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CONTENTS
Volume 35, Number 3, November10 2023
 

Abstract
As a new type of pile foundation, root piles have attracted more attention in the uplift design especially because of their unique structure. In this paper, based on the field tests the bearing capacity and load transfer law of straight pile, belled pile and roots pile were analysed. Results found the setting of multiple layers of roots along the pile depth can make the root resistance and skin friction resistance work simultaneously which improve the uplift resistance greatly. By using the numerical simulation tool, the uplift resistance of pile is analysed under the influence of different root length, density (number of roots) and spacing. It is found that increasing the root length and spacing can effectively improve the uplift resistance of the pile. However, the effect of increasing the spacing of roots is more significant. With increasing the roots density, the interaction development process between roots will assume to four main stages: stage I no interaction, stage II weak interaction, stage III strong interaction and stage IV strengthen. When the roots density is at stage II, there will be a high uplift resistance in addition to a little interaction. Finally, based on the load transfer method, a nonlinear deformation calculation method for the roots pile under uplift load were established. This method not only considered the influence of different stress conditions and roots positions on load distribution of roots, but also consider the influence of roots interaction at same layer and between layers on the uplift resistance.

Key Words
field test; nonlinear deformation; numerical simulation; root pile; uplift

Address
Jilu Zhang, Xiaohan Zhou and Xinrong Liu: School of Civil Engineering, Chongqing University, Chongqing 400045, China;
National Joint Engineering Research Center of Geohazards Prevention in The Reservoir Areas (Chongqing), Chongqing 400045, China
Xuefeng Huang: School of Civil Engineering, Lanzhou University of Technology, Lanzhou, 730050, China;
Department of Military Installations Engineering, Army Logistical University of PLA, Chongqing 401311, China
Jun Yuan: Northwest Electric Power Design Institute Co., Ltd. of China Power Engineering Consulting Group, Xi'an 710075, China
Xuelan Liang: Construction Branch of State Grid Qinghai Electric Power Company, Xining, 810001, China
Juan Li: Qinghai Power Transmission and Transfer Engineering Co. Ltd., Xining, 810000, China

Abstract
The effect of initial static shear ts on the dynamic characteristics of soil has been studied through extensive laboratory experiments over the past decades, but the influence of radial cyclic stress on its effect has rarely been considered. In this paper, a series of undrained triaxial tests were conducted to the saturated medium dense sand under axial and radial cyclic loadings with a phase difference of 180. It is shown that the medium dense sand mainly performs two typical deformation response modes, including the accumulated plastic strain and cyclic mobility. The compressive static shear is conducive to the liquefaction resistance, while the extensional one is on the contrary. Such effects are magnified as 0 p increases, though the absolute value of CRR reduces. The radial cyclic load leads to a higher Nf compared with the loading in the single axial direction, and significantly affects the generation of the pore pressure and its relationship with the accumulation of the axial strain. The samples with the compressive static shear are more sensitive to the strain failure criteria. But for samples with extensional static shear, the limiting residual pore pressure ratio ur, lim precedes before the strain failure. For geotechnical applications, it is necessary to comprehensively consider both the pore pressure and strain failure criteria.

Key Words
cyclic resistance; cyclic triaxial tests; failure criterion; pore pressure; saturated sand; static shear; vertical earthquakes

Address
Zhen-Dong Cui, Tian-Yu Sui, Dong-Tai She and Li Yuan: State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering,
China University of Mining and Technology, Xuzhou, Jiangsu 221116, P. R. China

Abstract
To calculate the pullout capacity of a shallow-buried inclined strip anchor plate in sloping rock ground, this paper constructed a curve uplift failure mechanism of rock mass above the anchor plate. In this mechanism, the plane strain hypothesis in elasto-plastic mechanics and the Hoek-Brown failure criterion were employed. Then, according to the upper bound method and variational principle, this paper deduced the analytical expressions for the rock failure surface equation and for the anchor plate's ultimate pullout capacity in the limit state. Further, based on an equivalent transformation method of Hoek-Brown failure criterion, this paper analyzed the influence laws of the embedment depth/width ratio, ground inclination, anchor plate inclination and generalized Hoek-Brown strength parameters on the anchor plate's ultimate pullout capacity and rock failure range. Finally, a series of numerical simulation for pullout failure processes of a strip anchor plate with six inclinations were carried out to verify the validity of the proposed theoretical method. The research work in this paper can provide some theoretical reference for design and construction of strip anchor plates in sloping rock ground.

Key Words
Hoek-Brown failure criterion; inclined anchor plate; sloping ground; pullout capacity; upper bound method

Address
Hong-tao Wang: School of Civil Engineering, Shandong Jianzhu University, Jinan, Shandong, China;
Jinan Rail Transit Group Co., Ltd., Jinan, Shandong, China
Fu-qiang Fan: School of Civil Engineering, Shandong Jianzhu University, Jinan, Shandong, China;
Shandong Jigang Environmental Protection New Materials Co., Ltd., Jinan, Shandong, China
Yan-qing Men: Jinan Rail Transit Group Co., Ltd., Jinan, Shandong, China
Hong-jun Zhang: Shandong Geological Sci. Institute, Jinan, Shandong, China
Xue-lei Xie: School of Civil Engineering, Shandong Jianzhu University, Jinan, Shandong, China

Abstract
This study aims to investigate the failure mechanism and uplift capacity of a belled pile embedded in soft rock. The laboratory model test for evaluating the uplift capacity of a belled pile at the circular chamber was conducted for two belled angles (0 and 12) and penetration depths (160 mm and 80 mm) under the same strength condition on soft-rock ground. In addition, to investigate the failure mechanism of the belled pile, the failure behavior of the belled pile embedded in soft-rock ground was analyzed under different conditions of the belled angle (12 and 30) and strength at the soft-rock ground (0.3 MPa and 1 MPa) via image analysis in a half-circular chamber. A higher belled angle and ground strength resulted in a higher uplift capacity under the same penetration depth. In addition, the uplift capacity under the same belled angle and ground strength increased with penetration depth. For the image analysis, the shape of the failure surface was an inverted cone regardless of the test conditions. In addition, the failure mechanism was observed in three stages: (a) static, (b) compression, and (c) formation of the failure surface. A new predictive model for the uplift capacity of the belled pile applicable to the soft-rock ground was proposed based on the result. In addition, the predicted value was in good agreement with the measured value. Therefore, this model can be very useful for estimating the uplift capacity of a belled pile embedded in soft-rock ground.

Key Words
belled pile; failure mechanism; predictive model; soft-rock; uplift capacity

Address
Gyeong-o Kang and Jung-goo Kang: Department of Civil Engineering, Gwangju University, 277 Hyodeck-ro, Nam-gu, Gwangju, 61743, Republic of Korea
Young-sang Kim: Department of Civil Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Republic of Korea
Jaehong Kim: Department of Civil Engineering, Dongshin University, 67 Dongsindae-gil, Naju-si, Jeollanam-do, 58245, Republic of Korea

Abstract
The present study explores the impact of strip footing's ultimate load-carrying capacity on granular soil under oblique loads. At the same time, it is lined up subsequently nearer to the existing footing. The numerical simulations have been done by finite element limit analysis (FELA). Upper-bound (UB), lower-bound (LB) and adaptive mesh refinement proficiencies have been harnessed to predict the précised solution for assessing the new footing ultimate load-carrying capacity under oblique loading while lined up subsequently nearer to vertically loaded existing footing. The impact of the new footing's ultimate load-carrying capacity has been well-considered by considering characteristics such as load inclination, angle of internal friction of the soil, footing width and spacing between the footings. The outcome of the current numerical analysis for isolated footing and interfering footing has been validated using accessible literature. For various soil friction angles, load inclination on the new footing interference (s) factors was computed using different spacing ratios for symmetrical and asymmetrical footing widths. The charts were developed for the new footing lined up nearer to the existing footing in response to interference factor that varies with the spacing ratio, load inclination and width ratio of the new footing.

Key Words
adaptive mesh refinement; design charts; FELA; interference effect; upper-bound and lower-bound

Address
R. Sarvesh, V. Srinivasan and Anjan Patel: Department of Civil Engineering, Visvesvaraya National Institute of Technology, Nagpur – 440 010, India

Abstract
In this article, a two-phase random medium is assumed for geometric interfaces between rock and soil based on Gaussian field and piezoelectric layer. The structure is modeled by thick plate mathematically and the numerical model is applied to approximation the statistical features of the safety. The elastic medium is simulated with two parameters of spring and shear. The structure is modelled by sinusoidal shear deformation theory (SSDT) and by utilizing the energy method, the final governing equations are derived. Using differential quadrature method, the motion equations are solved for obtaining the failure mode of the rock-soil slope. The results show that the safety factor of rock is dependent to the soil volume faction significantly. Numerical results show that as the structure length is increased, the safety load is decreased. In addition, the application of negative voltage improves the safety of the structure.

Key Words
mathematical model; numerical method; rock-soil; stability

Address
Shan Hua and S.S. Wang: School of Earth Science and Resources, Chang'an University, Xi'an, Shaanxi,710064, China
Maryam Shokravi: Department of Education, Mehrab High School, Saveh, Iran

Abstract
In this study, a dynamic p-y curve method for the seismic design of laterally loaded pile in clay was proposed focusing on the direct application of the cone penetration test (CPT) result. Key motivation of this study was to fully utilize the continuous and in-situ profiling capability of CPT, which was particularly effective for multi-layered, heterogeneous soil conditions and offshore environment. The exerted dynamic load response of pile was expressed and obtained by introducing the static stiffness and damping of clay into the dynamic p-y curve function, both formulated as a function of the cone resistance. The proposed CPT-based dynamic p-y curve function was employed in the pseudo-static analysis based on an equivalent static-load approach. A calculation algorithm was prepared to implement the proposed method, following the procedure of the pseudo-static analysis. Case examples were selected, including centrifuge tests and field load tests, and adopted to compare measured and predicted dynamic pile load responses. The compared results of the case examples confirmed that the proposed method was effective and beneficial for the seismic design of piles in clay.

Key Words
clay; cone penetration test; pseudo-static analysis; p-y analysis; seismic design of pile

Address
Garam Kim: Research Institute of Korea Electric Power Corporation, Naju 58263, Republic of Korea
Jiyeong Lee, Jonghyeog Yoon, Qaisar Abbas and Junhwan Lee: School of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, Republic of Korea

Abstract
The conventional direct shear apparatus has been widely used to analyze the shear behavior of the soil-soil and soil-solid interfaces. However, it has certain limitations, such as tilting of loading plate and rotation of upper shear box, which eventually lead to unfavorable shear responses and hinder the evaluation of accurate shear strength parameters. Therefore, in this study the direct shear apparatus is modified as follows: (1) application of constant vertical stress through a loading rod fixed to a circular loading plate for soil-soil tests and rectangular loading plate for interface testing; and (2) a provision of linear motion (LM) guide for smooth horizontal movement of shear box during shearing process and construction of upper and lower shear boxes for soil-solid interface testing. The modified direct shear apparatus is tested with soil-soil at different initial relative densities and interface testing using solid plate under three vertical stresses. The experimental results confirm that the vertical stress, which is imposed through the new loading system, remains constant during the shearing phase. Further analysis is conducted to establish the empirical relation of friction angle as a function of initial relative density.

Key Words
constant vertical stress; friction angle; initial relative density; modified direct shear apparatus; rotation of upper shear box; tilting of loading plate

Address
Muhammad Naqeeb Nawaz, Seung-Hun Lee and Song-Hun Chong: Department of Civil Engineering, Sunchon National University, 255, Jungang-ro, Sunchon-si, Jeollanam-do, 57922, Republic of Korea
Jae-Hong Kim: Department of Civil and Environmental Engineering, Dongshin University, 67, Dongshindae-gil,
Naju-si, Jeollanam-do, 58245, Republic of Korea


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