Abstract
Undrained stability of slopes has long been of interest to the community of geotechnical engineering due to its
practical importance. However, the role of the undrained shear strength cu in the seismic stability and failure geometry of slopes
under three-dimensional (3D) condition has not been fully understood. Therefore, this study adopts a modified 3D rotational
failure mechanism to develop the upper bound solution to the stability number Ns for slopes with linearly increasing cu with
depth based on the kinematic approach of limit analysis. The seismic force is included using the pseudo-static method. Three
types of failure mechanisms, i.e., the toe failure, face failure and below-toe failure are considered to capture the critical
condition. Stability charts that cover a wide range of parameters and representative failure surfaces are then developed to
illustrate the influence of key factors. Results show that the stability and failure geometry of slopes are significantly influenced
by the variation ratio of cu with depth. The most significant outcome is that an increase in the horizontal seismic coefficient kh leads to a shallower critical failure surface when the slope with a large variation ratio of cu is constrained within a narrow width.
Key Words
3D slope stability; failure mechanism; limit analysis; undrained shear strength
Address
Yunwei Shi, Xianqi Luo and Pingfan Wang: School of Ocean & Civil Engineering, Shanghai Jiao Tong University,
800 Dongchuan Road, Minhang District, Shanghai, China
Abstract
This study aims to investigate the impact of polyvinyl chloride (PVC) waste granules from discarded pipes on the
uniaxial compressive strength (UCS) of two clayey soils using various mixing ratios. Soil 1 and Soil 2 were sourced from El-
Idrissia and central Djelfa, Algeria, respectively.PVC granules (0%, 0.5%, 1%, 2%, and 10%) were mixed with dry clay soil, and
UCS tests showed that PVC granules enhanced soil strength. Adding 0.5% and 5% PVC to Soil 1 increased UCS by 6.84% and
46.58%, respectively, making these values 1.5 times higher than unreinforced soil. For Soil 2, UCS increased by 14.62% and
88.46% with the same PVC proportions, over twice the strength of soil without PVC. PVC granules improved the compressive
strength and resistance of clayey soils, enhanced their ductility noticeably, and prevented crack propagation and soil
deformation. Microscopic analysis revealed significant interactions between PVC surfaces and clay particles, positively
impacting soil behavior. Stabilizing clay soil with PVC waste produced isotropic materials with fewer desiccation cracks,
improving compressive strength. This study offers practical applications for reinforcing weak soils in infrastructure, foundations,
and road materials, providing significant economic and environmental benefits.
Address
Melik Bekhiti: Department of Civil Engineering, University of Djelfa, Algeria;
Civil Engineering and Environmental Laboratory, Sidi Bel Abbes University, Algeria
Abdelhalim Bensaada: Civil engineering and environmental protection laboratory (LGPE), Civil Engineering Department,
Faculty of Technology, University of Medea, Algeria
Abstract
Tunnel excavation induces stress redistribution in the surrounding rock, forming a bearing arch to sustain ground
stress. As a typical and special type of rock formation, the bearing arch morphology in (approximately) horizontally layered
surrounding rock remains unclear due to the influence of structural planes. Additionally, the effects of factors such as ground
stress, layer thickness, and interlayer contact conditions on the distribution of the bearing arch are not well understood. To
address this issue, non-contact strain acquisition experiments combined with numerical calculations were used to determine the
morphology of the bearing arch, followed by sensitivity analysis of the parameters. The results indicate that non-uniform rock
masses under unfavorable stress conditions may fail at stress levels far below the ultimate strength of the rock blocks. For
tunnels excavated in horizontally layered surrounding rock, vertical loads easily cause bending-induced tensile stress in the roof
and floor, while increasing initial horizontal stress improves the bearing condition. The bearing arch in horizontally layered
surrounding rock exhibits two extreme states after excavation: "butterfly-shaped" and "rounded rectangular." Under extreme
conditions, "bearing zone discontinuity" may occur in the vertical direction. Overall, the lateral pressure coefficient and
interlayer bonding strength significantly influence the bearing arch, while the layer thickness has a relatively smaller effect. The
lateral pressure coefficient mainly affects the arch's morphology, while interlayer bonding strength and layer thickness primarily
influence the stress redistribution during the post-excavation stress equilibrium process. In practical tunnel engineering,
engineering measures should aim to enhance the overall integrity of the surrounding rock to fully utilize the bearing arch effect.
Key Words
bearing arch; distribution characteristics; horizontal layered surrounding rock; influencing factors;
morphology characteristics; tunnel excavation
Address
Pengtao Chen, Junru Zhang and Jianchi Ma, Yi Dai and Tong Pan: School of Civil Engineering, Southwest Jiaotong University, No 111, Section 1 North, Second Ring Road, Chengdu 610031, China;
Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University,
No 111, Section 1 North, Second Ring Road, Chengdu 610031, China
Kaimeng Ma: School of Civil Engineering, Southwest Jiaotong University, No 111, Section 1 North, Second Ring Road, Chengdu 610031, China;
School of Civil Engineering, Shijiazhuang Tiedao University, No. 17, North Second Ring East Road, Shijiazhuang 050043, China
Zhiyi Jin: School of Civil Engineering, Southwest Jiaotong University, No 111, Section 1 North, Second Ring Road, Chengdu 610031, China;
College of Civil Engineering and Architecture, Xinjiang University, No. 777, Huarui Street, Urumqi 830047, China
Abstract
The present study evaluates the active earth thrust exerted by sandy sloping ground on rigid retaining walls,
investigating the critical effects of slope toe position (e) and slope height (h) that are often neglected in current design standards
despite their significant influence on wall pressures. The solutions were obtained by performing finite element lower bound limit
analysis with second order conic optimization techniques and presented in the form of non-dimensional earth pressure
coefficient (Ka). The active earth thrust remains constant beyond a certain distance of slope toe from the back face wall, and
height of slope, which are defined as critical toe distance (ecr) and critical slope height (hcr), respectively. The critical toe distance
and slope height have been found to be influenced by the friction angle of soil (o), inclination of slope (B) and surcharge pressure
(q) on the ground surface. The study shows that the magnitudes of Ka, ecr, and hcr increase with a reduction in the values of o and
with an increase in the values of B and q. For a few typical cases, the proximity of stress state to failure was presented.
Key Words
active thrust; finite elements; limit analysis; retaining wall; sand; slope
Address
Sunil Khuntia: Department of Civil Engineering, National Institute of Technology Rourkela 769008, India
Jagdish Prasad Sahoo: Department of Civil Engineering, Indian Institute of Technology Kanpur 208016, India
Abstract
The determination of Atterberg limits (LL and PL) holds significant importance in geotechnical studies. Setting of
these parameters properly enables important engineering behaviors of soils to be easily predicted. However, these methods have
many limitations and uncertainties. These drawbacks of the test methods affect the results significantly. Likewise Atterberg
limits, the undrained shear strength (su) which represents the total shear strength of soils may also be crucially important in
certain geotechnical studies. Determining the su of soils is sometimes very challenging, especially for very weak soils due to
sampling difficulties. This investigation aims to use the Mud Press Machine with a very significant number of soils to determine
the Atterberg limits and su simultaneously. For this purpose, 500 sets of tests were carried out on 100 different soil samples with
a very wide range of plasticity. Multivariate regression analyses were performed between the force values obtained from the
MPM tests and the other three parameters (LL, PL and su) obtained from the conventional tests and the relationships between
them were examined. Notably high correlations were observed between the MPM results and the conventional tests. The results
indicate that the MPM device can determine both the Atterberg limits and undrained shear strength of soils in one simple test and
the uncertainties and difficulties in other methods can be overcome with this innovative method.
Key Words
Atterberg limits; fall cone test; mud press machine; undrained shear strength; vane shear test
Address
Kamil Kayabali: Department of Geological Enginering, Ankara University, Ankara, Türkiye
Emre Pinarc:Department of Geological Enginering, Ankara University, Ankara, Türkiye;
Department of Geological Enginering, Çukurova University, Adana, Türkiye
Abstract
This study presents an investigation into the reuse potential of waste brick powder (WBP), a cost-effective,
environmentally friendly, and easy-to-use waste-based geopolymer for soil improvement as a grouting material. The WBP was
obtained by crushing and sieving waste brick to produce the recycled aluminosilicate starting material. Various factors, including
liquid-to-solid ratios (1.5, 2.0, and 2.5), NaOH molarities (4, 8, 12, and 16), types of soils, and aging (7, 28, and 365 days), were
comprehensively investigated to gain insight into the usability of WBP in soil injection. The effect of alkali-activated waste brick
powder (AAWBP) on the mechanical strength and injectability of the soils was assessed, as well as the influence of these factors
on the microstructure of samples. The primary structure of AAWBP was determined to be the C-S-H gel, which significantly
enhanced the strength development of soil samples. The compressive strength of geopolymer-treated S1, S2, and S3 soil samples
reached 4.72, 3.79, and 2.5 MPa after 365 days, respectively, significantly higher than the samples at 28 days (3.32, 1.00, and
0.61 MPa, respectively). Moreover, the strength of samples increased with a decrease in the liquid-solid ratio in all samples,
whereas it increased with a rise in the concentration of the activator up to 8 molar for S2 and S3 soil and up to 12 molar for S1
soil. Also, reducing soil particle size positively influenced the development of strength characteristics.
Address
Ahmet Naldan: Graduate School of Natural and Applied Sciences, Department of Civil Engineering,
Erzincan Binali Yildirim University, Erzincan, Türkiye
Harun Akoğuz: Department of Civil Engineering, Faculty of Engineering and Architecture, Erzincan Binali Yildirim University, Erzincan, Türkiye
Bülent Çağla: Department of Food, Feed and Medicine, Institute of Hemp Research, Ondokuz Mayis University, Samsun, Türkiye
