Abstract
This study aims to quantitatively elucidate the mechanisms by which principal stress axis orientation
controls the mechanical behavior of rock, focusing on both macroscopic mechanical behavior and microscopic
failure processes. Three types of complex stress-path tests were conducted on hollow-cylinder gray sandstone
specimens using PFC3D. The study identifies that crack growth is governed by the principal stress orientation under
low axial stress, while non-coaxial deformation dominates under high axial stress, leading to reduced influence of
stress orientation and more complex fracture patterns. Based on acoustic emission monitoring data obtained from the
numerical simulations, two novel indices, namely damage efficiency (DE) and non-coaxial damage index (NCDI),
are proposed. These indices quantitatively characterize the coupling effect between stress axis rotation and damage
accumulation in rock. These findings provide deeper insight into the failure mechanisms of rocks under nonconventional
stress paths and support improved design and risk assessment in geotechnical engineering.
Key Words
discrete element method (pfc3d); hollow cylindrical gray sandstone; mechanical response;
principal stress axes rotation; stress path
Address
Liang Fang, Wendong Zou: School of Civil Engineering, Suzhou University of Science and Technology, Suzhou, Jiangsu 215099, China
Yue Jiang: School of Civil Engineering, Suzhou University of Science and Technology, Suzhou, Jiangsu 215099, China;
State Key Laboratory of Geomechanics and Geotechnical Engineering Safety, Institute of Rock and Soil
Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
ingjing Lu, Yang Gao, Feifei Jiang: State Key Laboratory of Geomechanics and Geotechnical Engineering Safety, Institute of Rock and Soil
Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
Abstract
Utilizing waste materials as soil replacements offers a sustainable path for geotechnical engineering. This
study explores sugarcane bagasse, an abundant agricultural waste as a partial soil replacement, focusing on its
dynamic characteristics. While previous studies examined static behavior with small reinforcement percentages,
dynamic characterization with partial sand replacement remains unexplored. This research fills that gap using straincontrolled
cyclic triaxial and bender element tests on six mixes, with bagasse content from 0% to 50% by volume
(BS0 to BS50). The effects of confining pressure, relative density, and strain amplitude (0.3%–3%) were studied,
focusing on maximum shear modulus, shear modulus, and damping ratio. Bagasse-sand mixes restricted cyclic loads
via interparticle networks. Increased bagasse content reduced shear modulus but enhanced the damping ratio. Stressstrain
curves showed stiffness degradation, with BS0 displaying larger hysteresis loops. Excess pore pressure and
strain contributed to this reduction. Shear wave velocity and maximum shear modulus declined with more bagasse,
BS0 had the highest (98.7 MPa), BS50 the lowest (7.25 MPa). Mixes up to 30% bagasse retained a relatively sanddominated
response, while higher contents showed bagasse dominated behavior. Overall, these mixes offer ecofriendly,
vibration-reducing solutions and promote sustainable waste management, when optimally mixed.
Address
Jithin P. Zachariah: Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India
Jithin P. Zachariah, Ravi S Jakka: Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India;
International Centre of Excellence for Dams (ICED), Indian Institute of Technology Roorkee, Roorkee, India
Abstract
Sandstone widely occurs within the hydro-fluctuation belts of reservoir banks and is susceptible to
progressive deterioration under repeated wetting-drying cycles, posing potential risks to long-term slope stability. To
investigate this process, moderately weathered sandstone collected from a landslide hydro-fluctuation belt in the
Three Gorges Reservoir area was subjected to 0-20 wetting-drying cycles. Uniaxial and conventional triaxial
compression tests were conducted in combination with nuclear magnetic resonance (NMR) and scanning electron
microscopy (SEM) to characterize the mechanical degradation and mesoscopic structural evolution of the rock. In
addition, a two-dimensional numerical damage model incorporating mesoscopic heterogeneity was established based
on continuum damage mechanics and the Weibull statistical distribution. The results show that wetting-drying cycles
significantly reduce the peak strength, elastic modulus, cohesion, and internal friction angle of sandstone, exhibiting a
clear nonlinear degradation trend. Meanwhile, the failure mode gradually evolves from shear-dominated brittle
failure to a more ductile pattern characterized by multi-crack interaction. At the microscale, water-rock interaction
and cement dissolution promote micropore development and connectivity, increasing intermediate pore volume and
weakening the load-bearing skeleton of the rock. Numerical simulations reproduce the progressive evolution of
microcracks into macroscopic conjugate fracture networks, providing a reliable basis for evaluating reservoir bank
slope stability under cyclic wetting-drying conditions.
Key Words
damage mechanism; deformation and failure; strength characteristics; water-rock interaction;
wetting drying cycles
Address
Heng Zhang, Shu Zhu, Liuming Chang, Zhicheng Wang, Jin Zhang,
Xiangcheng Que: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,
Hohai University, Nanjing 210098, China;
School of Civil Engineering and Transportation, Hohai University, Nanjing 210098, China
Feiyang Wang: Department of Civil Engineering, College of Environmental Science and Engineering,
Donghua University, Shanghai 201620, China
Zhende Zhu: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,
Hohai University, Nanjing 210098, China;
School of Civil Engineering and Transportation, Hohai University, Nanjing 210098, China;
College of Hydraulic and Civil Engineering, Xinjiang Agricultural University, Urumqi 830052, China
Abstract
The soil-cement grout interfaces are commonly involved in a wide range of civil engineering, and their
strength significantly influences the stability of the whole structure. This paper investigates the strength of the
interface between unsaturated soil and cement grout. A series of direct shear experiments are conducted on the
interface under different initial water contents. Based on the test results, the strength equation expressed in terms of
the degree of saturation was proposed. The proposed expression does not include suction, thereby avoiding the need
for its measurement or control. Furthermore, a constitutive model for the soil-grout interface is then established
within the framework of the disturbed state concept. The critical state strength equation is adopted to represent the
fully adjusted state, while an elastic model is taken as the relatively complete state. The shear modulus related to the
degree of saturation is used in the elastic model. The model has a total of 8 parameters, including 4 strength
parameters, 2 elastic modulus parameters, and 2 disturbance parameters. All these parameters can be predicted by
direct shear tests. The model is validated against experimental data, and the corresponding model parameters are
analyzed accordingly. Results show that the proposed model can satisfactorily reproduce the interface behavior. The
proposed model requires only conventional direct shear tests, effectively simplifying experimental and computational
procedures and shortening test duration.
Key Words
cement grout; degree of saturation; interface; strength model; unsaturated soil
Address
Yan Liu and Ye Feng: Key Laboratory of Urban Underground Engineering of Ministry of Education,
Beijing Jiaotong University, Beijing 100044, China
Yuxin Zhao: Key Laboratory of Urban Underground Engineering of Ministry of Education,
Beijing Jiaotong University, Beijing 100044, China;
Institute of urban systems engineering, Beijing academy of science and technology, Beijing 100089, China
Wen Zhang: Key Laboratory of Urban Underground Engineering of Ministry of Education,
Beijing Jiaotong University, Beijing 100044, China;
Hohhot Electric Power Survey and Design Institute, Hohhot Power Supply Company, Hohhot,
Inner Mongolia, 010090, China
Abstract
Soil improvement techniques are widely used in deep excavation projects near metro stations; however,
there remains a lack of reliable guidance for determining the parameters of the Hardening Soil model with smallstrain
stiffness (HSS model) for cement-stabilized soils. Laboratory tests on cement-stabilized soils from the
Shanghai West Station project were performed at curing ages of 3, 7, 14, and 28 days to determine the corresponding
HSS model parameters. By comparing these results with the parameters of in-situ soil, the strength development and
interrelationships among the parameters at different curing ages were analyzed, leading to the establishment of an
HSS parameter determination method based on curing-age evolution. Numerical analysis of an engineering case
shows that the calculated horizontal deformation of the retaining wall agrees well with the measured values,
validating the applicability of the proposed parameter determination method for excavations involving cementstabilized
soils; furthermore, the effects of curing age and related parameters on excavation behavior are analyzed to
provide references for engineering design.
Key Words
cement-stabilized soil; consolidation test; HSS model; resonant column test; triaxial test
Address
Jian Hua, Fayun Liang, Hanbo Zheng: 1Department of Geotechnical Engineering, Tongji University, 1239 Siping Road, Yangpu District,
Shanghai, P.R. China
Lin Li: School of Highway, Chang
Abstract
Controlling leakage and infiltration in subsurface is critical for maintaining underground structural
stability and mitigating environmental impacts. Conventional cement-based grouts have high CO2 emissions and the
potential for internal discontinuities. This study investigated the applicability of biopolymer-based grout systems,
including xanthan gum grout, agar gum grout, gelatin grout, and gelatin–tannic acid grout, as sustainable alternatives
to conventional cement grout. Scaled geotechnical models featuring various structures, including H-core, Double Hcore,
Secant-Construction in Place (CIP), and Trapezoid-core, were subjected to high-pressure (up to 500 kPa)
permeability tests to assess their impermeability and injection performance. The pre-treatment hydraulic conductivity
ranged from approximately 10-8 to 10-5 cm/s, whereas post-treatment values after 1–7 days of curing decreased to
approximately 10-9–10-6 cm/s for most biopolymer-treated specimens. Among the tested materials, gelatin–tannic
acid grout showed the most pronounced short-term permeability reduction due to crosslinking-enhanced gel
formation. In particular, crosslinked gelatin with tannic acid produced robust gel networks, ensuring favorable
impermeability under high-pressure conditions. Injectability tests showed that agar gum exhibited higher initial
injection volumes due to its low viscosity, while smaller amounts of xanthan gum achieved comparable permeability
reductions, underscoring economic and environmental advantages. By contrast, although cement grout offers a low
unit material cost, its large-scale use significantly increases CO2 emissions and can re-initiate leakage pathways
through internal discontinuities during prolonged high-pressure injection. Overall, these findings demonstrate the
potential of biopolymer-based grouts for short-term permeability reduction in scaled geotechnical structures.
However, long-term durability, biodegradation resistance, cyclic hydraulic loading, and field-scale validation should
be further investigated before practical implementation.
Key Words
biopolymer; cement grout; geotechnical structures; impermeability performance; scaled model
test
Address
Jae-Eun Ryou, Daewon Lee,Seokgu Gang, Jongwon Jung: School of Civil Engineering, Chungbuk National University, Cheongju-si, Chungbuk 28644, South Korea
Jiwoo Lee: Department of Chemical and Biomolecular Engineering,
Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
Shin-in Han: R&D Center, Gaurian Co., Ltd., Goyang-si, Gyeonggi-do 10401, South Korea
Sheng C. Dai: School of Civil & Environmental Engineering, Georgia Institute of Technology, Atlanta,
GA 30332, United States
Nhat-Duc Hoang: Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang 550000, Vietnam;
Faculty of Civil Engineering, Duy Tan University, Da Nang 550000, Vietnam
