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CONTENTS
Volume 31, Number 1, October10 2022
 


Abstract
Urban deep excavation will affect greatly on the deformation of adjacent existing buildings, especially those with shallow foundations. Isolation piles has been widely used in engineering to control the deformation of buildings adjacent to the excavation, but its applicability is still controversial. Based on a typical engineering, numerical calculation models were established and verified through monitoring data to study the influence characteristics of isolation piles on the deformation of existing shallow foundation buildings. Results reveal that adjacent buildings will increase building settlement sv and the deformation of diaphragm walls sh, while the isolation piles can effectively decrease these. The surface settlement curve is changed from "groove" type to "double groove" type. Sufficiently long isolation pile can effectively decrease sv, while short isolation piles will lead to a negative effect. When the building is within the range of the maximum settlement location P, maximum building rotation om will increase with the pile length L and the relative position between isolation pile and building d/D increase (d is the distance between piles and diaphragm walls, D is the distance between buildings and diaphragm walls), instead, om will decrease for buildings outside the location P, and the optimum was obtained when d/D=0.7.

Key Words
deep excavation; deformation characteristics; existing buildings; isolation pile; numerical simulation

Address
Xinrong Liu, Peng Liu, Xiaohan Zhou, Linfeng Wang, Zuliang Zhong and Jilu Zhang: College of Civil Engineering, Chongqing University, Chongqing 400045, China
Xihui Lou and Tao Chen: China Railway Major Bridge Reconnaissance & Design Institute Co., Ltd., Wuhan Hubei 430050, China

Abstract
Slope stability during the excavation of twin road tunnels is considered crucial in terms of safety. In this research, physical model testing and numerical analysis were used to investigate the characteristics of the settlement (uz) and vertical stresses (oz) along the two tunnel sections. First, two model tests for a (fill-rock) slope were conducted to study the settlement and stresses in presence and absence of slope support (plate support system). The law and value of the result were then validated by using a numerical model (FEM) based on the physical model. In addition, a finite element model with a slope supported by piles (equivalent to the plate) was used for comparison purposes. In the physical model, several rows of plates have been added to demonstrate the capacity of these plates to sustain the slope by comparing excavating twin tunnels in supported and unsupported slope, the results show that this support was effective in the upper part of the slope, while in the middle and lower part the support was limited. Additionally, the plates appear to induce less settlement in several areas of the slope with differing settlement and stress distribution as compared to piles. Furthermore, as a results of the previous mentioned investigation, there are many factors influence the stress and settlement distribution, such as the slope' s cover depth, movement during excavation, buried structures such as the tunnel lining, plates or piles, and the interaction between all of these components.

Key Words
model test; numerical simulation; plates; slope stability; twin tunnels

Address
Xinrong Liu, Lojain Suliman, Xiaohan Zhou, Jilu Zhang, Bin Xu and Fei Xiong: College of Civil Engineering, Chongqing University, Chongqing 400045, China;
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China;
National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas (Chongqing), Chongqing 400045, China
Ahmed Abd Elmageed: National Authorities for Tunnels, Egypt

Abstract
Investigating and evaluating the long-term creep behavior of historical buildings built on seismic zones is of great importance in terms of transferring these structures to future generations. Furthermore, assessing the earthquake behavior of historical structures such as masonry stone bridges is very important for the future and seismic safety of these structures. For this reason, in this study, earthquake analyses of a masonry stone bridge are carried out considering strong ground motions and various water levels. Tokatli masonry stone arch bridge that was built in the 10th century in Turkey-Karabük is selected for three-dimensional (3D) finite difference analyses and this bridge is modeled using FLAC3D software based on the three-dimensional finite difference method. Firstly, each stone element of the bridge is modeled separately and special stiffness parameters are defined between each stone element. Thanks to these parameters, the interaction conditions between each stone element are provided. Then, the Burger-Creep and Drucker-Prager material models are defined to arch material, rockfill material for evaluating the creep and seismic failure behaviors of the bridge. Besides, the boundaries of the 3D model of the bridge are modeled by considering the free-field and quiet boundary conditions, which were not considered in the past for the seismic behavior of masonry bridges. The bridge is analyzed for 6 different water levels and these water levels are 0 m, 30 m, 60 m, 70 m, 80 m, and 90 m, respectively. A total of 10 different seismic analyzes are performed and according to the seismic analysis results, it is concluded that historical stone bridges exhibit different seismic behaviors under different water levels. Moreover, it is openly seen that the water level is of great importance in terms of earthquake safety of historical stone bridges built in earthquake zones. For this reason, it is strongly recommended to consider the water levels while strengthening and analyzing the historical stone bridges.

Key Words
burger-creep material model; earthquake analysis; free-field boundary condition; masonry arch bridge; water level

Address
Murat Cavuslu: Department of Civil Engineering, Zonguldak Bulent Ecevit University, Zonguldak, Türkiye

Abstract
In densely built areas, the development of underground transportation systems often involves twin excavations, which are sometimes unavoidably constructed adjacent to existing piled foundations. Because soil stiffness degrades with induced stress release and shear strain during excavation, it is vital to investigate the piled raft responses to subsequent excavation after the first tunnel in a twin-excavation system. The effects of deep excavations on existing piled foundations have been extensively investigated, but the influence of twin excavations on a piled raft is seldom reported in the literature. In this study, three-dimensional numerical analyses were carried out to investigate the influence of sand density on an existing piled raft (with a working load on top of the raft) due to twin excavations. A wide range of relative density (Dr) from loosest (30%), loose to medium (50% and 70%), and densest (90%) were selected to investigate the effects on settlement and load transfer mechanism of the piled raft during twin excavations. An advanced hypoplastic sand model (which can capture small-strain stiffness and stress-state dependent dilatancy of sand) was adopted. The model parameters are calibrated against centrifuge test results in sand reported in the literature. From the computed results, it is found that twin excavations in loose sand (Dr=30%) caused the most significant settlement. This is because of the higher stiffness of denser sand (Dr=90%) than that of loose sand. In contrast, a much larger tilting (maximum magnitude=0.18%) was computed in dense sand than in loose sand after the completion of the first excavation. As far as the load transfer mechanism along the piles is concerned, an upward load transfer to mobilize shaft resistance is observed in loose sand. On the contrary, a downward load transfer is observed in dense sand.

Key Words
load transfer; piled raft; sand density; tilting; twin excavations

Address
Hemu Karira and Tauha Hussain Ali: Department of Civil Engineering, Mehran University of Engineering and Technology, Shaheed Zulfiqar Ali Bhutto Campus,
Khairpur Mir's, Sindh, Pakistan
Aneel Kumar and Tauha Hussain Ali: Department of Civil Engineering, Mehran University of Engineering and Technology, Jamshoro, Sindh, Pakistan
Li Yaun: School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, P.R. China

Abstract
In Taiwan, an efficient approach for enhancing the stability of colluvium slopes is the drilled shaft method. For slopes with drilled shafts, the soil arching effect is one of the primary factors influencing slope stability and intertwines to the failure mechanism of the pile-soil system. In this study, the contribution of soil arching effect to slope stability is evaluated using the FEM software (Plaxis 3D) with the built-in strength reduction technique. The result indicates the depth of the failure surface is influenced by the S/D ratio (the distance to the diameter of piles), which can reflect the contribution of the soil arching effect to soil stability. When a (rock inclination angles)=B (slope angles) is considered and the S/D ratio=4, the failure surface of the slope is not significantly influenced by the piles. Overall, the soil arching effect is more significant on a=b, especially for the steep slopes. Additionally, the soil arching effect has been included in the proposed stability charts. The proposed charts were validated through two case studies, including that of the well-known Woo-Wan-Chai field in Taiwan. The differences in safety factor (FoS) values between the referenced literature and this study was approximately 4.9%.

Key Words
colluvium; drilled shaft; failure mechanism; soil arching effect; stability charts

Address
An-Jui Li, Wei-Chien Wang and Horn-Da Lin: Department of Civil and Construction Engineering, National Taiwan University of Science and Technology,
No.43, Keelung Rd., Sec.4, Da'an Dist., Taipei City, Taiwan R.O.C.

Abstract
The excessive settlement and deformation of disintegrated carbonaceous mudstone (DCM) embankments under dynamic loading have long been problems for engineers and technicians. In this work, the characteristics and mechanism of the plastic deformation of DCM under different degrees of compaction, water contents and confining pressures were studied by static triaxial, dynamic triaxial and scanning electron microscopy testing. The research results show that the axial stress increases with increasing confining pressure and degree of compaction and decreases with increasing water content when DCM failure. The axial strain at failure of the DCM decreases with increasing confining pressure and degree of compaction and increases with increasing water content. Under cyclic dynamic stress, the change in the axial stress level of the DCM can be divided into four stages: the stable stage, transition stage, safety reserve stage and unstable stage, respectively. The effects of compaction, water content and confining pressure on the critical axial stress level which means shakedown of the DCM are similar. However, an increase in confining pressure reduces the effects of compaction and water content on the critical axial stress level. The main deformation of DCM is fatigue cracking. Based on the allowable critical axial stress, a method for embankment deformation control was proposed. This method can determine the degree of compaction and fill range of the embankment fill material according to the equilibrium moisture content of the DCM embankment.

Key Words
carbonaceous mudstone; critical axial stress level; cyclic dynamic stress; embankment deformation control; plastic deformation

Address
Xiang Qiu, Yixiang Yin, Sini Fu and Jinhong: Department of Civil Engineering, Changsha University of Science & Technology,No. 950, Section 2, Wanjiali South Road, Tianxin District, Changsha City, Hunan Province, China
Huangbin Jiang: Department of Traffic & Transportation Engineering, Changsha University of Science & Technology,
No. 950, Section 2, Wanjiali South Road, Tianxin District, Changsha City, Hunan Province, China

Abstract
The present study examines the natural frequencies (NFs) of perfect/imperfect functionally graded sandwich beams (P/IP-FGSBs), which are composed of a porous core constructed of functionally graded materials (FGMs) and a homogenous isotropic metal and ceramic face sheets resting on elastic foundations. To accomplish this, the material properties of the FGSBs are assumed to vary continuously along the thickness direction as a function of the volume fraction of constituents expressed by the modified rule of the mixture, which includes porosity volume fraction represented using four distinct types of porosity distribution models. Additionally, to characterize the reaction of the two-parameter elastic foundation to the Perfect/Imperfect (P/IP) FGSBs, the medium is assumed to be linear, homogeneous, and isotropic, and it is described using the Winkler-Pasternak model. Furthermore, the kinematic relationship of the P/IP-FGSBs resting on the Winkler-Pasternak elastic foundations (WPEFs) is described using trigonometric shear deformation theory (TrSDT), and the equations of motion are constructed using Hamilton' principle. A closed-form solution is developed for the free vibration analysis of P/IP-FGSBs resting on the WPEFs under four distinct boundary conditions (BCs). To validate the new formulation, extensive comparisons with existing data are made. A detailed investigation is carried out for the effects of the foundation coefficients, mode numbers (MNs), porosity volume fraction, power-law index, span to depth ratio, porosity distribution patterns (PDPs), skin core skin thickness ratios (SCSTR), and BCs on the values of the NFs of the P/IP-FGSBs.

Key Words
boundary conditions; FGMs; free vibration; porosity; sandwich beams; Winkler-Pasternak elastic foundations

Address
Mehmet Avcar and Recep Akan: Department of Civil Engineering, Faculty of Engineering, Suleyman Demirel University, Cunur, Isparta, Türkiye
Lazreg Hadji: Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam;
Department of Civil Engineering, University of Tiaret, BP 78 Zaaroura, Tiaret, 14000, Algeria;
Laboratory of Geomatics and Sustainable Development, University of Tiaret, 14000, Algeria

Abstract
The undrained shear strength of soil is considered one of the engineering parameters of utmost significance in geotechnical design methods. In-situ experiments like cone penetration tests (𝐶𝑃𝑇) have been used in the last several years to estimate the undrained shear strength depending on the characteristics of the soil. Nevertheless, the majority of these techniques rely on correlation presumptions, which may lead to uneven accuracy. This research' general aim is to extend a new united soft computing model, which is a combination of random forest (𝑅𝐹) with grasshopper optimization algorithm (𝐺𝑂𝐴) to the pile set-up parameters better approximation from 𝐶𝑃𝑇, based on two different types of data as inputs. Data type 1 contains pile parameters, and data type 2 consists of soil properties. The contribution of this article is that hybrid 𝐺𝑂𝐴−𝑅𝐹 for the first time, was suggested to forecast the pile set-up parameter from 𝐶𝑃𝑇. In order to do this, CPT data and related bore log data were gathered from 70 various locations across Louisiana. With an 𝑅2 greater than 0.9098, which denotes the permissible relationship between measured and anticipated values, the results demonstrated that both models perform well in forecasting the set-up parameter. It is comprehensible that, in the training and testing step, the model with data type 2 has finer capability than the model using data type 1, with 𝑅2 and 𝑅𝑀𝑆𝐸 are 0.9272 and 0.0305 for the training step and 0.9182 and 0.0415 for the testing step. All in all, the models results depict that the A parameter could be forecasted with adequate precision from the 𝐶𝑃𝑇 data with the usage of hybrid 𝐺𝑂𝐴−𝑅𝐹 models. However, the 𝑅𝐹 model with soil features as input parameters results in a finer commentary of pile set-up parameters.

Key Words
cone penetration test; grasshopper optimization algorithm; pile parameters; pile set-up parameter A; random forest model; soil properties

Address
Zhilong Zhao, Simin Chen, Dengke Zhang, Bin Peng and Xuyang Li: Shaanxi Construction of Land Comprehensive Development Co. Ltd, Xi'an Shanxi, 710000, China
Qian Zheng: Faculty of Civil Engineering, UAE Branch, Islamic Azad University, Dubai, 502321, UAE


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