Abstract
In underground structures, rock joints are frequently subjected to dynamic impact loading from sources
such as blasting, earthquakes, and mechanical vibrations. Despite the well-established loading-rate dependency of
rock mechanical properties, experimental characterization of joint shear behavior remains limited, particularly in the
intermediate loading-rate (ILR) range. Since the shear behavior of rock joints is significantly influenced by surface
geometry, characterization based solely on planar joint conditions is insufficient for a comprehensive understanding
of joint shear behavior under dynamic loading. In this study, joint shear tests were conducted under ILR conditions
using a Long-Bar Drop Impact (LBDI) apparatus combined with a Compact CNS shear box. Shear tests were
performed under varying initial normal stress conditions on planar joint specimens of three rock types (granite,
gneiss, and limestone) to examine loading-rate dependency, and on artificially generated rough joint specimens with
joint roughness coefficients (JRC) of 4, 12, and 17 to examine the effect of surface geometry. Digital Image
Correlation (DIC) analysis was additionally performed on the rough joint specimens to examine deformation
characteristics associated with rough surface geometry under the CNS boundary condition and to verify the reliability
of displacement measurements. For planar joint specimens, the peak joint shear stress under ILR conditions was
substantially higher than that under quasi-static loading, and the basic friction angle derived under ILR conditions
was notably higher than the quasi-static counterpart. For rough joint specimens, the peak joint shear stress increased
with increasing JRC and initial normal stress, and was substantially higher than the corresponding quasi-static values.
However, no clear dependence on impact velocity was observed within the tested ILR range for either specimen
type. The experimental results for rough joint specimens showed strong agreement with the existing empirical shear
strength model under ILR conditions. The findings suggest that the LBDI apparatus combined with the Compact
CNS shear box provides a reliable and effective platform for investigating joint shear behavior in the ILR regime.
Key Words
basic friction angle; compact CNS shear box; digital image correlation; intermediate loadingrate;
joint roughness coefficient; joint shear test; long-bar drop impact apparatus
Address
Gyeongjo Min: Faculty of Engineering, Hokkaido University, Sapporo, Japan
Hanlim Kim: Department of Mineral Resources & Energy Engineering, Jeonbuk National University, Jeonju, South Korea
Gyeonggyu Kim: Department of Energy Storage and Conversion Engineering, Jeonbuk National University,
Jeonju, South Korea
Jaejun Yang, YongEon Kim: Hanwha Aerospace, Seongnam, South Korea
Sangho Cho: Department of Mineral Resources & Energy Engineering, Jeonbuk National University, Jeonju, South Korea;
Department of Energy Storage and Conversion Engineering, Jeonbuk National University,
Jeonju, South Korea
Abstract
This study combines scaled physical modelling and numerical simulation to investigate the mechanical
behaviour of surrounding rock when tunnels intersect fault zones. Six physical model tests were performed to
compare three tunnel cross-sections, namely circular, horseshoe-shaped, and extended sections, under homogeneous
strata and fault fracture zone conditions. The results show that both radial stress change and displacement develop in
three stages during excavation, namely gradual variation, rapid change, and final stabilisation. Among the three crosssections,
the extended section causes the strongest stress redistribution and deformation, the horseshoe-shaped section
produces an intermediate response, and the circular section produces the weakest disturbance. Compared with
homogeneous strata, excavation in fault fracture zones produces a much stronger surrounding-rock response, with
radial stress-change magnitudes about 1.8–3.0 times higher and displacement increments about 10–20% larger.
Numerical results further indicate that fault-zone thickness and dip angle strongly influence both the scale and spatial
pattern of deformation. A thicker fault zone deepens and widens the longitudinal deformation trough and enlarges the
disturbed range, whereas a larger dip angle produces steeper displacement gradients, stronger asymmetry, and more
localised instability near fault-zone boundaries. These results provide useful guidance for tunnel-section selection and
reinforcement design in complex geological environments.
Address
Yu Zeng, Xi-Lin Lu: Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University,
Shanghai 200092, China
Ping Xu, Hui Dong: College of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China
Xian-Lin Liu: Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;
Guangxi Communications Design Group Co., Ltd., Nanning 530029, China
Yu Shao: Guangxi Communications Design Group Co., Ltd., Nanning 530029, China
Da-Bian Yu: Guangxi New Development Transportation Group Co., Ltd., Nanning 530029, China
Abstract
Skirted footings are nowadays considered one of the best alternatives to deep foundations for both
offshore and onshore structures due to their cost effectiveness. Footing interference is an inevitable phenomenon due
to either scarcity of land or heavy superstructure loads. Most of the previous studies on skirted footings are conducted
for single footing. Very limited studies are conducted on the interference effect of closely spaced skirted footings.
Thus, in the present paper, the effects of structural skirts on bearing capacity improvement and footing interference of
two closely spaced square footings in sand are studied. Small-scale laboratory experiments are conducted under
vertical loadings. Three different skirt depths such as 0.5, 1.0 and 1.5 times the width of the footing are selected for
the study. The interference effects of the skirted footings are compared with the unskirted surface and embedded
footings. In addition to the footing interference of the skirted foundations, the effects of skirt depth and aspect ratio
(length to width ratio) of the footings on bearing capacity improvement are also studied. Three aspect ratios such as
1.0, 1.5 and 2.0 are considered. Significant improvement both in bearing capacity (up to 3.85 times) and settlement
(up to 89% reduction) are observed due to inclusion of the skirts with the footings. The bearing capacity
improvement factor increases due to the increase in skirt depth while the same decreases when the aspect ratio of the
footings is increased. However, the effect of footing interference decreases as the depth of the skirt increases. The
footing interference effect for the skirted footings is less as compared to the conventional unskirted surface and
embedded footings of identical size. Post-test observation showed that the deformation profile of the sand surface in
between the footings is different for the interfering skirted footings as compared to the conventional closely spaced
unskirted surface footings.
Address
Subinay Saha Roy: Faculty of Technology, Uttar Banga Krishi Viswavidyalaya, Cooch Behar, West Bengal, India, 736165
Kousik Deb: Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur, India, 721302
Abstract
Interface roughness governs the cyclic response of soil–rock mixture–concrete contacts, yet its effects on
shear-band development and energy dissipation remain insufficiently resolved. Here, large-scale cyclic direct-shear
tests and discrete-element method simulations were combined to quantify the influence of concrete-surface
roughness on soil–rock mixture–structure interfaces. Three Joint Roughness Coefficient levels (JRC = 0.4, 9.5, and
16.7) were examined at a normal stress of 200 kPa, a stone content of 50%, a displacement amplitude of +-6 mm, and
a loading frequency of 0.1 Hz. The interfaces exhibited progressive cyclic shear hardening, and the magnitude of
hardening increased with roughness. After 100 cycles, the cycle-averaged reversal peak shear stresses at JRC = 9.5
and 16.7 were 10.86% and 25.11% higher, respectively, than that at JRC = 0.4. Simulations of the first 10 cycles
showed that increasing roughness intensified shear localization and promoted anisotropic force transmission within
the granular assembly. Greater roughness increased peak resistance but reduced total external dissipated work,
indicating that stronger geometric interlocking limited relative sliding and particle rotation. At JRC = 16.7, 55.2% of
the simulated sliding and rolling dissipation occurred within the localized zone. These results identify interface
roughness as a key control on the coupling between macroscopic cyclic resistance and micromechanical energy
pathways, and provide a basis for designing roughened structural surfaces in soil–rock mixture systems.
Key Words
cyclic direct shear; dem; energy dissipation; force chains; shear band
Address
Jun Yang,Chenbo Gao: School of Mechanics and Engineering Sciences, Shanghai University, Shanghai, 200444, China
Feiyu Li: School of Mechanics and Engineering Sciences, Shanghai University, Shanghai, 200444, China
Institute of Geotechnical Engineering, School of Civil Engineering and Architecture,
East China Jiaotong University, Nanchang, 330013, China
Abstract
This paper presents a centrifuge model study on the uplift performance of large-diameter rock-socketed
drilled shafts. A series of uplift load tests was conducted to examine the effects of rock strength, socket length, and
layered rock stratigraphy on load–displacement response, axial load transfer, mobilized unit side resistance, and t–z
behavior. The load–displacement was characterized by an initial near-linear region followed by nonlinear transition
and peak resistance. Shafts socketed in weaker rock (2-7 MPa) exhibited plunging-type failure, whereas those
socketed in stronger rock (35 MPa) showed a more brittle post-peak response. Axial load transfer occurred
predominantly within the rock socket, with negligible transfer in the overlying sand layer for partial socket cases. In
layered rock sockets, load transfer was mobilized along the entire shaft length and was affected by both layer strength
and thickness. The mobilized unit side resistance was non-uniform with depth, with peak values generally occurring
in the upper to middle portion of the socket and lower values near the shaft tip. Normalized t–z curves showed that
the displacement required to mobilize maximum unit side resistance decreased with increasing rock strength. Based
on the test results, empirical factors for estimating ultimate side resistance and adhesion factor were derived for largediameter
shafts with smooth socket sidewalls under uplift loading.
Key Words
centrifuge modeling; large-diameter rock-socketed drilled shaft; load transfer; side resistance;
t-z curve; uplift behavior
Address
Sunji Park: Marine Consulting, Fugro, Level 1, 1060 Hay Street, West Perth, 6005, Australia
Seokjung Kim: Department of Civil Engineering, Mokpo National University, 1666 Yeongsan-ro, Muan-gun,
Jeollanam-do 58554, Republic of Korea
Young-Jin Jeon: Institute of Industrial Technology, Kangwon National University, 1 Kangwondaehak-gil,
Chuncheon-si, Gangwon state 24341, Republic of Korea
Jae-Hyun Kim: Department of Civil Engineering, Kangwon National University, 1 Kangwondaehak-gil,
Chuncheon-si, Gangwon state 24341, Republic of Korea
Abstract
Wave-induced seabed scouring critically threatens coastal structures and has become a core issue in
coastal engineering. This study identifies sliding instability as the predominant sediment failure mode under wave
action. Key findings include: (1) wave-generated seepage force significantly reduces the critical shear stress for
sediment incipient motion; (2) maximum bed surface shear stress decreases continuously with increasing water
depth; (3) seabed liquefaction depth exhibits a non-monotonic (increase then decrease) response to rising particle size
and varying seepage directions, peaking under vertically upward seepage; (4) liquefaction depth increases with larger
wave heights and periods but decreases with greater water depth. Sensitivity analysis ranks influencing factors as:
wave height > water depth > wave period > seepage direction > particle diameter, with wave height exerting the
strongest control on scouring evolution. Based on these results, a complete calculation system for the wave friction
coefficient across all flow regimes and a quantitative method for critical scouring depth are established. This work
reveals the intrinsic mechanical mechanisms of wave-induced erosion and provides a robust theoretical basis for antiscouring
design. Practical guidance for coastal management includes prioritizing control of wave-height loads and
optimizing water depth layouts, while tailoring protection measures according to factor sensitivity rankings to
mitigate beach erosion and sustain coastal ecosystem stability.
Key Words
incipient sediment motion; liquefaction depth of seabed; parameter sensitivity analysis; seabed
scouring; wave action
Address
Jing Wu, Wangli Xing, Lei Guo,Lewen Zhang, Minghong Sun: Institute of Marine Science and Technology, Shandong University, Qingdao, Shandong, 266237, China;
Shandong Key Laboratory of Intelligent Marine Engineering Geology, Environment and Equipment,
Qingdao, Shandong, 266237, China
Huayi Liu: School of software, Shandong University, Jinan, Shandong, 250101, China
open access