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Table of Content

    28 November 2018, Volume 52 Issue 11 Previous Issue    Next Issue
    Turbulence Characteristics of Turbulent Wind Field Based on Multifractal Theory
    WANG Guang,SHEN Xin,ZHU Xiaocheng,DU Zhaohui
    2018, 52 (11):  1417-1421.  doi: 10.16183/j.cnki.jsjtu.2018.11.001
    Abstract ( 941 )   Save
    In order to quantitatively analyze the inherent volatility of wind speed data, multifractal method is used to study the turbulence characteristics of turbulent wind field. The commonly used model of turbulent wind is introduced, based on the model wind speed data of different surface roughness are obtained. The fractal dimensions of different wind speed data are calculated with structure function dimension method, and the influence of surface roughness on the fractal dimension of wind speed data is considered. The wind speed data are analyzed with multifractal detrended fluctuation analysis method to explore the intrinsic structure of turbulent wind. And the results show that the greater the surface roughness is, the smaller the fractal dimension, the smaller the Δα (Δα is the ratio of the largest to the smallest constituent elements), and the bigger the |Δg| (Δg is the ratio of the probability of occurrence of the largest and smallest constituent elements).
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    Effects of Rake Angle on Linear Rock Cutting with Chisel Picks
    OUYANG Yiping,YANG Qi,MA Jian,QIU Yiping
    2018, 52 (11):  1422-1428.  doi: 10.16183/j.cnki.jsjtu.2018.11.002
    Abstract ( 49 )   Save
    In order to investigate the effects of rake angle on rock cutting, a linear rock cutting device was invented and used to conduct rock cutting experiments with chisel picks on sandstone with rake angle ranging from -40° to 50°. The interaction forces between picks and rocks were real-time recorded. The grooves created in the experiments were captured. The pieces of debris were collected and the size distribution was obtained. The fractal features of the debris pieces were analyzed. And the debris pieces’ size distribution was quantitatively described by their fractal dimension. The results show that with the increasing of rake angle from -40° to 50°, the width of the groove increases, especially in the initial part of the groove. The fractal dimension of the debris and the cutting force on the picks decrease gradually with the increasing of the rake angle. They can be expressed by the exponential function of the rake angle. However, the ratio of mean cutting force to mean normal force remains between 0.56 and 1.84, and seems not be affected by the rake angle.
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    Long-Term Deformation Characteristics of Shanghai Soil Layer and Its Influence on Infrastructure
    WU Wei, LI Mingguang, SHI Yujin, WANG Jianhua
    2018, 52 (11):  1429-1436.  doi: 10.16183/j.cnki.jsjtu.2018.11.003
    Abstract ( 466 )   HTML ( 1565 )   PDF (3782KB) ( 362 )   Save

    Based on the shallow and deep soil deformation data, the deformation data of the aquifer and the water level, the deformation data of the infrastructure (mainly the subway tunnel, the elevated and the ground roads), we studied the deformation characteristics of the deep soil layer and shallow soil layer in Shanghai, and discussed the deformation characteristics of subway tunnels, elevated and ground roads under the combined deformation of shallow and deep soil layers, and reached the following conclusions. First, the shallow soil layers are in continuous compression, and the total amount of compression is small. The deep soil greatly compressed before 2009, and has gradually expanded since then. Second, the deformation of the confined aquifer in Shanghai is closely related to the water level of the soil layer. When the water levels of the first, second, third and fifth aquifer rise, the soil layer rapidly expands. The expansion of the fourth confined aquifer is lagging behind the rise of the soil water level. Last, deep soil layers have similar deformation trend with the infrastructure, and shallow soil layers with different thickness affect the deformation of the infrastructure. The infrastructure near the deep soil layer has obvious uplift deformation, accompanied by the expansion of deep soil layer. Under the same conditions, the infrastructure with thick shallow soil layer shows greater settlement than that with thin shallow soil.

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    Mechanism Analysis of Influence of Deep Excavation on Deformation of Nearby Cut-and-cover Tunnel
    XIAO Xiao, LI Mingguang, XIA Xiaohe, WANG Jianhua
    2018, 52 (11):  1437-1443.  doi: 10.16183/j.cnki.jsjtu.2018.11.004
    Abstract ( 483 )   HTML ( 194 )   PDF (1749KB) ( 325 )   Save

    A practical numerical example is used to simulate the excavation process of a deep foundation pit in Shanghai, and the rationality of the model is verified by comparing with the measured data. The cross wall between tunnel and diaphragm wall is studied and the influence of cross wall is discussed. By analyzing the vertical displacement of adjacent walls and the displacement of soil on both sides of diaphragm walls, the interaction principle between diaphragm wall and tunnel or diaphragm wall and soil is obtained. The force distribution of the wall in the excavation process is used to reveal the influence principle of adjacent deep excavation on underground structure (cut-and-cover tunnel). The results show that the uplift of the tunnel is mainly caused by the uplift of the nearby diaphragm wall. The influence of the diaphragm wall on the cut-and-cover tunnel is obviously greater than that of the surrounding soil. Under the influence of deep excavation, the reason for the diaphragm wall uplifting is that the friction force in the foundation pit is larger than that of outside the pit.

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    Field Test of Mechanical Properties of Large Diameter Steel Jacking Pipe Under Construction and Temperature Load in Soft Soil
    MA Helong, LIAO Chencong, WANG Jianhua, LI Yaoliang
    2018, 52 (11):  1444-1451.  doi: 10.16183/j.cnki.jsjtu.2018.11.005
    Abstract ( 457 )   HTML ( 198 )   PDF (4947KB) ( 273 )   Save

    Circumferential and longitudinal strain of steel jacking pipe which is buried in deep soft soil and jacked with long distance was monitored on the spot to study internal force of pipe under construction and temperature load. The results show that internal force of a fixed section changes little due to jacking distance. For different sections, the one that is closer to the jacking machine head is affected less by jacking force. Compressive stress predominates in longitudinal direction, and is mainly affected by jacking force. However, circumferential stress is mainly due to buried depth, and maybe tensile with deep buried on top of pipe. Circumferential stress and longitudinal stress are coupling especially with large buried depth. Eccentricity of jacking force has a great effect on internal force of pipe. When jacking force is applied, longitudinal stress changes by a large margin, and returns to steady after jacking force removed. The stress in pipe can reach 25 MPa caused by 6 ℃ temperature difference, which hardly influences the using of the pipe. There is little distinction between longitudinal stress and circumferential stress. However, extreme range of temperature should be valued, and may cause destroying.

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    Indoor Thermal Environment Measurement of Enclosed Gymnasium with Membrane Structure in Winter
    YIN Yue,HU Jianhui,CHEN Wujun,LI Yipo
    2018, 52 (11):  1452-1458.  doi: 10.16183/j.cnki.jsjtu.2018.11.006
    Abstract ( 45 )   Save
    Indoor temperature measurement of an enclosed gymnasium under membrane structure with natural ventilation was carried out during winter period. Air temperatures were measured from six positions with different heights and directions. Parameters relating to thermal environment were obtained, including indoor irradiation, velocity, globe temperature and relative humidity. This paper aimed to study indoor temperature distribution of the gymnasium and evaluate its thermal comfort by revised PMV-PPD index (aPMV-aPPD index). The results show that indoor irradiance is the main factor which effects the variation of indoor temperature. Mean air temperature inside was 3℃ higher than that outside. Air temperatures near the interior surface of the membrane roof kept higher in vertical direction and both amplitude and phase of the temperature decayed at positions in lower altitude. The aPMV value of the gymnasium inside ranged from -1.2 to -0.5 while aPPD varied from 15% to 40%. Without thermal insulation design in membrane structures, indoor environment in enclosed gymnasium hardly satisfies comfortable requirement under natural ventilation condition.
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    Spatial Active Earth Pressure Against Translating Retaining Walls in Square Shaft Excavations
    YING Hongwei,LIANG Wenpeng
    2018, 52 (11):  1459-1466.  doi: 10.16183/j.cnki.jsjtu.2018.11.007
    Abstract ( 37 )   Save
    In order to study the distribution of spatial active earth pressure against retaining walls in square shaft excavations, a 3-dimensional finite element analysis model of orthogonal rigid retaining walls is established, and the distribution of spatial active earth pressure and variation of the spatial slip block against translating retaining walls with different aspect ratios are studied. A theoretical model for determining spatial active earth pressure against translating rigid retaining walls with different aspect ratios is proposed. The definition of deep shaft excavations is given. The theoretical formulae for the resultant earth pressure and its acting point and the active earth pressure in the middle section of the wall are presented. Comparing the theoretical and numerical results, it is found that the two are in good agreement. The studies indicate that the spatial slip block consists of Coulomb’s active soil wedge in the middle of the wall and object with curved surfaces in the corner when the aspect ratio of the retaining walls is larger than the critical aspect ratio. When the aspect ratio of the retaining walls is less than the critical aspect ratio, it can be defined as a deep shaft excavations whose sliding block does not have straight section. As the decrease of aspect ratio, the active earth pressure coefficient decreases gradually from the Coulomb’s solution and the sliding angle increases.
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    A Comparative Study on the Static Drill Rooted Nodular Piles Under Tension and Compression
    GONG Xiaonan,XIE Cai,ZHOU Jiajin,SHAO Jiahan,SHU Jiaming
    2018, 52 (11):  1467-1476.  doi: 10.16183/j.cnki.jsjtu.2018.11.008
    Abstract ( 37 )   Save
    The pre-bored grouting planted nodular (PGPN) pile is a new type of composite pile foundation. A large number of field test results have shown that the ultimate skin friction of piles under tension and compression has big differences. The total lateral friction reduction factor is defined as the ratio of shaft resistance between uplift pile and compressive pile. To investigate the differences of skin friction distribution of the PGPN piles under tension and compression in soft soils, a group of field tests were carried to obtain the load-displacement curves of piles under tension and compression, and then Abaqus was used to simulate test piles. The comparison between results of field tests and Abaqus simulation was used to validate finite element model. The results showed that the axial forces of piles under tension and compression have similar transfer characteristics; the uplift coefficient of the PGPN piles in soft soils is 0.5. The increase of diameter of enlarged pile tip has little effect on ultimate skin friction of piles under tension and compression. The total lateral friction reduction factor of the PGPN piles is a constant with the increase of the diameter of enlarged pile base.
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    A Method of Reckoning Nodal Positions of Existing Grid Shell Structures Based on Surface Interpolation
    LIU Jun,LUO Yongfeng,YANG Xu
    2018, 52 (11):  1475-1482.  doi: 10.16183/j.cnki.jsjtu.2018.11.009
    Abstract ( 40 )   Save
    A new method was proposed to reckon the nodal positions of an existing grid shell structure using surface interpolation, based on the structural characteristics of the high in-plane stiffness and overall capacity of load bearing. In the proposed method, the degree of structural deformation is estimated firstly by statistical analysis of nodal deviations. Then horizontal nodal coordinates are calculated by regression equations from statistic regression analysis theory. Lastly, vertical nodal coordinates can be determined by the structural shape and interpolation from the measured nodal positions according to surface interpolation theory. By applying the proposed method to the practical grid shell structures, it was concluded that the method can give realistic results and is effective for the assessment of existing structures.
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    Influence of Corrosion Forms on the Degradation Process and Sulfate Diffusion Laws of Cast-in-Situ Piles
    ZHAO Gaowen,LI Jingpei,LI Lin,CUI Jifei
    2018, 52 (11):  1483-1491.  doi: 10.16183/j.cnki.jsjtu.2018.11.010
    Abstract ( 40 )   Save
    Sulfate corrosion process of the cast-in-situ piles in the saline area was simulated by laboratory experiments. Comparison study of degradation process and sulfate diffusion laws of cast-in-situ pile concrete was conducted to reveal the degradation mechanism. Cast-in-situ concrete specimens were manufactured and immersed in sulfate solutions to reproduce the completely and semi-immersed service conditions of cast-in-situ concrete piles in practical engineering. The size changes were recorded after 1, 3, 6 and 9 months. The compressive strength test was conducted and the sulfate concentration of different depths in concrete were measured to reveal the differences of degradation process in different service conditions. The effect of service condition on diffusion properties of sulfate in pile concrete were analyzed based on the experiments. Results show that degradation process of concrete and sulfate diffusion in concrete are quite different in different service conditions. The deterioration of concrete semi-immersed in sulfate solution is faster than those completely immersed below the liquid surface. Expansion and shedding of concrete are detected since sulfate chemical and crystallization conducted on the surface of semi-immersed specimens. The sulfate diffusion ratio in concrete above the liquid surface is more rapid than that of specimens completely immersed in sulfates solution. Results indicate that pile concrete above the groundwater level suffers greater damage and encounters more serious degradation in a relatively short time. The deterioration of pile concrete below groundwater level is relatively slow since the serving environment is stable and only chemical attack is encountered. The anti-sulfate attack of cast-in-situ pile concrete near the groundwater level should be considered in the design of pile foundation in sulfate saline area.
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    Experiments of Soil Conditioning for Shield Tunneling in Watery Quartz Sand-Gravel Ground
    CHENG Chihao,LIAO Shaoming,CHEN Lisheng,FAN Mingxing,HUO Xiaobo
    2018, 52 (11):  1492-1500.  doi: 10.16183/j.cnki.jsjtu.2018.11.011
    Abstract ( 35 )   Save
    Through a shield project in watery quartz sand-gravel ground, a series of soil conditioning tests are conducted. Then optimal parameters are obtained under natural water content, namely injection ratio of foam 10% and slurry 23%~25%. Based on formulas of laboratory tests and construction feedback, pressure balancing of soil chamber and screw conveyer should be closely focused. Cutter torque should be controlled in the normal range, while at the same time slumps and consistency of mucks should be about 20cm and 8cm, respectively. The relevant results can be used to provide references for soil conditioning by use of EPB machine in similar ground conditions.
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    Reasonable Method of Tunnel Anchorage Uplift Stability Coefficient in Mountain Areas
    WANG Dongying,TANG Hua,DENG Qin,YIN Xiaotao,QIN Yuqiao,TAN Yinhua
    2018, 52 (11):  1501-1507.  doi: 10.16183/j.cnki.jsjtu.2018.11.012
    Abstract ( 42 )   Save
    In order to study the reasonable assessment method of the safety coefficient of tunnel-type anchorage, three different methods—stress integration method, displacement load curve method and plastic area-load curve method are used to solve the uplift stability coefficient of tunnel-type anchorage. And the specification value is also given to make a comparison with the values obtained from the three methods. Results show that the stability coefficient given by specification method is comparatively small because this method neglects the clamping effect of rock to anchor. The value of safety coefficient calculated by this method is only 2.60. And stress integration method takes the stress field corresponding to the design load as the calculation stress, in which case the clamping effect is out of action. Therefore, the coefficients calculated by this method are close to the value of specification method. The safety factor calculated by this method is 2.64 when the failure mode of tunnel-type anchorage is interface failure. And the value is 2.88 while the failure mode is rock failure. In addition, the safety coefficient obtained from both plastic area-load curve and displacement load curve methods are 6.50, the biggest value of all methods. Because the rock and anchor contact each other closely and the clamping effect works effectively under the maximum permitted load. Last but not least, the uplift safety coefficient of tunnel-type anchorage with the clamping effect into consideration can be calculated when the bearing force of interface can be calculated by the ultimate lateral resistance.
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    Analysis and Prediction of Factors Affecting Horizontal Displacement of Foundation Pit Based on RS-MIV-ELM Model
    ZHONG Guoqiang,WANG Hao,ZHANG Guohua,QIN Weimin WANG Chengtang,XIONG Junfeng
    2018, 52 (11):  1508-1515.  doi: 10.16183/j.cnki.jsjtu.2018.11.013
    Abstract ( 43 )   Save
    In order to predict the maximum horizontal displacement and depth of the inclinometer in the foundation pit, an RS-MIV-ELM model based on rough set attribute reduction, mean impact value and extreme learning machine was proposed. The model was based on systematic analysis and quantification of deformation factors, the attribute reduction algorithm of rough set (RS) and the mean impact value based on the extreme learning machine algorithm (ELM-MIV) were used to remove the redundant factors and small correlation factors respectively. Then, the extreme learning machine (ELM) model was trained by the simplified influence factor set, and the model was used to predict the displacement of other measuring points. Experimental results show that the training speed, prediction accuracy and generalization ability of the proposed model are better than those of the all factors ELM model and the BP neural network model based on the simplest set. The root mean square error or average relative error of RS-MIV-ELM model is about 1/2~2/3 of the two contrast models.
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    Interpolation Prediction and Extrapolation Prediction of Non-Gaussian Spatial Wind Pressure Using LSSVM with Wavelet Kernel Function
    LI Chunxiang,YIN Xiao
    2018, 52 (11):  1516-1523.  doi: 10.16183/j.cnki.jsjtu.2018.11.014
    Abstract ( 38 )   Save
    The performance of support vector machine depends on the selection of kernel functions and kernel parameters. The Mexican Hat wavelet kernel function is constructed based on the wavelet analysis theory which could satisfy the Mercer conditions. Further, the Mexican Hat wavelet kernel function and the B-spline kernel are combined with the LSSVM respectively and accordingly MW-LSSVM and BS-LSSVM are proposed. Subsequently, optimizations for penalty parameters and kernel parameters are conducted using particle swarm optimization (PSO) and thus the PSO-MW-LSSVM and PSO-BS-LSSVM algorithms are proposed for spatial wind pressure prediction. The numerical analysis shows that the proposed method not only significantly outperforms the conventional RBF-LSSVM and BS-LSSVM in forecasting accuracy and generalization ability, but also has great engineering application prospects due to its stability.
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    Numerical Parallel Simulation and Application of Building Fire Based on Load Balance Domain Decomposition Method
    JIANG Lielin,YANG Peizhong,SHI Chao
    2018, 52 (11):  1524-1531.  doi: 10.16183/j.cnki.jsjtu.2018.11.015
    Abstract ( 44 )   Save
    Aiming at the problem of occupying large computation resources in the process of building fire numerical simulation, a new parallel computation method based on load balance is proposed. The method is based on the characteristics of number of grid, communication boundary, fire location and combustible density. This method is applied to the wholesale market large fire parallel numerical simulation, and the results show that this method has better parallel efficiency, and verify the feasibility of the method, compared with the traditional topology partition method.
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    Experimental Study on the Anti-Icing Performance of Plasma Jet II. Comparison of Anti-Icing Performance Using Streamwise and Spanwise DBD-PA
    ZHAO Binbin,DONG Wei,ZHANG Yi
    2018, 52 (11):  1532-1536.  doi: 10.16183/j.cnki.jsjtu.2018.11.016
    Abstract ( 39 )   Save
    The anti-icing performances of streamwise and spanwise plasma jet actuators fixed on NACA0012 are compared in the icing wind tunnel. Streamwise and spanwise actuators are designed and installed on the model surface, and thermocouples are specially embedded beneath the actuator to detect the anti-icing effects. Experiment results indicate that the spanwisely installed actuator cannot generate plasma jets due to the installation position being above the exposed electrode, leading to icing and thus a poor performance of anti-icing, while the streamwisely installed actuator realizes anti-icing by contrast.
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    Construction of Typical Driving Cycle for Passenger Cars in the City of Dalian
    CAO Qian,LI Jun,QU Dawei
    2018, 52 (11):  1537-1542.  doi: 10.16183/j.cnki.jsjtu.2018.11.017
    Abstract ( 39 )   Save
    In order to construct a reasonable typical driving cycle of passenger cars, an arithmetic that based on Markov chain principal was proposed and the driving features were investigated based on driving data in the city of Dalian by adopting cluster analysis. The typical driving cycle of passenger cars was constructed and comparison analysis of driving features between the constructed typical Dalian driving cycle and the existing available driving cycles was applied. Results show that the average absolute deviation of driving characteristic parameters between the constructed driving cycle and driving database population is 4.42%. This value indicates that the development requirement that the deviation must be under 5% is met and the validness and accuracy of the constructed arithmetic is verified. Remarkable region discrepancy of driving characteristics of passenger cars exists in domestic cities. NEDC (New European Driving Cycle) can hardly characterize the domestic driving characteristics correctly. Thus, it is necessary to construct driving cycle which can correctly reflect the domestic actual driving features. The results can provide beneficial references for arithmetic of constructing driving cycle and analysis of driving characteristics.
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