle of the bedding. Acoustic emission parameters, including the ringing count, cumulative ringing count, and energy, align with these four stages of the stress-strain curve. During the compaction and elastic deformation phases, acoustic emissions remain in a quite state, with only brief spikes at points of rapid stress change. In the unstable fracture stage, acoustic emissions become highly active, while they return to a quite state in the post-fracture stage. The RA value of the acoustic emission displays a banded pattern as time progresses, with areas of dense clustering. When the stress curve declines, RA values enter an active period, mainly associated with the generation of shear cracks. Conversely, during periods of smooth stress progression, RA values remain in a quiet state, primarily linked to the formation of tensile cracks. The time-based damage constitutive model for layered sandstone effectively captures the entire process of rock fracture development.

Key Words
acoustic emission; bedding inclination; constitutive model; layered sandstone; rupture response

Address
Zhanping Song and Xiaoxu Tian: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China;
Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering, Xi'an 710055, China;
Institute of Tunnel and Underground Structure Engineering, Xi'an 710055, China
Xiaojing Xu: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China;
Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering, Xi'an 710055, China
Tong Wang: Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering, Xi;an 710055, China;
School of Civil Engineering, Xi'an Shiyou University, Xi'an 710065, China
Wanxue Song: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
Yun Cheng: Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering, Xi'an 710055, China
College of Civil Engineering, Yancheng Institute of Technology, Yancheng 224051, China


Abstract
Gravity wall combined with anchoring frame beam is widely adopted to support a high slope under complex geomorphic condition, in which the rigid gravity wall is adopted as a lower structure and the flexible anchoring frame beam serves as an upper structure. The seismic anchor force and the seismic active earth pressure are two essential issues for the seismic design of combined retaining structure in high seismic intensity area. In this study, an analytical model of combined retaining structure is established based on the upper bound theorem of limit analysis, and the formulas for seismic anchor force and seismic active earth pressure of combined retaining structure are derived. The results are optimized by using the global optimization algorithm. The proposed method is verified by a comparison with previous method. Moreover, the influence of main parameters on seismic anchor force and seismic active earth pressure is analyzed to facilitate the seismic design of such combined retaining structure.

Key Words
anchoring frame beam; gravity wall; seismic active earth pressure; seismic anchor force; upper bound theorem

Address
Yu-liang Lin and Li Lu: School of Civil Engineering, Central South University, Changsha 410075, China;
Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering Structures of Hunan Province,
Central South University, Changsha 410075, China
Hao Xing and Xi Ning: The Fourth Engineering Co., Ltd., China Railway Seventh Group, Wuhan 430074, China
Li-hua Li: Key Laboratory of Health Intelligent Perception and Ecological Restoration of River and Lake, Ministry of Education,
Hubei University of Technology, Wuhan 430068, China

Abstract
Existing piles, especially in urban areas, are at risk of being cut by new tunnel construction, potentially affecting their serviceability. This study examined the behaviour of piles under various reinforcement conditions subject to tip cutting resulting from tunnel excavation. For this, the construction of a tunnel using a shield tunnel boring machine adjacent to existing single and group piles was simulated. A three-dimensional finite element analysis was used to perform the simulations. Certain piles in the group were simulated by cutting the pile tips to mimic the effect of tunnel excavation, and the behaviour of the piles was studied by considering the effect of pile cap and ground reinforcements. A numerical analysis was used to examine the ground settlement caused by tunnel excavation, pile head settlement, axial pile force, and shear stress occurring at the pile–ground interface. The results revealed that for all piles with pile tips supported by weathered rock, the shear stress distributions demonstrated similar trends, whereas for piles with cut tips, tensile or compressive forces occurred simultaneously according to the relative position by pile depth. Additionally, when the pile tip was supported by weathered rock, approximately 70% of the support was due to shaft friction and the remaining 30% was provided by the pile tip. For piles without reinforcement, the final settlement was approximately 70% greater than that of piles with grouting reinforcement. These results indicate that pile and ground settlements are substantially influenced by pile tip cutting and reinforcement conditions.

Key Words
numerical analysis; pile cutting; pile behaviour; reinforcement conditions; shield TBM

Address
Young-Jin Jeon: College Institute of Industrial Technology, Kangwon National University,
1 Kangwondaehak-gil, Chuncheon-si, Gangwon-do, Republic of Korea
Seung-Kueon Seo: Hence Company Limited, 63 gil 45, Poongseong-ro, Gangdog-gu, Seoul, Republic of Korea
Young-Nam Choi: Center for Climate Change Research, Chungnam Institute,
360, Hongye-ro, Hongbuk-eup, Hongseong-gun, Chungcheongnam-do, Republic of Korea
Ho-Yeol Son: Pyeonghwa Dam Office, K-water, 3481-18, Pyeongwa-ro, Hwacheon-eup, Hwacheon-gun, Gangwon-do, Republic of Korea
Byung-Soo Park: Department of Civil Engineering, Gangwon State University,
270 Yeonju-ro, Jumunjin-eup, Gangneung-si, Gangwon-do, Republic of Korea
Jae-Hyun Kim and Cheol-Ju Lee: Department of Civil Engineering, Kangwon National University, 1 Kangwondaehak-gil, Chuncheon-si, Gangwon-do, Republic of Korea

Abstract
This paper investigated the deformation of a large-diameter pipeline caused by double shield tunnel construction in silty fine sand strata in Nantong, China, by on-site measurements and numerical simulations. Results indicate the pipe settlement curve was not symmetrical after the double tunnel construction in the silty fine sand strata. The construction of the subsequent tunnel had a significantly smaller impact on the stress and horizontal displacement of the pipeline than the preceding tunnel. There is a significant shading effect of the large-diameter pipeline, which would restrict the soil settlement above the pipeline. The adjusted settlement formula shows good agreement with the measured data, facilitating approximate calculations for both surface and pipe settlements. The correction factor a ranges from 0.50 to 0.90, while b ranges from 0.95 to 1.20.The elastic modulus and the burial depth of the pipeline had a great effect on the stress of the pipeline, but a smaller effect on its settlement. However, the soil loss rate greatly affected both the settlement and stress of the pipeline. Moreover, the pipeline risk level distribution map can quickly identify the risk status of the pipeline.

Key Words
double shield tunneling; field tests; large-diameter pipeline; numerical simulation; pipeline deformation; silty fine sand strata

Address
Ning Jiao, Jianwen Ding, Xing Wan and Xia Wei: Institute of Geotechnical Engineering, School of Transportation, Southeast University,
No.2, Southeast Road, Jiangning District, Nanjing, 211189, China
Zhaosheng Liao: Direct Affairs Center of the Yiyang Transportation Bureau, Yiyang, 413000, China

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