Abstract
Joint leakage is one of the major defects in river-crossing tunnels during operation period. The influence of leakage
under different joint locations on the tunnel structure is different. In this paper, a combination of model tests and numerical
simulations was developed to investigate the influence of leakage under different joint locations during operation period on the
tunnel structure and the strata. Specifically, the difference of joint permeability coefficients with different locations was
considered, and the formula quantifying the relationship between the permeability coefficient and the angle of joint was
established. Nanjing Dinghuaimen River-Crossing Tunnel in China was used as the engineering background to study the leakage
patterns for different locations of joints. The results show that the tunnel structure responds more to leakage at tunnel arch
bottom and foot during operation period. When leakage occurs at tunnel arch foot, the infiltration volume is 33.6% more than
that at the tunnel vault, and the surface settlements are 2.4 times more than that at the tunnel vault. The surface settlement caused
by the joints is related to the infiltration volume. The location of the joints affects the shape of the lining deformation and the
overall deformation is less. The results of this paper have certain guiding significance for tunnel maintenance projects.
Key Words
joint leakage location; model test; operation period; river-crossing tunnel
Address
Yu Xiang, Bai Shuaiqiang and Wang Yuke: School of Water Conservancy and Transportation, Zhengzhou University, Zhengzhou, China
Chen Can: Henan Hydrology and Water Resources Center, Zhengzhou, China
Xue Yujie: College of Vehicle and Traffic Engineering, Zhengzhou University of Science and Technology, Zhengzhou, China
Abstract
It is a fact that liquefaction, which is defined as the temporary loss of bearing capacity in liquefiable soils, is a major
problem that causes serious loss of life and property during earthquakes. Therefore, in this study the chemical sodium
polyacrylate (SPA) is implemented to decrease the liquefaction potential, and to minimize the harmful effects on soil-structure
interaction as a key improvement method against liquefaction. The extraordinary water absorption capacity of this material and
the sealing property of a trace cement addition are used logically to absorb pore water and increase viscosity by changing the
water's phase into a gel state. In total, twenty-five cases are performed, consisting of a horizontal layer, a vertical barrier and a
complete mixing operation, according to different chemical ratios and application positions. As a result of shaking table tests, a
better effect is obtained when the horizontal layer is placed close to the ground surface, while the optimum content of the
mentioned chemical is found to be around 0.5% by weight in the vertical barrier and complete mixing applications in terms of
excess pore water pressure and settlement values. It has been determined that the most important improvement parameters are
the optimum SPA content and water supply condition, rather than the excessive addition of chemicals to the soil, regardless of
the application type. The settlement potential of base plate was limited due to the counterbalancing of excess pore water pressure
in sandy soil by the swelling pressure of SPA.
Key Words
chemical improvement; ground improvement; liquefaction; pore pressure; settlement; shaking table
Address
Nesil Özbakan, Ömer F. Güler and Burak Evirgen: Department of Civil Engineering, Eskisehir Technical University, 26555, Eskisehir, Türkiye
Abstract
In the hydraulic fracturing process, the mechanical behavior of bedding planes is known to influence the growth of
fractures in the surrounding rock. An analytical investigation was conducted into the growth process of hydraulic fractures in
bedded rock. The effects of the number of bedding layers, the mechanical properties of these layers, internal pressure, and
confining pressure on radial displacement, radial stress, tangential stress, and the critical radii of failure were examined. In all
samples, the bedding planes were oriented perpendicular to the internal pressure. It was observed that as internal pressure
increased, radial stress values rose while tangential stress values decreased. When the internal uniform compressive load
matched the external load, the values of radial and tangential stresses became independent of radial distance in the cylindrical
specimen. It was found that hydraulic fractures (HF) may propagate within the bedding layers due to a decrease in the modulus
of elasticity and strength of the rock. Shear failure in the hydraulic fractures was found to be exacerbated when cohesion and
friction angle values were low. Numerical simulations indicate that four major sets of tensile fractures developed in a medium
strength model, while a significant number of small cracks emerged in the weak rock. The middle layer, which had high tensile
strength, remained stable. This suggests that the strong middle layer can transfer internal forces to the weaker rock after crack
propagation occurs in the upper layer, resulting in small crack growth in the soft rock. Additionally, the dip angles of the large
fracture sets related to the vertical axis were found to be 45 degrees. This study may contribute to the simulation of hydraulic
fracturing in oil shale reservoirs.
Key Words
analytical solution; bedding plane; hydraulic fractures; propagation behavior
Address
Jinwei Fu: School of Civil Engineering and Transportation, North China University of Water Resources and Electric Power,
Zhengzhou, 450046, China
Hadi Haeri: Department of Mining Engineering, Higher Education Complex of Zarand, Shahid Bahonar University of Kerman, Kerman, Iran
Vahab Sarfarazi, Shadman Mohammadi Bolbanabad and Shirin Jahanmiri: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Fariborz Matinpoor: Department of Mining Engineering, Tehran University, Tehran, Iran
Fatehi Marji: Department of Mine Exploitation Engineering, Faculty of Mining and metallurgy, Institute of Engineering, Yazd University, Yazd, Iran
Abstract
The empirical torque factor (Kt) is a critical parameter for predicting the ultimate compressive capacity of helical
piles from installation torque. However, current Kt values may be limited by the derivation from combined axial loads, an
exclusive reliance on shaft diameter, and the scarcity of adequate and diverse test data. This study introduces more robust and
reliable Kt correlations by developing models derived solely from compression load tests that integrate both the helical pile's
shaft diameter (d) and embedded area (EA). A total of 20 model helical piles were installed and loaded axially compression in
loose and dense sand to investigate installation torque-ultimate capacity behavior. The depth-torque profiles and loaddisplacement
curves were obtained from model laboratory tests for various helix diameters, numbers, and spacing. Furthermore,
installation torques (T) varying from torque reading methods (max., end pile, and average) were examined, and Kt values were
showed variations of approximately 10% with different T values. These results were synthesized with a comprehensive database
compiled from literature to create two extensive datasets correlating Kt with both shaft diameter and embedded area. The
proposed novel equations for calculating Kt demonstrate a strong statistical fit, with high coefficients of determination (R) of
0.94 and 0.90 for the d-based and EA-based correlations, respectively. These validated models offer a significant improvement
over existing methods, providing a sounder framework for the design of compression-loaded helical piles.
Address
Yakup Türedi, Muhammet Dingil, Murat Örnek and Abdulazim Yildiz: Department of Civil Engineering, Iskenderun Technical University, Hatay 31200, Türkiye
Buse Emirler: Department of Civil Engineering, Cukurova University, Adana 01250, Türkiye
Abstract
The improvement of marginal sites requires both technically appropriate and sustainable ground modification
techniques to mitigate the geotechnical issues associated with the site encountered. This study evaluated the response of soft clay
improved with an electrokinetic-assisted encased stone column. In this study, the stone columns were encased with conductive
natural geotextile to incorporate electrokinetic coupling, enhancing the clayey soil performance. The prepared electrokineticassisted
encased stone column acts as a cathode during the coupling process, and mild steel bars were used as an anode material.
The electrokinetic process was initiated by applying a voltage gradient across electrodes (i.e., anode and cathode). The research
highlights the impact of combining electrokinetics with an encased stone column (ESC) on the strength, deformation, and
physicochemical and structural response of clayey soil. During the experiment, the discharge of pore water, vertical deformation,
and current were continuously monitored to evaluate the method's effectiveness. At the culmination of the test, the reduction in
soil moisture, improvement in undrained shear strength, anode deterioration, and changes in the soil's physicochemical,
mineralogical, and structural properties were assessed. The results indicate that coupling electrokinetics with an ESC
significantly accelerates pore water removal efficiency, and approximately 14% higher settlement was observed for the 0.15
V/mm compared to the ESC case. The time to remove 95% of the total pore water was reduced by approximately 87% with a
voltage gradient of 0.15 V/mm compared to the ESC. The undrained shear strength increases with an increase in applied voltage
gradient and with depth. As compared to the ESC case, the undrained shear strength increases by 1.23, 1.43, 1.58, and 1.80 times
for applied voltage gradients of 0.025, 0.05, 0.10, and 0.15 V/mm. This study also shows significant changes in moisture
content, physicochemical properties, mineralogy, and soil structure.
Key Words
clay; electrokinetics; encased stone column; natural geotextile; strength; voltage gradient
Address
B.K. Pandey: Department of Civil Engineering, Guru Ghasidas Vishwavidyalaya, Koni, Bilaspur 495009, Chhattisgarh, India
S. Rajesh: Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India
Abstract
Seepage induced failure mechanisms such as base heave and piping pose serious challenges for the stability of
excavation pits in sandy soils. Conventional design approaches rely on Terzaghi's failure criterion and assume fully cohesionless
behavior, yet field evidence indicates that even trace cohesion arising from fines content, partial saturation or chemical bonding
can meaningfully alter seepage response. To address this gap, the present study employs hydraulically and mechanically coupled
axisymmetric finite element analyses to quantify the influence of low cohesion on heave behavior of circular sheeted pits. A
homogeneous sand layer is modeled with cohesion values ranging from 0 to 5 kPa, internal friction angles between 25 degrees
and 35 degrees and a range of dilation angles. Model results are systematically benchmarked against classical theoretical
predictions and reveal three distinct failure modes governed by the interaction of cohesion, friction angle and dilation angle.
Results demonstrate that the inclusion of even very low cohesion markedly raises the critical hydraulic gradient required to
initiate failure and thereby enhances pit stability. This work offers novel insight by highlighting the importance of incorporating
slight cohesion and realistic dilation behavior into seepage stability assessments for deep excavations and other key geotechnical
structures.
