bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on Anti-abrasion Property of Waterborne Epoxy Mortar Based on Underwater Steel Ball Method
Authors: Yu Liang , Guo Jia-chen , Ma Yue , Zhang Lei
Published: September 2019

Waterborne epoxy emulsion modified mortar has been paid more and more attention and applied in the field of hydraulic construction. Its physical and mechanical properties, especially the anti-erosion properties, are the key influencing parameters applied to the drainage structures such as sand tunnel and spillway dam surface. A high-speed underwater steel ball punching tester was used to simulate the impact of pushing mass on the abrasion resistance of water-borne epoxy mortar. In this paper, the abrasion resistance of mortar under different rotational speeds and different grades of grinding steel balls are analyzed, and the test parameters of underwater steel ball method suitable for waterborne epoxy mortar are explored, then a method for predicting the punching and grinding life of mortar is well proposed. The research results provide a basis for the application of water-borne epoxy mortar to hydraulic structures required by anti-impact abrasion.
Seismic Behaviors on CFGRD
Authors: Yan Qian , Wu Di , Wang You-bo , Wang Ya-jun , Gan Xiao-qing , Dong Zhi-hong
Published: September 2019

The goal structure is the concrete-faced grouted rockfill dam (CFGRD) in Zhoushan of China. Based on the properties non-linearity, the structural interaction and the seismic uncertainty, the dynamic non-linear constitutive model has been established in order to evaluate the seismic safety of the CFGRD as well as its interactive zones. Their dynamic sensibility has also been explored with the dynamic FEM. According to the results of the comprehensive dynamic response field distributions, the rock-bolts family of the CFGRD plays the principal role for the seismic safety.
Two-dimensional dynamic analysis of seismic slope stability using DEM coupling with strength reduction technique
Authors: Wu Weidong , Zhang Fei , Hu Kangjun , Ye Min , Ge Bin
Published: September 2019

The seismic stability of earth slopes attracts more attentions. In this study, the two-dimensional dynamic analyses of slope stability subjected to earthquakes are conducted by DEM. In order to prevent boundary effect in dynamic analysis, the quiet boundary is applied in the model, which can fully absorb seismic waves. The progressive failures are clearly observed. The obtained slip surface is in good agreement with that determined by pseudo-static method. In order to calculate the factor of safety using DEM, the strength reduction technique is adopted. A numerical example regarding the instability of the soil slope induced by earthquake shows the validation of the strength reduction technique. In the procedure, several failure criteria are proposed to determine the global instability of the slope. The factor of safety is defined and then compared with the results from other methods. It demonstrates that the discrete element method with strength reduction technique is a promising and feasible method for assess the seismic slope stability.
Assessing the Stability of Poor Drainage Soil Slopes Under the Combined Effect of Water Level Drawdown and Rainfall
Authors: Tang Libin , Wang Ling , Zhang Wengang
Published: September 2019

In rainy season, the reservoir water level sometimes decreases greatly for the requirement of flood discharge. Such phenomenon may cause severe landslides for poor drainage soil slopes. Therefore, it’s necessary to assess the slope stability under the combined effect of rainfall and water level drawdown. In this study, a homogeneous soil slope was modelled to investigate the relative importance and failure mechanism of water level drawdown and rainfall. Both the “factor of safety” (FOS) and the “probability of failure” (POF) were computed in the analysis. The numerical results show that landslides are more susceptible to water level drawdown, while rainfall is a secondary influence to poor drainage soil slopes, subjected to the combined effect of water level drawdown and rainfall.
Analysis on Early Warning Capability of Gansu Earthquake Early Warning Stations Network
Authors: Pan Zhangrong , Tian Xiufeng , Zhang Weidong , Yuan Jie
Published: September 2019

This paper briefly introduces the structure and network layout of Gansu Earthquake Early Warning Stations Network, and discusses the relationship of the effective early warning time and the radius of early warning blind zone with consumed time for early warning. Based on the layout of the current and future earthquake early warning stations network of Gansu, the consumed time for early warning under three stations triggered and six stations triggered is calculated and analyzed. In addition, the contour map of consumed time for early warning in Gansu is drawn. The results show that the effective early warning time is negatively correlated with consumed time for early warning, and the radius of the early warning blind zone is positively correlated with consumed time. And the consumed time for early warning of the future earthquake early warning stations network under three triggered stations and six triggered stations in Gansu is shortened by 29.24% and 37.13% compared with those of the current earthquake early warning stations network. After the completion of the Gansu Subproject, the effective early warning time will be increased and the radius of the early warning blind zone will be reduced, then the early warning capability in Gansu is to be greatly improved.
Experimental Study on Shear Strength of Geomembrane Welding Seams under Different Inflation Time and Pressure
Authors: Zhizhou Geng , Chengfeng Zheng , Kai Xu
Published: September 2019

The shear strength of geomembrane welding seams (GWSs) is one of the key factors for the reliability of geotechnical anti-seepage system. In order to study the evolution law of shear strength of GWSs under different inflation time and pressure, the weld shear strength tests of seven different thicknesses of HDPE geomembrane were carried out under different inflation time and pressure conditions. The test results show that the weld shear strength increases with the increasing geomembrane thickness under the same inflation time (3min or 10min) or the same test inflation pressure (0.1MPa or 0.2MPa). Additionally, the trend of all test curves is similar. The hot-welding method shows good stability in weld shear strength of different thicknesses of HDPE geomembrane. The shear strength values of GWSs of the same thickness under different inflation pressures and inflation times are similar. During the shearing process of the welds, the weakened area of the material at the joint between the edge of the weld and the geomembrane base material is most likely to be destroyed. The corresponding test results can provide reference for GWS inspection and related engineering.
Experimental and Numerical Study on Impact Behavior of Welded Hollow Sphere Joint under Continuous Impact Load
Authors: Wu Chang , Huang Guiwu , Ding Jinwei
Published: September 2019

In order to analyse the influence of continuous impact load and the stiffness of the welded hollow sphere joints on the impact resistance of the welded hollow sphere joints and verify the reliability of the generalized finite element software ANSYS/LS-DYNA precise modeling analysis of impact problems, two sets of the welded hollow sphere joints models with diameters of 80mm and 100mm were designed. The experimental results of three deformation stages (elastic, elastic-plastic and plastic deformation stages) in 18 working conditions of the two groups of models were analyzed. From the deformation mode, the acceleration and displacement of the sphere joint, the strain of the model member and the finite element simulation results, it is found that the test results and the finite element simulation are highly consistent. At the same time, the results show that the higher the stiffness of the welded hollow sphere joints, the better impact resistance of the joints. The continuity of the load has a great weakening effect on the impact resistance of the elastic-plastic and plastic deformation stages of the joints.
Study on Compressive Performance and Safety Assessment of Stone Masonry Structure in Tibet
Authors: Teng Dong-yu , Na Yang
Published: September 2019

Tibetan stone masonry is different from common masonry structure. However, currently, few studies on its structural characteristics and mechanical properties are conducted. This paper summarizes the materials, composition and masonry methods of Tibetan stone masonry, and analyzes its structural characteristics. A uniaxial compression test on the small specimens built in the laboratory and the full-scale wall specimens on the site is conducted to explore the damage mechanism of the Tibetan stone masonry. Based on the compression performance of Tibetan stone masonry, this paper proposes the factor set, weight coefficient, and rating criteria of the safety assessment of the Tibetan stone masonry components by using the fuzzy comprehensive evaluation and analytic hierarchy method. The evaluation method of the safety status of components is also put forward, which is validated by the test results.
The Assessment of The Integrated Structural Flood Control System in The Jingjiang Reach of The Yangtze River on Mitigating a Catastrophic Flood
Authors: Xu Xingya , Zhang Liming , Xu Zhaoming
Published: September 2019

In order to mitigate the flood disaster, an integrated structural flood control system, mainly incorporating levees, reservoirs, and flood diversion and detention zones, has been established in the JingJiang Reach of the Yangtze River by the efforts of Chinese government after several decades. The flood control effect of the integrated structural flood control system on mitigating the most catastrophic flood in history record which did occur in 1870 was assessed. According to the results, the used storage for flood control of the Three Gorges Reservoir is 18.4 billion m3 and the used storage for flood control of the other upstream reservoirs is 9.3 billion m3. The used flood storage of the Jingjiang Flood Diversion Zone is 5.4 billion m3 and the highest water level at Shashi Station is 45.00m. It shows that the flood control safety in the Jingjiang Reach is ensured to reach the achievement that controlling the highest water level at Shashi Station no more than 45.00m in the flood of 1870 to avoid the likely catastrophic flood disaster in the Jianghan plain and Dongting Lake plain along the Jingjiang Reach.
Safety Assessment Technology of Concrete Gravity Dams
Authors: Zhang Jiahong , Li You , Li Xiulin
Published: September 2019

Most reservoir dams in China were built before the 80s of last century, the issue of long-term security had become increasingly prominent. In recent years, with the “high dam, large reservoir, long water diversion” water conservancy project overall construction, safety assessment of some major water conservancy projects will become a major problem for a long time. Taking some gravity dam as an example, this paper introduced and summarized the safety assessment technology of concrete gravity dam, which would provide reference for safety evaluation and technical development of concrete dam in the future.
Research on the Model Test of the Debris Landslide’s Evolution Process in Tailings Reservoir
Authors: Qi Qinglan , Zhang Liting , Wang Xiaogang , Zhang Shaoxiong , Wu Yongqing
Published: September 2019

Based on the actual tailings reservoir project, a model test study on the evolution pattern of dam-breaking debris landslide is carried out. According to the similarity criterion of water flow and mud-sand movement, coal dust satisfying the similar relationship is selected as model sand. By analyzing the dam-breaking debris landslide’s range, propulsion speed, submerged depth distribution and particle deposition characteristics, the movement pattern of the landslide is obtained. In the short time after the dam break, the submergence range and advancing speed of the debris landslide increase rapidly. During the propulsion process, due to the increase of the debris landslide in the downstream of the valley, the debris landslide is diffused and the energy consumption during the flow is made. The advancing speed decrease until the landslide stops; The final submerged depth distribution of the dam breach has obvious randomness and non-uniformity, which is mainly related to the downstream terrain; According to the particle size grading analysis of the soil sample at the characteristic location, the further away from the dam toe, the finer particle content in the debris landslide.
Seismic damage analysis and reinforcement measure research for earth dams after a strong earthquake
Authors: Yang Baoquan , Ma Zhifa , Guo Xuyuan , Chen Yuan , Zhang Lin , Chen Jianye
Published: September 2019

At present, there are more than 98,000 reservoirs and dams in China. Most of these projects are earth dams. As unexpected disasters and events occur frequently, emergency response problems facing reservoirs and dams are increasingly prominent. Especially during a strong earthquake, the dangerous problems of these dams will be more serious, which is a serious threat to people’s lives and property downstream. Therefore, the seismic damages and the measures of reinforcement need to be studied. Basic data of 379 reservoirs were at high-risk or at dam-break risk, as well as the damage situations of medium and small earth dams damaged in the Wenchuan earthquake, are collected and presented in this paper. Several main failure modes of earth dams during the earthquake are analyzed and summarized. For practical engineering, some reinforcement measures for the typical failure mode of an earth dam are also proposed. The Wenjiajiao earth dam, a typical medium reservoir in the high-risk category, located in Cangxi County, Sichuan Province, is selected as the analysis example. The dam safety and seismic stability are calculated and analyzed by the finite element software program ANSYS. The results indicate that the biggest permanent deformation caused by the earthquake occurred in the dam crest; the maximum deformation is mainly a downward subsidence of 21.8 cm. As the thickness of the dam top part decreases, the dynamic displacement and vibration velocity of the dam crest increases. This calculation is consistent with the actual situation where the parapet wall of a dam crest was seriously incline and the upper slope collapsed and cracked. The research results can provide a reference for the danger control and reinforcement of similar earthquake damaged reservoirs.
Nonlinear seismic finite element modeling method for super long span column tower cable-stayed bridge
Authors: Cheng Leike
Published: September 2019

This project takes Wuhu Yangtze River Highway Second Bridge as an engineering example. In view of the structural and seismic characteristics of the new structure such as the super-long-span sub-limb column tower cable-stayed bridge and the oblique damping system, the partial precision modeling is applied to the seismic vulnerable components such as sub-limb column tower and pier on the basis of the seismic finite element model of the space bar system. In addition, the correct and reasonable finite element simulations of the important components and seismic construction measures such as cables and oblique dampers, are carried out by adopting the elements and constitutive relationships suitable for structural seismic analysis. Meanwhile, the material nonlinearity and geometric nonlinearity of super-long span bridges can be considered and nonlinear seismic finite element model of super-long-span column cable-stayed bridges is established.
Influence of Seismic Relative Wavelength on Strain Transfer Rate of Cross-section of Underground Structure
Authors: Zhou Yubao , Shi Tao
Published: September 2019

The seismic response of underground structures in nonlinear foundations was analyzed by using FLAC 3D software, and the effect of relative wavelength on the transverse strain transfer rate of structures is studied. The variation processes of the strain transfer rate can be divided into three distinct phases. In the first stage where the relative wavelength raises from 0.2 to 1.0, the strain transfer rate increases almost linearly with it; while in the second stage where the relative wavelength increases from1.0 to 2.0, the growth trend is slowing down. And the strain transfer rate almost keeps a constant value during the last phase, in which stage the uniform strain field of soil can be used to analyze the strain transfer rate. According to the influence of relative wavelength and relative stiffness on the strain transfer rate, the calculation formula of the strain transfer rate is summarized.
Study on influence of dam foundation damage on seismic safety of gravity dam under combined action of main shock and aftershock
Authors: Zhang Liaojun , Zhai Yafei , Chen Dongsheng , Cui Xiao
Published: September 2019

The existing seismic design codes for hydraulic structures have not yet required to consider the impact of strong aftershocks on the secondary damage caused by the dam. However, the actual earthquake damage indicates that the impact of strong aftershocks cannot be ignored. In order to study the seismic safety of concrete gravity dam subjected to strong earthquakes, this paper constructs a constitutive model that reasonably reflects the dynamic damage evolution process of dam concrete based on damage mechanics theory. According to the similarity of concrete and rock material, the concrete damage model is extended to the rock mass material. Based on this, taking the gravity dam as an example, the overall damage mechanics model of the dam body and the dam foundation is established. According to the characteristics of the dam site and the characteristics of ground motion, the artificial seismic wave with time-frequency non-stationary characteristics is synthesized considering the attenuation law of ground motion duration and intensity envelope function. The effects of main shock and strong aftershock on the whole damage of gravity dam are studied. The results show that the strong aftershock after the main shock has different cumulative effects on the overall damage and plastic strain of the gravity dam. The gravity dam will further expand in the damaged area when subjected to strong aftershocks. The cumulative effect of the aftershock on the damage and plastic strain of the foundation is more significant than that of the dam. Therefore, it is necessary to consider the plastic damage of the dam and the dam foundation in the seismic analysis of the dam.
Analysis of dynamic characteristics and seismic performance for Shengshousi Pagoda
Authors: Cui Xiaoling , Fang Fei , Lu Junlong
Published: September 2019

To study the dynamic characteristics and seismic performance of the Shengshousi Pagoda, the present status preserved of the pagoda’s structure was investigated on site, and the numerical computation model was established based on the parameters determined by calculated value of the natural vibration frequency of the structure. The responses of acceleration, displacement, story drift and stress were analyzed under three-way seismic wave. The seismic performance of pagoda structure was evaluated according to the calculation results of displacement and stress, and the failure criterion of pagoda materials. The results indicate that the natural frequencies in the east-west are close to that in north-south. The response laws of acceleration, displacement and stress are similar under three-way seismic wave of 8-degree fortification earthquake. Under the frequent earthquakes, the structure of pagoda does not suffer from compression damage; the tensile damage area is located at the bottom floor. Under the fortification and rare earthquakes, significant compression damage area is located at lower floors of the ancient pagoda, the stress concentration occurs around the part of opening, and significant tensile damage occurs.
Study on the Rule of Concrete Corrosion in Harsh Environment
Authors: Zhang Liming , Li Jia , Yu Hongfa , Zhan Qinpeng
Published: September 2019

The surface corrosion of 3 type concrete beams in hostile environment is researched by measuring concrete beams surface corrosion content, and the effect of test condition, concrete strength and corrosion time on concrete beams surface corrosion is analyzed. The result show that corrosion time is positively related to corrosion time; the beginning peeling time is longer with the increasing of concrete compressive strength; the capacity of concrete anti-stripping is increased with the increasing of concrete compressive strength. The formula of predication concrete beams surface stripping is set up by use of test data, which can be present in predicating concrete service life.
Properties of concrete containing fly ash and temperature control measures used during construction
Authors: Yu Xinkai , Li Jinyang
Published: September 2019

In recent years, fly ash cement has been applied in engineering with the continuous application of concrete admixtures. Although we have been using fly ash concrete and have done a lot of experimental research, but the understanding of its thermophysical properties was not complete, and further research was needed. This paper presented results of a study into important fundamental thermal and physical properties of both fly ash mortar and fly ash concrete. Different replacement percentage of OPC by FA ranging from 0 to 60% by mass were devised. Increasing fly ash content was found to delay the initial setting time and final setting times, decrease both compressive and flexural strengths and reduce hydration heat. It also can effectively reduce the hydration heat evolution of cement-fly ash binder. The adiabatic temperature rise of cement fly ash material in engineering can be estimated by reduction coefficient k. In fly ash concrete tests, thermal properties, including thermal diffusivity, conductivity, specific heat, ultimate tensile strain and static elasticity modulus were also measured and reported. There also appeared the relationship between compressive strength and flexural strength showed similar linear change with the replacement rate of fly ash rising from 30% to 60%. Most importantly, pipe cooling tests of fly ash concrete were carried out and from the perspective of temperature control of mass concrete, dynamic pipe cooling measures were investigated.
Properties and Engineering Influence of Corewall Filter I with Different Fine Particle Contents
Authors: Huifeng Zheng , Guanye Wu , Yi Chen , Lai Sun , Hua Fu
Published: September 2019

The protection provided by filter I for the corewall constitutes an important safety guarantee for the impervious bodies of corewall dams. In particular, the fine particle content (the content of particles < 0.075 mm in size) of filter I provides a filter protection effect for the corewall. Furthermore, this also determines its own drainage characteristics as an important gradation requirement for filter design. In practical engineering, due to the nature of the aggregate source, the crushing and screening process, and rolling construction, the fine particle content may exceed relevant standards. Relying on the field measured gradation envelope of the filter of a gravelly earth core rockfill dam project, this study prepared two classes of filter I (i.e., filter I of class I with a fine particle content of 8%, and filter I of class II with a fine particle content of 12%). Permeability property test, large-scale compression test, large-scale static triaxial test, and large-scale dynamic triaxial test were conducted. Furthermore, dynamic finite-element calculation of the dam under seismic action was performed, and the anti-seismic liquefaction property of the filter was analyzed. According to the permeability property test, the permeability coefficients of the two classes of filter I were both 1∼5×10−3 cm/s. Lower content of particles < 0.075 mm in size increased the permeability coefficient. According to the mechanical test, the stress-strain test curves of both classes of filter I presented nonlinearity, compressive hardening, elastoplasticity, and other general laws. The strength index and deformation resistance both increased with increasing relative density. Under the same relative density, both strength index and deformation resistance declined with increasing fine particle content. According to the dynamic finite-element anti-seismic liquefaction analysis on filter I of class II (with a content of particles < 0.075 mm in size of 12%) under seismic action, the liquefaction degree had a maximum value of 0.58 (less than 0.8), and the anti-liquefaction safety coefficient had a minimum value of 1.72, which would not trigger liquefaction of filter I. This experimental study and computational analysis offers references for the exploration of the gradation design of filter I of earth core rockfill dams and investigates the related engineering influence.
Effect of cement/lime additive on clogging of vacuum-drain consolidation
Authors: Fu Hongtao , Chai Jinchun
Published: September 2019

All Addressing dredged slurry with high water content has become a critical issue for sea channel dredging and maintenance. Vacuum consolidation is an effective method for improving dredged slurry. Conventionally, the effect of a cement/lime additive on the clogging of vacuum-drain consolidation has been elusive and unclear. To study the effect of vacuum consolidation for soft clayey soils with high initial water content, a set of oedometer tests and vacuum consolidation tests were conducted by adding small amounts of cement/lime. The results indicated that the structural yield stresses of soils with cement and lime were 94.29% and 48.57% higher, respectively, than those of untreated soils. The final surface settlement of lime additive at the end of the tests was 59.68 mm less than that of soil without any additives, and that of the cement additive was close to that of soil without any additives. However, the dissipation of pore water pressure with cement/lime was more than that with untreated soil. The water content was higher when using cement/lime additive, but the vane shear strengths were greater than that of untreated soil at the end of the tests. In addition, the values of k
e2/k
e1 (k
e2 is a permeability at approximately 0.2 m away from the drain, and k
e1 is a permeability close to the drain) above and below the drain were less than those for untreated soil. This clearly indicated that the presence of lime/cement was effective in alleviating the problem of clogging around the drain. This study could provide a good technical guideline for vacuum-drain consolidation projects combined with the use of cement/lime.
Experimental Study on Mechanical Properties of Recycled Concrete with Different Length of Waste Hybrid Fibers
Authors: An Hao , Tian Sisi , Hu Zhengfu , Pei Changchun
Published: September 2019

The mechanical properties of concrete are reduced due to the defects of recycled aggregate itself. In this paper, the fluidity, compressive strength, splitting tensile strength, flexural strength and modulus of elasticity of recycled concrete with hybrid waste fibers were tested by changing the length combination of waste polypropylene fibers and basalt fibers. The test results show that the hybrid fibers can reduce the fluidity, compressive strength and elastic modulus of recycled concrete, and 19 mm waste polypropylene fibers and basalt fibers can significantly improve the splitting tensile strength, flexural strength, brittleness and crack resistance of recycled concrete.
Numerical Study on Temperature Field of Recycled Aggregate Concrete-Filled Steel Tubular Columns Under Fire
Authors: Chen Zheng , Liu Wenchao , Zhang Kesheng , Wang Ruwei , Ren Lele
Published: September 2019

In order to study the characteristics of the temperature field and variation law of steel pipe recycled aggregate concrete column in a fire hazard, this paper takes the thickness of steel pipe and the type of concrete material as the main parameters to carry out fire resistance test of six concrete steel columns simulated by ABAQUS and conducts finite element analysis of the temperature field inside the test piece. The result shows that both the steel pipe recycled concrete column and the ordinary steel tube concrete column have a temperature platform during heating, and their temperature rise is feature hysteresis; the thickness of the steel pipe has little effect on the internal temperature rise while the concrete material is the main factor affecting the heating rate, so steel pipe recycled aggregate concrete column is better fire-resistant. The constitutive model based on the modified parameters in European EC4 specification is used for finite element analysis, and the FEM simulation result is well fitted with the experimental data.
Dynamic parameter identification of a super tall building based on field measurement
Authors: Xiong Chunbao , Niu Yanbo
Published: September 2019

This work aims to identify the dynamic parameters (i.e. natural frequencies and damping ratios) of a super tall building under construction (i.e., Tianjin 117 Tower). Real time kinematic - global navigation satellite system (RTK-GNSS) receivers are applied to monitor the vibration of the structure. Considering the errors of receivers, a joint denoising method is proposed to weaken the influence of noise. Meanwhile, random decrement method (RDM) and fast Fourier transform (FFT) are adopted to derive the dynamic parameters of the structure. Moreover, the identified results from field measurement are compared with predicted values obtained from finite element model (FEM) of the structure. The outcomes of this study are that: (1) the proposed joint denoising method can be employed to weaken the RTK-GNSS observation errors; (2) the first natural frequency of the structure is derived successfully based on FFT analysis, and it agrees well with the finite element results; (3) the damping ratio of the structure is obtained by using RDM.
Effect of the interaction between rebar and concrete cover on the concrete compressive strength
Authors: Li Zhenbao , Yu Chunyi , Ma Hua , Xie Yongping , Zhenyun Tang
Published: September 2019

In order to analyze the effect of rebar size on the compressive strength of concrete cover, the axial behavior of a prism with a central rebar was experimentally and theoretically investigated. The test results indicated that the concrete compressive strength with rebar was relatively smaller than the axial compressive strength of prism that was similar with the concrete strength of cylinder. Further, the degree of reduction in the concrete compressive strength increased as the diameter-thickness ratio increased. Moreover, based on the test results and walled cylinder theory, the influence of rebar on the concrete compressive strength can be better understood. Lastly, in the structural design, the small rebar size and big concrete cover thickness should be chosen so that the effect of splitting action on concrete cover was weaken.
GFRP Reinforced Concrete Adhesion in Low Temperature Environment
Authors: Derui Huang , Wei Jiang , Kuizhou Liu , Yujie Shen , Zhonghua Huang , Yang LI
Published: September 2019

In order to study the bond properties of GFRP reinforced concrete at low temperature, a test device for mechanical loading and strain testing at low temperature was designed and developed. The effects of temperature, diameter of GFRP bar and bond length of GFRP bar and concrete on the bond properties of FRP bar concrete were studied. The study shows that the temperature is reduced from -10 °C to -30 °C, and the bond performance of GFRP reinforced concrete is increased by 15.5 % to 40 %, and the bond performance is enhanced by the load. Adhesive properties also become smaller as the bond length and GFRP diameter increase.
Experimental study on impermeability of concrete lining joint
Authors: He Xiaonan , Guo Xiaohong , Li Sen , Xu Guodong
Published: September 2019

In tunnel and shaft construction, the impermeability of concrete lining joint is involved with the safety of the lining structure. The chloride ion diffusion test is used to test the impermeability of concrete sample. The orthogonal test is designed with three factors, including water-cement ratio, waterproof interface form and prestress load. Each factor establishes three levels. The test results show that the interface form has the greatest influence on impermeability, followed by the prestress load, which can be used to optimize the design of concrete lining joints.
Structural durability and concept system of structural reliability
Authors: Jitao Yao , Liuzhuo Chen , Jun Gao , Ren Xin
Published: September 2019

Research on durability is vital for reliability analysis and control. The main aim is to analyze the deterioration of concrete structures resulting from material degradation. While there is still a large difference in understanding the concept of the structural durability, and a misunderstanding of the relationship among safety, serviceability, and durability, which influence the process of establishing the structural reliability concept system, and the analysis and control of structural durability. Based on former researches and the definition of “condition limit state” in an international standard, the concept of structural durability and the relationship among safety, serviceability, and durability of a structure are elucidated clearly. Furthermore, the basic solution to durability analysis and control is put forward, and the concept system of structural reliability is built. The research will lay the foundation of defining the structural durability uniformly, measuring the structural durability reasonably, and analyzing and controlling structural reliability and structural durability effectively.
Effects of soil grading and sand content on soil-cement properties
Authors: Yao Xianhua , Guan Junfeng , Bai Weifeng
Published: September 2019

The effect of soil-cement characteristics, unconfined compressive strength (UCS), dry density, and water absorption on the soil grading and sand content of six groups (natural soil, ≤ 2 mm, ≤ 1 mm, ≤ 0.5 mm, ≤ 0.25 mm, and ≤ 0.075 mm) of soil-cement block was studied. The results showed that the characteristics of soil-cement mixed with sand were influenced by soil grading. Better characteristics of soil-cement soil were obtained when the soil particle sizes of soil-cement were less than 0.075 mm of mixed sand. Every soil particle size has optimal sand content. Results showed that the optimal sand content of natural soil is 40%, whereas those of other soil particle sizes are all 55%. The results also showed that the UCS of 28-day ages is 1.79 times that of natural soil for soil-cement mixed with sand of ≤ 0.075 mm particle group, whose water absorption is 50% that of natural soil as the optimal sand content. Finally, the study of clay content showed that there exists an optimal clay content for various size groups, namely, 9.12%, 7.06%, 8.08%, 9.05%, 11.36%, and 13.60% for natural soil, ≤ 2 mm, ≤ 1 mm, ≤ 0.5 mm, ≤ 0.25 mm, and ≤ 0.075 mm, respectively.
The Low Viscosity Loess Liquefaction and its Microstructure Analysis
Authors: Dengjin  , Lina  , Lipin
Published: September 2019

Low viscosity powder loess is widely distributed in loess plateau areas of northwest China. It has a high liquefaction potential. the mechanism of low viscosity loess water action is studied using CT scanning. CT scanning results showed that initially, water in loess will tend to rise as a whole. Then, cement salts around the loess grains melt and form large holes. Finally, deformation collapse and damage can occur. In this study, low viscosity loess is compared with sand loess and clayey loess obtained from Lanzhou, Guyuan, and Tongguan. Based on the results of dynamic triaxial torsion tests, the low viscous powder loess dynamic loading time was shorter and more easily liquefied than sandy loess and clayey loess. Electron microscope scanning of loess microstructures showed the chemical element ratios around the loess particles produced cemented material (such as Ca/Fe). The chemical elements around loess particles and the pore diameter/grain ratio were selected to evaluate liquefaction resistance in loess. In addition, loess particle size distribution and the pore/grain ratio also influenced the liquid level. It is an effective innovative method to judge the liquefaction strength of low viscosity silt based on microcosmic parameters.
Experimental Research on Mechanical Properties of Frozen Sands under Isotropic Compression Conditions
Authors: Luo Fei , Lei Jian , Lv Siqing , Xi Yuxuan , Song Zhijie , Zhang Junkai
Published: September 2019

The K-G model has better practicability and superiority than the E-μ model. Conventional triaxial tests of frozen sand samples were carried out at -10 C under confining pressures of 0.5 MPa, 1.0 MPa, 2.0 MPa, 4.0 MPa and 6.0 MPa. During the consolidation process, the samples behave an isobaric state. While the confining pressure σ3 is unchanged, axial pressure σ1 is gradually increased during the shearing process. The test results show that the volumetric strain increases nonlinearly with the increase of the volumetric stress in the isobaric state, showing a power function trend. An improved K-G model is proposed to describe strain softening of frozen sand during shear. The verification results show that the model has good applicability.
Research Progress and Prospects of Soil Pollution Assessment and Prediction Models
Authors: Li Xiuxia , Zhu Wei , Qin Yufang , Yin Fei
Published: September 2019

Soil pollution has become a worldwide environmental problem. The assessment and prediction of soil pollution status is also the focus of scholars at home and abroad. In general, the soil pollution assessment and prediction has experienced the field investigation phase, the statistical analysis phase and the process simulation phase, each of which reflects different levels of the discipline. With the enhancement of today’s big data processing technology and management capabilities, as well as the increasing popularity of aerial remote sensing(RS) and unmanned aerial vehicle (UAV) low-altitude RS applications in the environmental field, it is necessary to integrate these new technologies in time to develop highly efficient models to provide strong technical supports for soil pollution control and restoration decision-making.
Study on Concrete Stress during Construction for Large Pumping Station Flow Channel Structure under Thick-layer Pouring Condition
Authors: Zheng Xuerui , Shen Zhenzhong , Qiang Sheng , Xu Pu
Published: September 2019

Large pumping stations have the characteristics of complex structure, large amount of concrete pouring block, easy cracking of concrete and long construction period, etc. For the stress safety of the flow channel structure during construction period, temperature control simulation for a large pumping station during construction period is carried out. By comparing and analyzing the variation law of temperature field and stress field of the two types of pouring layers which are one 6m layer and two 3m layers, the influence of thick-layer pouring on concrete stress is studied. The simulation results show that thick-layer pouring may cause the increasement of tensile stress peak in concrete structure, but this adverse effect can be eliminated by appropriate temperature control measures. The effect of the same temperature control measures on the reduction of tensile stress of thick-layer concrete structure is more obvious. Thick-layer pouring can shorten the construction cycle of pumping station under the premise of ensuring safety which has a wide application prospect in the field of concrete construction.
Seeping Performance of Reinforced Concrete Slab Dam
Authors: Tao Liu , Qan Yan , Youbo Wang , Zhan Xiong , Yajun Wang , Gan Xiao-qing , Dong Zhi-hong
Published: September 2019

Taking the panel dam as the research object, the finite element simulation analysis and the design working condition scheme comparison method are used to study the impermeability of the panel dam. The results show that the anti-seepage system is the key guarantee for the safety of the dam body, and it plays an important role in the anti-seepage safety of the dam system under the limit state. At the same time, the complete and effective upstream and downstream anti-seepage drainage system has obvious effects on the overall safe operation of complex hydraulic large-scale systems such as reinforced concrete face rockfill dams.
Chemical-Physical Mechanism of Marine Sediments
Authors: Wang Mingyuan , Shan Zhigang , Liu Tao , Xiong Zhan , Yan Qian , Wang Yajun
Published: September 2019

The target material of this study is the marine depositions from Eastern Seas of Zhejiang. The comprehensive experiments were implemented to discover the chemical-physical mechanism and the micro-fabric of the target material. The results of this study will help many maritime explorations such as geophysical prospection, coastal reinforcement, resource exploitation as well as marine structure establishment.
Effects of nitrogen application on growth and yield of maize
Authors: Han Xiaonan , Han Nana , Zhou Qingyun , Kang Jie , Bai Xinyan
Published: September 2019

The effects of different nitrogen application levels on growth, dry matter accumulation, SPAD value, leaf area index and yield of maize were studied to provide theoretical basis for rational and efficient nitrogen application management of crops. In the field experiment, 225, 337.5, 450, and 675 kg ·hm−2 nitrogen application levels were set, respectively expressed by N1, N2, N3, and N4. N0without nitrogen fertilizer was used for the control experiment. During the growing period, plant height, leaf area index and SPAD were observed, and dry matter accumulation, yield and yield components were counted. The growth index, dry matter accumulation, yield and yield components of maize were influenced by different fertilization levels. When the nitrogen application amount is greater than 225 kg · hm−2, it could significantly promote the growth and development of corn and increase the yield. Through comparative analysis, it was concluded that when the nitrogen application amount was 280kg·hm−2, it was the optimal nitrogen application amount for the efficient production of corn in the experimental area.
Construction Simulation and Real-time Monitoring Research of Concrete Dam Based on BIM
Authors: Ji Shunwen , Hu Tianhan
Published: September 2019

Concrete is a complex multiphase composite. Along with the hydration reaction, the thermal and mechanical properties of concrete continue to increase, resulting in deformations such as temperature, autogenous volume and shrinkage, and stress and creep after being restrained by themselves and externally, further cracks are formed. Through finite element simulation, the key parts of temperature control and crack prevention of concrete dam can be predicted, and targeted crack prevention measures can be proposed. Therefore based on BIM technology and combined with simulation results, this paper conducts real-time monitoring of concrete temperature and stress during construction. Through comparison and inversion analysis, the whole process dynamic management of temperature and stress during dam construction period is implemented, and temperature control measures are optimized in real time to realize the whole process control of temperature control and crack prevention of concrete dam.
Study on Sediment Management Strategy of Sandy River Reservoir
Authors: Jinqiong Zhao , Guanghui Rao , Junjie Hua
Published: September 2019

The establishment and operation of one hydropower complex will change the movement law of water flow and sediment of the river way, and sediment deposition is difficult to avoid. Due to the characteristics of “high utilized water head, small reservoir storage, high sediment content and particle hardness” of proposed Upper Arun Hydroelectric Project, this paper applies one-dimensional hydrodynamic & sediment model to studying the movement law of flow and sediment of 3 different sediment management strategy, then finding the rational one which can not only maintain a sustainable live storage of the reservoir by sediment flushing, but also reduce sediment abrasion to turbines. The results show that, when the proposed fully open of all low-level outlets for sediment flushing being implemented during high flow periods, the difference of sedimentation is relatively minor, which all 3 options can effectively maintain the live storage of the reservoir thereby minimizing deposition of sediment at the places that will affect project operation. Therefore, the selection of sediment management strategy should depends on the comprehensive technical and economic comparison. Due to the advantages of relatively short outage periods, conventional technology of construction and the largest Net Present Value, the appropriate sediment desilting operation mode is applying a sediment bypass tunnel with its intake located in the middle of reservoir, and meanwhile utilizing the reservoir’s sedimentation effect, to reduce sediment content transported through the turbines.
Experimental Study on the Triaxial Stress-strain Curve of Undisturbed Loess in Xining by Freeze-thaw Cycles
Authors: Li Shuanghao , Li Yuanxun , Gao Xinya , Shi Dongmei
Published: September 2019

The undisturbed loess in the high-altitude and high-altitude Xining area was studied. The triaxial shear tests of different freeze-thaw cycles and different confining pressures were carried out to investigate the stress-strain changes of undisturbed loess before and after freezing and thawing. The test results show that: (1) different stresses are applied to the samples to show different stress-strain curves. Low confining pressure is strain softening; high confining pressure is strain hard. (2) When the number of freeze-thaw cycles is 0, 1 time, the initial stress phase at different confining pressures is interlaced; when the freeze-thaw cycle is 3 times, in the later stage of strain, the growth rate is 30%-50%. The freeze-thaw effect has a great influence on the internal strength of the soil structure.
Underreamed Anchor with Geotextile Bag and Its Hyperbolic Load versus Displacement Model for Capacity Prediction
Authors: Guo Gang , Tang Aiping , Zhong Guang , Liu Zhong , Hu Xiaochen
Published: September 2019

Underreamed ground anchor technologies have been developed to increase the capacity of ground anchors referring to reamed piles worldwide. To solve the problem of low anchor cement strength caused by muck and slag in the borehole for a traditional underreamed anchor, this paper introduces an underreamed ground anchor with a geotextile bag. Its structure and installation process are both discussed in detail. Based on the test data from 24 underreamed anchors with geotextile bags at 6 construction sites all over China, a hyperbolic model of the relationship between the load and displacement is presented to predict the capacity of a cylindrical underreamed anchor. Compared with the measured values, the predicted capacities of pointed displacements out of the tested range were sufficiently accurate for engineering practice.
Test Research on Mechanical Property of Cemented Soil Strengthened with Basalt Fiber
Authors: Chen Feng
Published: September 2019

To enhance the mechanical property of cemented soil, this paper discusses the way of improving the mechanical performance by incorporating basalt fiber into cemented soil. Unconfined compressive strength test is conducted on cemented soil with basalt fiber of different proportions, and the results show that the incorporation of basalt fiber can significantly improve the compressive strength of the cemented soil samples at different ages, but its strengthening effects weaken steadily with the increase of fiber amount. The incorporation of basalt fiber can enhance the plasticity of cemented soil, and the sample at its peak stress can still bear some loading, with some residual strength existing, propitious for the enhancement of engineering safety and stability. Additionally, the relations between the compressive strength and ages of cemented soil with basalt fiber of different proportions are established based on the experiment results, which can provide some references for practical projects.