Abstract
This paper presents a comprehensive investigation into the stability of a circular tunnel constructed in soil
containing a circular void. To achieve this, an adaptive finite element limit analysis (FELA) approach, combined with
nonlinear programming (NLP), is employed. To enhance the convergence speed of the NLP algorithm, a novel
approach is introduced, incorporating the feasible arc interior point algorithm (FAIPA) to perturb the search direction
through a secondary deflection, and an imprecise step search algorithm to improve the efficiency of step length
search. Based on the FELA method, both the upper bound (UB) and lower bound (LB) of the non-dimensional
stability number are computed. Extensive parametric studies are conducted to evaluate the effects of key parameters
on tunnel stability. The computational results are effectively conveyed through the utilization of dimensionless
stability tables and charts, specifically designed to facilitate ease of use by engineers. Furthermore, meticulous
examination of typical failure mechanisms provides deep insights into the complex behavior of tunnels under varying
conditions.
Key Words
finite element limit analysis; imprecise step search; nonlinear programming; stability; tunnels
Address
Tao Liu, Rui Zhang, Shilin Luo: College of Civil Engineering, Changsha University, 98 Hongshan road, Kaifu district,
Changsha, 410022, PR China
Yao Xiao: College of Civil Engineering and Architecture, Guangxi University, 100 Daxue east road, Xixiangtang district,
Guangxi, 530004, PR China
Tiebiao Liu: Geophysical and Geochemical Survey Institute of Hunan Province, 898 Duan 2, Wanjiali south road,
Tianxi district, Changsha, 410114, PR China
Abstract
Understanding the thermal-hydraulic-mechanical behavior of rock joints is essential in many civil and
rock engineering applications, but controlled testing on natural joints is often impractical. This study investigates
artificial tensile joints generated by wedge-splitting in medium- to coarse-grained granite specimens and evaluates the
effects of loading rate, specimen size, and loading direction on surface morphology. Block and cylindrical specimens
were tested under loading rates of 0.0001~0.01 mm/s. Joint surfaces were digitized via 3D laser scanning; directional
profiles at 15 increments were used to compute three roughness parameters including CLA (Center Line Average),
Z2 (root mean square of the first derivative of a profile), and fractal dimension (D). Spatial correlation was quantified
using the experimental variogram with spherical fits to obtain range and sill. No discernible rate dependency was
detected in either roughness or variogram parameters within the tested range. Size effects were parameter-specific:
CLA increased with specimen size, whereas Z2 and D were relatively higher in the smallest specimens. Roughness
showed a clear directional effect, being greater perpendicular to the loading axis than parallel. Variogram parameters
increased with size (both range and sill), while directional differences in spatial correlation were weak and generally
not statistically significant. Consistent with the amplitude-correlation relationship, the sill related to CLA, and a
normalized initial slope (sill range) qualitatively related to Z2 and D. Overall, specimen size and loading
direction govern the scale of roughness that is emphasized, providing practical guidance for the design and
interpretation of experiments using artificial joint specimens.
Key Words
artificial rock joint; directionality; loading rate; morphological characteristics; specimen size;
splitting test
Address
Seungbeom Choi, Taehyun Kim, Seong Jun Ha, Saeha Kwon, Jin-Seop Kim: Korea Atomic Energy Research Institute, 111, Daedeok-daero 999 beon-gil, Yuseong-gu,
Deajeon, 34057, Republic of Korea
Abstract
This study evaluates the lateral capacity of flexible pre-bored precast concrete (PC) piles under drained
soil conditions by employing various representative interpretation criteria. A database comprising 15 field lateral load
tests in Taiwan was analyzed to investigate the relationships and reliability among various displacement, rotation, and
graphical-based interpretation methods. Results show that the mean interpreted Q/QH ratios for displacement and
rotation-based methods range from 0.20 to 0.80, increasing with larger movements. For graphical methods, the ratios
are QS&W/QH = 0.42 and QL/QH = 0.59, with standard deviations and coefficients of variation comparable to other
criteria. The QL method provided the most reasonable and consistent evaluation of both capacity and displacement,
corresponding closely to the load at 20 mm or 3% of the pile diameter. Regression analysis identified Q10%B as the
most reliable predictor, with a high coefficient of determination (r2 = 0.92). Overall, pre-bored PC piles exhibited
higher normalized lateral capacities than drilled shafts and driven piles. The findings provide practical guidance for
the consistent interpretation and design of flexible pre-bored PC piles under lateral loading.
Key Words
database; interpretation criteria; lateral capacity; load tests; pre-bored PC piles
Address
Xing-Ji Wang, Yit-Jin Chen, Mary Abigail Jos: Department of Civil Engineering, Chung Yuan Christian University, Chung-Li, Taiwan
Anjerick Topacio: Department of Civil, Industrial, and Mechanical Engineering, Lyceum of the Philippines University – Cavite,
Cavite, Philippines
Abstract
As a tunnel boring machine (TBM) manufacturer, the serious challenge of designing the machine is the
most crucial part. However, as a TBM operator, the most crucial challenge is selecting a proper TBM based on the
ground conditions. The disc cutter is an effective factor involved in the functionality of TBMs. Proper disc cutter
design can greatly reduce the concerns of manufacturers and operators. An appropriate design can be attained
through a precise evaluation of the disc cutter life (DCL) under varying operating conditions. In this work, the
Xtreme Gradient Boosting (XGBoost) method was used to evaluate the TBM‒DCL. 200 datasets, including nine
effective parameters were utilized in the model (80% for training and 20% for testing). The performance ability of the
XGBoost method was increased through tuning its hyper‒parameters using several meta‒heuristic optimization
algorithms. All the hybrid models showed potential ability in the TBM‒DCL prediction. However, the XGBoost‒
particle swarm optimization model was the most robust one. Sensitivity analysis revealed that the cutter rotation
speed had the greatest impact on the model's output. This work's significance is that it can address many of the
manufacturer and operator concerns about TBM design and use in different ground conditions.
Address
Shtwai Alsubai, Abdullah Alqahtani,Abed Alanazi: Department of Computer Science, College of Computer Engineering and Sciences in Al-Kharj,
Prince Sattam bin Abdulaziz University, P.O. Box 151, Al-Kharj 11942, Saudi Arabia
Taoufik Saidani: Center for Scientific Research and Entrepreneurship, Northern Border University, Arar 73213, Saudi Arabia
Arsalan Mahmoodzadeh: Center of Research and Strategic Studies, Lebanese French University, Erbil, Iraq
Mohamed Ghalla: Faculty of Engineering & Digital Technologies, University of Bradford, Bradford BD71DP, UK
Abstract
Dredging activities associated with waterway and infrastructure construction generate large volumes of
high-water-content dredged clay, whose poor sedimentation and dewatering characteristics pose significant
challenges for earth structures and ground engineering applications. An improved understanding of the sedimentation
behavior of such geomaterials under flocculant treatment is therefore essential for effective reuse and engineering
design. In this study, a systematic experimental investigation was conducted to examine the effects of flocculant type,
dosage, and initial water content on the sedimentation behavior of dredged clay. Sedimentation column tests were
performed on clay suspensions treated with four representative flocculants, including superabsorbent polymer (SAP),
polyacrylamide (PAM), polyaluminum chloride (PAC), and calcium hydroxide [Ca(OH)2], over a wide range of
dosages and initial water contents. Settlement evolution, sedimentation rate, and post-sedimentation water content
distribution were quantitatively analyzed. The results indicate that flocculant treatment markedly accelerates
sedimentation and increases final settlement compared with untreated clay. For all flocculants, both settlement and
peak sedimentation rate exhibit a non-monotonic dependence on dosage, with an initial increase followed by a
reduction at higher dosages, indicating the existence of an optimal dosage range. Among the flocculants investigated,
SAP demonstrates the most pronounced enhancement of sedimentation performance, particularly at higher initial
water contents, owing to its strong water-absorption capacity and effective particle aggregation. The optimal SAP
dosage increases with increasing initial water content, highlighting the coupled influence of slurry state and flocculant
content. In addition, post-sedimentation water content shows clear vertical stratification within the slurry cake,
reflecting differences in particle size distribution and drainage conditions during settling. The experimental findings
provide quantitative insight into the sedimentation mechanisms of flocculant-treated dredged clay and offer practical
guidance for the selection and optimization of flocculants in earthwork, ground improvement, and dredged material
reuse applications.
Key Words
dredged clay; flocculant; sedimentation rate; settlement; water content
Address
Yupeng Cao: College of Civil and Transportation Engineering, Weifang University, Weifang, 261061, China;
Shandong Key Laboratory of Intelligent Manufacturing Technology for Advanced Power Equipment,
Weifang, 261061, China
Yan Xu: School of Modern Agriculture and Life Sciences, Weifang University, Weifang, 261061, China
Xiang Yong: School of Civil Engineering, Shenyang Jianzhu University, Shenyang, 110168, China
Nuo Xu, Jie Yin: Department of Civil Engineering, Faculty of Civil Engineering and Mechanics, Jiangsu University,
Zhenjiang, 212013, China
Naibin Sun: Shandong Provincial Road and Bridge Group Co., Ltd., Jinan, 251400, China
Abstract
DEM (Discrete Element Method) simulates geotechnical materials such as sand using a particle-based
approach. SPH (Smoothed Particle Hydrodynamics) is also a mesh-free method for simulating fluids. In this study a
coupled DEM-SPH model was developed to simulate the undrained behavior of saturated geotechnical materials
such as saturated sand. The solid phase was simulated using DEM and the fluid phase was simulated using SPH. The
both methods were coupled by applying interaction forces to the fluid and solid phases. The presented DEM-SPH
model resolved the need for a spatial mesh. The model was validated by comparing its results to existing
experimental data. The undrained triaxial shear test was simulated to show the capabilities of the numerical model.
Using the developed DEM-SPH model the fluid pressure and velocity distributions were studied at several axial
strains. The fluid velocity in upper parts of the sample has similar magnitude to the loading velocity with
approximately vertical direction. In the lower parts the fluid velocity was close to zero with different directions. Three
stages of pressure distribution were recognized; (i) transient stage related to wave propagation, (ii) stable stage related
to elastic deformations of the sample, and (iii) instable stage related to particle sliding. The results showed that the
numerical model can satisfactory predict the response of the granular material to undrained loading and accurately
simulate the distribution of the inter-particle fluid local parameters.
Key Words
DEM; geotechnical simulation; mesh-free; saturated sand; SPH
Address
Younes Khalili, Ahmad Mahboubi∗, Mohammd Haji-Sotoudeh: Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran
open access