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CONTENTS
Volume 26, Number 3, August10 2021
 

Abstract
To investigate the settlement characteristics of drilled shaft socketed into igneous, metamorphic, or sedimentary rock, experimental results of the pile load tests were thoroughly collected in 20 different locations, clearly tabulated, and extensively compared with the standards for assessment of ultimate load. Total and elastic settlement patterns of drill shaft were completely dependent on the socketed pile length, the imposed load, the pile diameter, and the shear stress in bedrock, whereas residual settlement did not depend on the factors. It was also observed that the trends of total, residual, and elastic settlements were independent on bedrock types. Comparison between the experimental data and the standards shows that the total and residual settlements of large drilled shaft socketed in bedrock were too high to determine the ultimate load, and the reasonable amount of total or residual settlement measured from pile load test is proposed to assess the ultimate load capacity of drilled shaft socketed in bedrock.

Key Words
bedrock; drilled shaft; pile load test; residual and total settlement; ultimate load capacity

Address
Won Pyo Hong: Department of Civil, Environmental and Plant Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Republic of Korea

Seongwon Hong: Department of Safety Engineering, Korea National University of Transportation, 50 Daehak-ro, Chungju-si, Chungbuk 27469, Republic of Korea


Abstract
The study of failure mode for the soil in front of a shield tunnel face is a key challenge for tunnel engineering, especially when drilling under the water table. This work aims to study face stability of a shield tunnel under the water table based on an blow-out failure mechanism in the framework of the upper bound theorem of limit analysis in conjunction with variational principle. The seepage force in the seepage field is derived, and seepage force is regarded as an external force which is introduced in the upper bound calculation. Based on the failure characteristic of the blow-out failure for the soil in front of a shield tunnel face, a upper bound failure mechanism is constructed. Using this mechanism, the equation of the failure surface is obtained and the shapes of the failure surfaces for different parameters are plotted. By studying the influence of various parameters on the shape of failure surfaces, the changing laws of the shape of the failure surface for different parameters are obtained.

Key Words
blow-out failure mechanism; Hoek-Brown failure criterion; limit analysis theorem; seepage force

Address
Fu Huang, Di Wang, Nan Xiao and Ruo-chen Ou: School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, Hunan, China

Abstract
Predicting the frozen zone near the freezing pipe in artificial ground freezing (AGF) is critical in estimating the efficiency of the AGF technique. However, the complexity and uncertainty of many factors affecting the ground temperature cause difficulty in developing a reliable physical model for predicting the ground temperature. This study proposed a data-driven framework to accurately predict the ground temperature during the operation of AGF. Random forest (RF) and extreme gradient boosting (XGB) techniques were employed to develop the prediction model using the dataset of a field experiment in the silty deposit. The developed ensemble models showed relatively good performance (R2 > 0.96), yet the XGB model showed higher accuracy than the RF model. In addition, the evaluated mutual information and importance score revealed that the environmental attributes (ambient temperature, surface temperature, humidity, and wind speed) can be critical in predicting ground temperature during the AFG operation. The prediction models presented in this study can be utilized in evaluating freezing efficiency at the range of geotechnical and environmental attributes.

Key Words
artificial ground freezing; data-driven framework; extreme gradient boosting; mutual information; random forest

Address
Khanh Pham: 1.) Department of Civil Engineering, International University, Ho Chi Minh City, Vietnam
2.) Vietnam National University, Ho Chi Minh City, Vietnam

Sangyeong Park and Hangseok Choi: School of Civil, Environmental, & Architectural Engineering, Korea University, Seoul, 02841, Republic of Korea

Jongmuk Won: Department of Civil and Environmental Engineering, University of Ulsan, Ulsan, 44610, Republic of Korea

Abstract
Vibration investigation of rotating functionally graded cylindrical shells with fraction laws is studied here. Shell motion equations are framed according to the orthotropic Winkler-like model. For isotropic materials, the physical properties are same everywhere where the laminated and functionally graded materials, they vary from point to point. The influence of the polynomial, exponential and trigonometric fraction laws is investigated with simply supported condition. Also the variations have been plotted against the circumferential wave mode, length-to-radius and height-to-radius ratio. Moreover, backward and forward frequency pattern is observed increasing and decreasing for the various position of angular speed. The frequency first increases and gain maximum value for circumferential wave number. It is also exhibited that the effect of frequencies is investigated by varying the surfaces with stainless steel and nickel as a constituent material. The frequencies of trigonometric law is less than remaining laws.

Key Words
circumferential wave mode; FGM; length-to-radius ratio; simply supported; Winkler-like model

Address
Mohamed Amine Khadimallah: 1.) Department of Civil Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj, 16273, Saudi Arabia
2.) Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia

Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan

Ahmad Yahya: Nuclear Engineering Department, King Abdulaziz University, Jeddah, Saudi Arabia

Elaloui Elimame: Laboratory of Materials Applications in Environment, Water and Energy LR21ES15, Faculty of Sciences, University of Gafsa, Tunisia

Abdelouahed Tounsi: 1.) Yonsei Frontier Lab, Yonsei University, Seoul, Korea
2.) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
The objective of this study is to investigate the effects of incorporating inclined base plates on the end bearing capacities of embedded piles by conducting dynamic pile tests and static load tests. Two types of embedded piles were prepared – conventional piles with a 50-cm-diameter flat base plate and piles with a 56-cm-diameter inclined base plate. The dynamic pile tests were conducted during pile construction, and the static load tests were conducted after curing the cement paste to investigate the end bearing capacities of the test piles. Test results indicate that the base resistances of piles with inclined base plates are greater than those of conventional piles and that the base resistances increase with an increase in the inclination angle. The increased projected area, increased contact area, extended rupture surface, and enhanced slime discharge due to the inclined base plate may result in an increase in the end bearing capacity of the pile. This study demonstrates that the end bearing capacities of the embedded piles may be maximized by incorporating inclined plates to the pile base. Thus, the pile with the inclined base plate may be effectively used for the construction of embedded piles.

Key Words
dynamic pile test (DPT); embedded pile; end bearing capacity; inclined base plate; static load test (SLT)

Address
Mi Jeong Seo and Jong-Sub Lee: School of Civil, Environmental and Architectural Engineering, Korea University,145, Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea

Kyungsoo Han: Lyles School of Civil Engineering, Purdue University,550, Stadium Mall Drive, West Lafayette, Indiana, 47907, U.S.A.

Jong-Bae Park: Land and Housing Institute, Korea Land & Housing Corporation,99, Expo-ro 539beon-gil, Yuseong-gu, Daejeon, 34047, Republic of Korea

Kyeong-Han Jeong: The Dream ENC, 361, Simin-daero, Dongan-gu, Anyang-si, Gyeonggi-do, 14057, Republic of Korea

Abstract
Subgrade loess in arid and semi-arid regions subjected to high-suction conditions owing to low relative humidity and deep groundwater levels. Understanding the hydromechanical behavior of unsaturated compacted loess over a wide suction range is critical for resolving infrastructure problems in such areas. In this study, the water retention behavior of loess was investigated by imposing or measuring suction (s) using the axis translation technique, vapor equilibrium technique, and chilled mirror dew point technique. Triaxial tests were also performed to study the mechanical behavior of compacted loess under different net cell pressures (σ3n).The soil-water retention curves obtained using the different techniques are consistent. The degree of saturation and water content decreases significantly when s < 240 kPa, whereas the change of void ratio is relatively small. The water content versus s curves with different initial dry densities is coincident when s > 0.5 MPa, indicating that undrained triaxial tests can be considered as those under constant suction. For the same σ3n, specimens show strain-hardening, shrinkage, and drum-shaped shear failure under low-s conditions and strain-softening, dilatancy, and oblique section splitting under high-s conditions. The failure deviator stress and cohesion of the compacted loess specimens increase with increasing s over the full s range (0–299.37 MPa). An equation to predict the shear strength of unsaturated loess over a wide s range is proposed. The intersection of the capillary water retention curve and adsorption water retention curve is set as a reference point (sR), where capillary degree of saturation is applicable for s ≤ sR and adsorption degree of saturation is added for s > sR. The predicted and measured shear strengths of the compacted loess specimens are in good agreement.

Key Words
adsorption degree of saturation; capillary degree of saturation; prediction; shear strength; soil-water retention curve; unsaturated loess; wide suction range

Address
Tong Jiang, Jindi Zhao, Junran Zhang, Lijin Wang, Chenyu Song and Tianya Zhai: Henan Province Key Laboratory of Geomechanics and Structural Engineering, North China University of Water Resources and Electric Power, Zhengzhou, Henan 450045, China


Abstract
Seepage induced internal erosion in earth dams, dikes, and their underlying soil strata may cause destruction of earthen structures and flooding of lowland regions. In this study, efforts were made to evaluate the use of the enzyme induced carbonate precipitation (EICP) method for the control of internal erosion under water seepage. Gap-graded soils with 15% fine particles were improved by the EICP method for 1 to 5 passes. In each pass of treatment, 1.5 pore volume treatment liquid containing soybean-derived urease and 0.5 mol/L equimolar urea-calcium chloride was applied to the soil sample. After the EICP improvement, the soil samples underwent seepage erosion of stepwise-increased flow rates. In addition to the EICP-treated soil samples, an untreated soil sample and a soil sample treated by the microbially induced carbonate precipitation (MICP) method were also tested for comparison. The results showed that, in terms of the amount and rate of eroded fine particles, the EICP soil samples had stronger resistance against seepage erosion as compared with the MICP sample and the untreated soil sample. The erosion control effects also improved with treatment passes. The EICP improvement was also effective in reducing the axial deformation of soil. The level of axial deformation was roughly consistent with the amount of fine particles eroded. The calcium carbonate distribution was relatively uniform in the EICP samples compared with the MICP sample. The results presented in the paper show that the EICP method is a promising solution for the control of seepage induced internal erosion in soils.

Key Words
biocement; enzyme induced carbonate precipitation; internal erosion; soil improvement

Address
Jia He, Changhang Fang, Lei Hang, Yongshuai Qi, Xunyu Mao, Boyang Yan, Yundong Zhou and Yufeng Gao: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, China

Abstract
The improvement of expansive soils has crucial academic research significance and engineering application value. The regular practice using chemical improvement methods may be helpful to improve the expansive soil; however, at the cost of inconvenient material acquisition, troublesome mixing methods, expensive construction, and polluting the soil environment. To this end, based on the microbial induced calcium carbonate precipitation (MICP) technology, we carry out a series of soil modification tests on the expansive soil for the roadbed filling in Nanning, Guangxi. Considering the problematic behaviors of the expansive soil and its significant adverse effect on engineering, this paper focuses on the soil improvement; particularly, we aim to study the improved soil's physical properties, limit moisture content and swelling and shrinkage rates under the action of dry and wet cycles. It is found that the swelling index of the improved expansive soil has been decreased significantly, the free expansion rate drops to 14.9%, such that the samples fall into the category of non-expansive soil. The liquid limit and plastic limit of soil samples decreased to 47.2% and 20.4%, respectively, after 6 times of microbial treatment. Moreover, after several high-pressure consolidation tests under dry-wet cycle conditions, the hydrophilic capacity of the improved expansive soil is significantly weakened, and its corresponding water absorption induced swelling rate and drainage-induced shrinkage rate are significantly reduced. The above research results show that it is feasible to use the MICP technology to improve the swelling and shrinkage characteristics of the expansive soil; in particular, after six treatments with the microbial solution, all indices of the expansive soil achieve the best improvement effect.

Key Words
dry and wet cycles; fill expansive soil; MICP; swelling and shrinkage indices

Address
Weichang Jiang: 1.)Institute of Geotechnical Engineering, Central South University of Forestry and Technology, Changsha 410004, China
2.) Sinohydro Foundation Engineering Co., Ltd, Tianjin, 301700, China

Chunshun Zhang: Department of Civil Engineering, Monash University, Clayton, VIC, 3168, Australia

Hongbin Xiao, Shenping Luo, Zixiang Li and Xiaobing Li: Institute of Geotechnical Engineering, Central South University of Forestry and Technology, Changsha 410004, China

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