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CONTENTS
Volume 35, Number 1, October10 2023
 

Abstract
A growing trend of utilizing helical piles for soft soil strata to support infrastructure projects is currently observed in Saemangeum, South Korea. Recognized mainly due to its ease of installation and reusability proves to be far more superior compared to other foundation types in terms of sustainability. This study applies modified p-y springs to characterize the behavior of a laterally loaded helical pile with a shaft diameter of 89.1 mm affixed with 3 helices evenly spaced along its embedded length of 2.5 m. Geotechnical soil properties are correlated from CPT data near the test bed vicinity and strain gauges mounted on the shaft surface. A modification factor is applied on the p-y springs to adjust the simulated data and match it to the bending moment, soil resistance and deflection values from the strain gauge measurements. The predicted lateral behavior of the helical pile through the numerical analysis method shows fairly good agreement to the recorded field test results.

Key Words
CPT; helical piles; instrumented piles; p-y springs; static lateral load test

Address
Hyeong-Joo Kim: Department of Civil Engineering, Kunsan National University, 558 Daehak-ro, Miryong-dong, Gunsan 54150, Republic of Korea
Hyeong-Soo Kim, James Vincent Reyes, Yeong-Seong Jeong, Jun-Yong Park and Kevin Bagas Arifki Mawuntu: Department of Civil and Environmental Engineering, Kunsan National University, 558 Daehak-ro,
Miryong-dong, Gunsan 54150, Republic of Korea
Peter Rey Dinoy: Renewable Energy Research Institute, Kunsan National University, 558 Daehak-ro, Miryong-dong, Gunsan 54150, Republic of Korea

Abstract
The model production for large-scale (lateral length > 2.0 m) capillary barrier (CB) model tests is time and costintensive. To address these limitations, the framework of a small-scale CB (SSCB) model test under the lateral no-flow condition has been established. In this study, to validate the experimental methodology of the SSCB model test, a series of seepage analyses on the SSCB model test and engineered slopes in the same and additional test conditions was performed. First, the seepage behavior and diversion length (LD) of the CB system were investigated under three rainfall conditions. In the seepage analysis for the engineered slopes with different slope angles and sand layer thicknesses, the LD increased with the increase in the slope angle and sand layer thickness, although the increase rate of the LD with the sand layer thickness exhibited an upper limit. The LD values from the seepage analysis agreed well with the results estimated from the laboratory SSCB mode test. Therefore, it can be concluded that the experimental methodology of the SSCB model test is one of the promising alternatives to efficiently evaluate the water-shielding performance of the CB system for an engineered slope.

Key Words
CB model test; diversion length; lateral no-flow condition; seepage analysis; small-scale capillary barrier

Address
Byeong-Su Kim: Department of Civil & Environmental Engineering, Dankook University,
152, Jukjeon-ro, Suji-gu, Yongin City, Gyeonggi-do 16890, Korea

Abstract
As the intensity of urban underground space development increases, more and more tunnels are planned and constructed, and sometimes it is inevitable to encounter situations where tunnels have to underpass the river embankments. Most previous studies involved tunnels passing river embankments perpendicularly or with large intersection angle. In this study, a project case where two EPB shield tunnels with 8.82 m diameter run parallelly underneath a river embankment was reported. The parallel length is 380 m and tunnel were mainly buried in the moderate / slightly weathered clastic rock layer. The field monitoring result was presented and discussed. Three-dimensional back-analysis were then carried out to gain a better understanding the interaction mechanisms between shield tunnel and embankment and further to predict the ultimate settlement of embankment due to twin-tunnel excavation. Parametrical studies considering effect of tunnel face pressure, tail grouting pressure and volume loss were also conducted. The measured embankment settlement after the single tunnel excavation was 4.53 mm ~ 7.43 mm. Neither new crack on the pavement or cavity under the roadbed was observed. It is found that the more degree of weathering of the rock around the tunnel, the greater the embankment settlement and wider the settlement trough. Besides, the latter tunnel excavation might cause larger deformation than the former tunnel excavation if the mobilized plastic zone overlapped. With given geometry and stratigraphic condition in this study, the safety or serviceability of the river embankment would hardly be affected since the ultimate settlement of the embankment after the twin-tunnel excavation is within the allowable limit. Reasonable tunnel face pressure and tail grouting pressure can to some extent suppress the settlement of the embankment. The recommended tunnel face pressure and tail grouting pressure are 300 kPa and 550 kPa in this study, respectively. However, the volume loss plays the crucial role in the tunnel-embankment interaction. Controlling and compensating the tunneling induced volume loss is the most effective measure for river embankment protection. Additionally, reinforcing the embankment with cement mixing pile in advance is an alternative option in case the predicted settlement exceeds allowable limit.

Key Words
field monitoring; river embankment; settlement control; shield tunnel; three-dimensional numerical analysis

Address
Li'ang Chen, Lingwei Lu, Zhiyang Tang and Shixuan Yi: Guangzhou Metro Design&Research Institute Co.,Ltd., Guangzhou, Guangdong, P.R. China
Qingkai Wang: Zhongshan Municipal People's Government Office, Zhongshan, Guangdong, P.R. China
Zhibo Chen: Zijin School of Geology and Mining Fuzhou University, Fujian, P.R. China

Abstract
The use of a skirt, a vertical projection attached to the footing, is a recently developed method to increase the bearing capacity of soils and reduce foundation settlements. Most of the studies were focused on vertical skirted circular footings resting on clay while neglecting the rigidity and inclination of skirts. This study employs finite element limit analysis to investigate the bearing capacity enhancement of flexible and rigid inclined skirts in cohesionless soils. The results indicate that the bearing capacity initially improves with an increase in the skirt inclination but subsequently decreases for both flexible and rigid skirts. However, the rigid skirt exhibits more apparent optimum skirt inclination and bearing capacity enhancement than the flexible one, owing to differences in their failure mechanisms. Furthermore, the bearing capacity of the inclined skirted foundation increases with the skirt length, footing depth, and internal friction angle of the soil. In the case of rigid skirts, the bearing capacity increases linearly with skirt length, while for flexible skirts, it reaches a stable value at a certain skirt length. The efficiency of the flexible footing reduces as the footing depth and soil internal friction angle increase. Conversely, the efficiency of the rigid skirt decreases only with an increase in the depth of the footing. The paper also presents a detailed analysis of various failure patterns, highlighting the behaviour of inclined skirted footings. Additionally, nonlinear regression equations are provided to quantify and predict the bearing capacity enhancement with the inclined skirts.

Key Words
bearing capacity; enhancement factor; footing; inclined skirt; soil

Address
Rajesh P. Shukla: Department of Civil Engineering, National Institute of Technology, Srinagar, India, 190006
Ravi S. Jakka: Department of Earthquake Engineering, IIT Roorkee, Roorkee, India, 247667

Abstract
Soft clay is widely spread in nature and encountered in geotechnical engineering applications. The creep property of soft clay greatly affects the long-term performance of its upper structures. Therefore, it is vital to establish a reasonable and practical creep constitutive model. In the study, two updated hyperbolic equations based on the volumetric creep and deviatoric creep are respectively proposed. Subsequently, three creep constitutive models based on different creep behavior, i.e., V-model (use volumetric creep equation), D-model (use deviatoric creep equation) and VD-model (use both volumetric and deviatoric creep equations) are developed and compared. From the aspect of prediction accuracy, both V-model and D-model show good agreements with experimental results, while the predictions of the VD-model are smaller than the experimental results. In terms of the parametric sensitivity, D-model and VD-model are lower sensitive to parameter M (the slope of the critical state line) than V-model. Therefore, the D-model which is developed by incorporating the updated deviatoric creep equation is suggested in engineering applications.

Key Words
creep constitutive model; deviator creep; hyperbolic equation; soft clay; volumetric creep

Address
Chen Ge and Zhu Jungao: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, China
Li Jian: Chengdu Engineering Corporation Limited, Chengdu 610072, China;
Huaneng Tibet Hydropower Safety Engineering Technology Research Center, Beijingxi Road, Tibet 850000, China
Wu Gang: Huaneng Tibet Yarlungzangbo River Hydropower Development and Investment Co. Ltd, Beijingxi Road, Tibet 850000, China;
Huaneng Tibet Hydropower Safety Engineering Technology Research Center, Beijingxi Road, Tibet 850000, China
Guo Wanli: Geotechnical Engineering Department, Nanjing Hydraulic Research Institute, Nanjing 210024, China

Abstract
Due to the nature of the conjunctive Cone Penetration Test(CPT), which does not verify the actual sample directly, geotechnical engineers commonly classify the underground geomaterials using CPT results with the classification diagrams proposed by various researchers. However, such classification diagrams may fail to reflect local geotechnical characteristics, potentially resulting in misclassification that does not align with the actual stratification in regions with strong local features. To address this, this paper presents an objective method for more accurate local CPT soil classification criteria, which utilizes C4.5 decision tree models trained with the CPT results from the clay-dominant southern coast of Korea and the sand-dominant region in South Carolina, USA. The results and analyses demonstrate that the C4.5 algorithm, in conjunction with oversampling, outlier removal, and pruning methods, can enhance and optimize the decision tree-based CPT soil classification model.

Key Words
cone penetration test; data mining; decision tree model; machine learning; soil classification; stratification

Address
Junghee Park: Department of Civil and Environmental Engineering, Incheon National University, Incheon 22012, Republic of Korea
So-Hyun Cho and Hyun-Ki Kim: Department of Civil and Environmental Engineering, Kookmin University, Seoul 02707, Republic of Korea
Jong-Sub Lee: School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Republic of Korea

Abstract
Due to the unclear mechanism of the influence of temperature on the resonance problem of doubly curved shells, this article aims to explore this issue. When the ambient temperature rises, the composite structure will expand. If the thermal effects are considered, the resonance response will become more complex. In the design of structure, thermal effect is inevitable. Therefore, it is of significance to study the resonant behavior of doubly curved shell structures in thermal environment. In view of this, this paper extends the previous work (She and Ding 2023) to the case of the nonlinear principal resonance behavior of graphene platelet reinforced metal foams (GPLRMFs) doubly curved shells in thermal environment. The effect of uniform temperature field is taken into consideration in the constitutive equation, and the nonlinear motion control equation considering temperature effect is derived. The modified Lindstedt Poincare (MLP) method is used to obtain the resonance response of doubly curved shells. Finally, we study the effects of temperature changes, shell types, material parameters, initial geometric imperfection and prestress on the forced vibration behaviors. It can be found that, as the temperature goes up, the resonance position can be advanced.

Key Words
doubly curved shells; geometric imperfection; graphene platelet reinforced metal foams; resonance; thermal effects

Address
Jiaqin Xu and Gui-Lin She: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China

Abstract
Soft soil ground is a crucial factor limiting the development of the construction of transportation infrastructure in coastal areas. Soft soil is characterized by low strength, low permeability and high compressibility. However, the ordinary treatment method uses Portland cement to solidify the soft soil, which has low early strength and requires a long curing time. Microbially induced carbonate precipitation (MICP) is an emerging method to address geo-environmental problems associated with geotechnical materials. In this study, a method of bio-cementitious mortars consisting of MICP and cement was proposed to stabilize the soft soil. A series of laboratory tests were conducted on MICP-treated and cement-MICP-treated (C-MICP-treated) soft soils to improve mechanical properties. Microscale observations were also undertaken to reveal the underlying mechanism of cement-soil treated by MICP. The results showed that cohesion and internal friction angles of MICP-treated soft soil were greater than those of remolded soft soil. The UCS, elastic modulus and toughness of C-MICP-treated soft soil with high moisture content (50%, 60%, 70%, 80%) were improved compared to traditional cement-soil. A remarkable difference was observed that the MICP process mainly played a role in the early curing stage (i.e., within 14 days) while cement hydration continued during the whole process. Micro-characterization revealed that the calcium carbonate filling the pores enhanced the soft soil.

Key Words
cement-soil; mechanical properties; MICP; soft soil foundation

Address
Shuang Li, Ming Huang, Mingjuan Cui and Kai Xu: College of Civil Engineering, Fuzhou University, Fuzhou 350108, Fujian, China
Peng Lin and Liudi Xu: Department of Civil and Environmental Engineering, Shantou University, Shantou, 515063 Guangdong, China

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