Influence of Isosceles Trapezoid Cross-section on the Reinforcement Effect of Stabilizing Piles

Changdong Li,Xinwang Liu,Qingtao Liu,Tao Liu 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.7

The paper conducts the study on the influence of isosceles trapezoid cross section on the reinforcement effect of stabilizing piles by employing the numerical modeling approach. On the basis of soil arching theory with end-bearing soil arching and friction soil arching, the modified mechanical model for the arbitrary isosceles trapezoid cross-section piles was proposed. The impacts of different slope ratios of the sidewall of the isosceles trapezoid cross-section piles on the displacement and load sharing of driving force were examined utilizing the explicit finite-difference software FLAC3D. The result of displacement contour graphs indicates that the stabilizing piles with trapezoid cross-section are better capable of resisting the deformation under the action of driving force. The logarithmic function between the load sharing percentage of end-bearing soil arching and slope ratio, and power function between the load sharing percentage of the friction soil arching and slope ratio were established for inner isosceles trapezoid crosssection piles. Similarly, the power function between the load sharing percentage of end-bearing soil arching and slope ratio was proposed for outer isosceles trapezoid cross-section piles. Furthermore, the reaction of soil arching on the stabilizing piles in view of the stress distribution discipline around piles was investigated. The result shows that the maximum vertical stress occurs in the back corners of stabilizing piles; consequently, the strength and rigidity of the back corners of stabilizing piles should be strengthened to resist the concentrated stress.

Optimal Location of Piles in Stabilizing Slopes Based on a Simplified Double-row Piles Model

Changdong Li,Wenqiang Chen,Yingjie Song,Wenping Gong,Qihua Zhao 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.2

Embedding single-row piles is often adopted to stabilize slopes in engineering practice. However, for large-scale and complex slopes, single-row piles might not be able to stabilize the slope; rather, double-row piles, even multirow piles, should be adopted. Currently, the optimal locations of double-row stabilizing piles considering local instability of the slope have rarely been studied. In this paper, a simplified analytical model used to analyze double-row pile stabilized slopes is proposed, where the local failure of the slope above the first row of piles is considered. Through the kinematic approach of limit analysis combined with the strength reduction technique, the required resistance forces provided by double-row piles respectively are derived for different pile locations denoted by the rotational angle. Moreover, a framework is developed for analyzing the optimal locations of multirow piles considering multistage potential slip surfaces. The results of an illustrative example are presented, and the reasonableness of the proposed method is verified. It is concluded that the optimal locations of double-row piles lie within middle-lower part of the corresponding stabilized part of the slope. Finally, discussion illustrates the influences of the seismic effects and soil shear strength parameters on the derived optimal pile locations. This study provides novel scientific insight into the optimized design of stabilizing pile locations in engineering practice.

Numerical Modelling Study of the Load Sharing Law of Anti-sliding Piles based on the Soil Arching Effect for Erliban Landslide, China

Changdong Li,Huiming Tang,Xinli Hu,Liangqing Wang 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.6

This paper presents a new model of the load sharing law with a three-stage load sharing pattern via a representative case study in the Three Gorges reservoir region, China. A definitive new three-stage load transfer pattern is presented, including end-bearing soil arching, friction soil arching and the sliding mass in front of the pile. By means of the soil arching effect between the anti-sliding pile and landslide mass, the law of the load sharing ratio under different cases, including different intervals, section dimensions, driving forces, and shearing parameters of the sliding mass and the pile-soil interface, is presented by using the explicit finite-difference numerical modelling method. The results show that (a) the effect scale of the soil arching effect is within the scale of four times of the width of the pile; (b) the soil arching only exits within a certain pile interval, and it will become inefficiency beyond the maximum pile interval; (c) there is a threshold value for the cohesion strength parameters of the sliding mass, beyond which the load sharing ratios of soil arching keep in a steady level.

Application of Self-organizing Mapping-Random Forest Model to Map Landslide Susceptibility in Zigui Basin, Three Gorges Reservoir Region, China

( Changdong Li ),( Jingjing Long ),( Zhiyong Fu ),( Wenqiang Chen ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

The Zigui basin is one of the most landslide-prone areas where thousands of landslides are distributed. Researches show that areas sharing the same conditions as identified landslides are clearly potential areas for future disasters. Performing the landslide susceptibility mapping is a heated issue in the area. Continued improvements in high-resolution satellite images, and the developments of unmanned aerial vehicles (UAVs) and site-investigation function well in constructing effective, high-quality landslide databases. GIS technology and machine learning algorithms have been widely applied in landslide susceptibility prediction. Whereas, whether the random and subjective selection of the landslides or non-landslides grid cells are reasonable in research of landslide susceptibility mapping is the existence problem. Based on the Two step cluster (TSC) algorithm and the Self-organizing mapping - Random forest (SOM-RF) model, a novel hybrid model is proposed to overcome the above drawbacks. SOM is used to produce a preliminary landslide susceptibility mapping. TSC algorithm is applied in telling apart the most reasonable True-Positive (TP) from recorded landslide grid cells in high-susceptibility zones and the False-Positive (FP) in low-susceptibility zones. Afterwards, the labeled datasets are imported into the RF model for training. And then the trained SOM-RF model is utilized to perform an improved landslide susceptibility mapping. Most areas with high or very high susceptibility are located within the hydro-fluctuation belt of the TGR. Compared with the susceptibility mapping produced by single RF model, the results of SOM-RF model demonstrate to have the superior prediction skill and higher reliability.

Orders-of-magnitude enhancement in conductivity tuning in InGaZnO thin-film transistors via SiNx passivation and dual-gate modulation

ChangDong Chen,ChenNing Liu,JiWen Zheng,GongTan Li,Shan Li,QianWu,JinWu,Chuan Liu 한국정보디스플레이학회 2019 Journal of information display Vol.20 No.3

The mobility of pristine amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) is insufficient to meet the requirement of the future ultra-high-definition displays. Reported herein is the fabrication of hydrogenated long-channel IGZO TFTs exhibiting a transconductance and an on/off ratio that are orders of magnitude superior to those of the regular devices. The gate bias stability of the treated IGZO TFTs was greatly enhanced, with the threshold voltage shifting by less than 1 V after 1 h stress. Experimentally, the hydrogenation of the active layer was achieved via the deposition of a SiNx/SiOx bilayer on top of the IGZO via plasma-enhanced chemical vapor deposition followed by post-annealing under optimized conditions. The elemental depth profiles indicated that this enhanced performance originated from the hydrogen doping of the IGZO film. Furthermore, a dual-gate structure was fabricated to alleviate the deterioration of the subthreshold properties induced by the excess hydrogen doping.

Restoring force model for circular RC columns strengthened by pre-stressed CFRP strips

Changdong Zhou,Xilin Lu,Hui Li,Teng Tian 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.17 No.4

This paper presents a tri-linear restoring force model based on the test results of 12 circular RC columns strengthened by CFRP strips under low cyclic loading. The pre-stress of CFRP strips and axial load ratio of specimens are considered as the affect parameters of the proposed model. All essential characteristics of the hysteretic behavior of the proposed model, including the hysteretic rules, main performance points, strength degradation, stiffness degradation and confinement effects are explicitly analyzed. The calculated results from the proposed model are in good agreement with the experimental results, which shows that the recommended model can be reliably used for seismic behavior predictions of circular RC columns strengthened by pre-stressed CFRP strips.

A Novel Approach for Determining Pile Spacing considering Interactions among Multilayered Sliding Masses in Colluvial Landslides

Haikuan Zhang,Changdong Li,Wenmin Yao,Jingjing Long 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.9

It is reported that there are many colluvial landslides with multilayered sliding masses; however, previous studies of the pile spacing of stabilizing piles mainly focus on the single-layered sliding mass, which may lead to design errors for pile spacing. Consequently, the paper presents a novel method to determine the pile spacing with considering interactions of multilayered sliding masses in colluvial landslides. Based on a generalized landslide model, equations for calculating stability coefficients of multilayered sliding masses were improved by examining the interactions among sliding masses. An accordingly colluvial landslide model with double-layered sliding masses was established by the finite differential method. The distribution of vertical landslide driving force and horizontal loading between adjacent piles were studied based on the colluvial landslide. A novel method of calculating the maximum pile spacing and minimum pile spacing was deduced by considering the soil arching effect and the interactions among multilayered sliding masses. The reasonable pile spacing was obtained considering cost and performance of stabilizing piles. The calculational process, which determines optimal pile spacing in multilayered masses, were shown based on the Bazimen landslide. The variations in pile spacing affected by various soil-layer sequences was illustrated by employing the Bazimen landslide model. The calculation results indicate that the pile spacing is positively correlated with the depth of soil with the maximum resistance sliding force. Effectiveness and significance of the presented method were proved through verify the calculational results by using numerical modeling approaches.

Optimal Isosceles Trapezoid Cross Section of Laterally Loaded Piles based on Friction Soil Arching

Junjie Wu,Changdong Li,Qingtao Liu,Fusong Fan 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.7

The paper presents a novel analytical solution to determine an optimal isosceles trapezoid cross-section of stabilizing piles subjected to the lateral load. In view of the pile-soil interaction mechanical analysis on the friction soil arching between the adjacent stabilizing piles, a general mechanical model for analyzing the behavior of the laterally loaded stabilizing piles with isosceles trapezoid cross-section is put forward. The reasonable net pile spacing expression for all kinds of isosceles trapezoid section piles is established via the analytical deduction, and it indicates that there is a positive relationship between the reasonable net pile spacing and gradient of pile sidewall. In consideration of the strength failure possibility in the apex of friction soil arching, the complete expressions of both the gradient of pile sidewall and corresponding reasonable net pile spacing of stabilizing piles can be established. The case study of Jinle landslide verifies that the reasonable pile spacing obtained by the presented model is slightly greater than that of the conventional design scheme, which shows that the stabilizing piles with optimal isosceles trapezoid cross-section can results in reducing the investment of the whole stabilizing piles.

Component Prototyping for the China Spallation Neutron Source Project

Jie Wei,Yanwei Chen,Yunlong Chi,Changdong Deng,Haiyi Dong,Shinian Fu,Wei He,Kaixi Huang,Wen Kang,Jian Li,Huafu Ouyang,Huamin Qu,Caitu Shi,Hong Sun,Jingyu Tang,Juzhou Tao,Sheng Wang,Zhongxiong Xu,Xueju 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.5

The China Spallation Neutron Source (CSNS) complex consists of an H- linear accelerator, a rapid cycling synchrotron accelerating the beam to 1.6 GeV, a solid tungsten target station and instruments for spallation neutron applications. The facility operates at a 25-Hz repetition rate with an initial design beam power of 120 kW and is upgradeable to 500 kW. The primary challenge is to build a robust and reliable user-friendly facility with upgrade potential at a fraction of the \world standard" cost. Success of the project relies on the results of prototyping research & development (R&D) of key technical systems and components. This paper discusses the prototyping experiences of the past two and a half years. The China Spallation Neutron Source (CSNS) complex consists of an H- linear accelerator, a rapid cycling synchrotron accelerating the beam to 1.6 GeV, a solid tungsten target station and instruments for spallation neutron applications. The facility operates at a 25-Hz repetition rate with an initial design beam power of 120 kW and is upgradeable to 500 kW. The primary challenge is to build a robust and reliable user-friendly facility with upgrade potential at a fraction of the \world standard" cost. Success of the project relies on the results of prototyping research & development (R&D) of key technical systems and components. This paper discusses the prototyping experiences of the past two and a half years.