Lagged Surface Collapse Mechanism of Shield Construction in Sandy Pebble Stratum

As for many lagged surface collapse cases that shield crosses the sandy cobble stratum in Chengdu metro No.1 and 2 lines, lagged surface collapse mechanism in sandy pebble stratum was studied. Conditions of engineering geology about sandy cobble stratum were analyzed. Mechanical behavior of sandy pebble was obtained via large-scale tri-axial test. Discrete element method was adopted for numerical computation on lagged surface collapse mechanism. According to the tri-axial numerical test method, the relation between the micro parameters and macro parameters of the sandy pebble stratum layer in Chengdu was calibrated. The face failure of shield tunneling and upward movement of cavity was simulated by numerical calculation. When supporting pressure is small, the particles with the displacement of over 0.1 m have low contact force. The porosity of earth in the region becomes larger and its mechanical behavior becomes worse. Therefore the region can be identified as instability region. Cavity in the ground will be caused after shield tunneling. Soil arching effect is obvious under shield construction. Even though there is cavity in the ground, surface collapse will not bring about immediately. This is important reason for lagged surface collapse phenomena of shield construction in sandy pebble stratum.     

Face Stability Analysis of Shield Tunneling in Sandy Cobble Stratum

When shield crossed the sandy cobble stratum in Chengdu metro line 1, ground subsidence reached as high as dozens of times. The losing stability of excavation face caused excessive ground loss. Conditions of engineering geology and hydrogeology about sandy cobble stratum in Chengdu were analyzed. Mechanical characteristics of sandy cobble were obtained via large-scale triaxial test. According to the low cohesion and heavily discrete characteristics of sandy cobble, numerical computation was conducted by discrete element method. Based on numerical simulation of the large scale triaxial test, the micro parameters of the sandy cobble were calibrated. The influence of support pressure on shield excavation face deformation, surface settlement, max horizontal displacement and stress of soil was analyzed. The results show that: 1) Collapse pattern of excavation face by numerical simulation coincides with result of centrifuge model test in sand. 2) When supporting pressure is small, contact forces of particle in front of excavation face is low. The tendency of particle flow is apparent. Since over-excavation is easily brought out, cavity in the ground is caused after shield tunneling. 3)Soil arching effect in shield construction is obvious. Shield excavation forms cavity in deep ground and obvious earth surface collapse is not observed. This is main reason for lagged settlement phenomena of shield tunneling in Chengdu.     

Solving Method for Soil Spring Stiffness of Shallow Shield Tunneling

Based on complex variable theory in plane elasticity, the equivalent spring stiffness is derived from the analytical solution by means of simplifying shallow shield tunneling to semi-infinite plane with hole, which is applied to response displacement method. The performances of the analytical solution are evaluated and compared with that of the deep shield tunneling through a series of selected various tunnel depths and soil Poisson's ratios. The relation of compression and shear spring stiffness is discussed. Meanwhile, two factors affected soil spring stiffness, tunnel depth and soil Poisson's ratio, are also analyzed. It is shown that soil spring stiffness of shallow shield tunneling is different from that of deep shield tunneling, and the ratio of compression and shear spring stiffness varies along shallow shield tunneling. It is also found that the value and distribution law of soil spring stiffness of shallow shield tunneling greatly depend on tunnel depth and soil Poisson's ratio.     

Deformation Monitoring and Its Control in a Shallow buried Large span Tunnel Constructed Using the Pile Beam Arch Method

Deformation monitoring and control measures of a shallow buried large span tunnel constructed using the pile beam arch (PBA) method are described, taking the North Gongti Road Station of Beijing Metro line 10 as an example. Based on the monitoring datum, the crown settlement, convergence, ground settlement of the tunnel and the bridge foundation settlement are analyzed. The results show that (1) the PBA tunneling method can restrain the ground settlement and deformation of a shallow buried large span tunnel; (2) the depth, tunnel span and pilot tunnel construction may influence the deformation of a shallow buried large section tunnel significantly; and, (3) advanced conduit grouting, timely preliminary support and permanent lining construction can reduce the deformation effectively.     

A new method for calculating the vacancy formation energy of typical structure metals

Based on the model proposed by Tiwari and Patil, we improved the calculation method for surface energy, and calculated the vacancy formation energy for typical metals such as fcc, bcc and hcp metals. The calculated results and experimental values agree with each other when an energy modification coefficient is introduced. The energy modification coefficients of fcc, bcc and hcp metals are 1.292, 1.265 and 1.357, respectively. The proposed method can calculate and predict the vacancy formation energy of metals efficiently.     

Galerkin Boundary Element Method for Direct Boundary Integral Eqution for Dirichlet Problem of 2-D Laplace Eqation

The direct boundary integral equation of two-dimensional Laplace equation for Dirichlet problem is(con-sidered).It is deduced by Green's formula and the fundamental solution.The most-used numerical method for solving(direct) boundary integral equation is collocation method,and seldom have been used the Galerkin scheme in this case.The direct boundary integral eqution is changed into the variational eqution.Using linear element,it is solved by Galerkin boundary method.In the variational eqution double integrations shall be carried out.The paper presents the analytical formula to calculate the inner integration and the Gaussian quadrature is used for the outer integration. The numerical experimentation proved thefaesibility and the efficiency.     

辽宁陆面温度的反演与实测数据对比分析

为了及时准确地从遥感图像数据中反演出地表温度的变化,针对辽宁地区制定播种计划、确定种植结构等提供技术支持,选取辽宁省作为研究区,利用EOS/MODIS热红外遥感数据和FY-3/MERSI数据与相关的地面气象台站实测数据,建立地表温度反演模型。采用分裂窗算法中的两因素模型和普适单通道算法对辽宁省地表温度进行反演。通过对气象台站实测的地面温度值和反演的温度进行拟合来获取回归方程,再利用反演的温度值模拟真实地表温度。对比2种算法,得出分裂窗算法是更适合进行辽宁地区地表温度的反演方法。     

A Three-Dimensional Numerical Model and Experimental Research for U-Tube Ground Heat Exchanger in Heating Operation

In terms of the theory of a transient energy balance on the finite controlled volume, in this paper, a transient three-dimensional heat transfer model for the simulation of a single vertical U-tube ground heat exchanger based on finite-difference methods is systematically proposed. The model is also compared with experimental results during the heating operation in winter. What's more,based on test data and domestic and foreign literature, the equations to determine the undisturbed ground temperature for wet and heavy soil in Chongqing are presented. These formulae are essential conditions to calculate the heat transfer model.     

烟草Ⅰ型几丁质酶的生物信息学分析

旨在对烟草Ⅰ型几丁质酶进行生物信息学分析,了解其生物学特征,为下一步研究烟草Ⅰ型几丁质酶在烟草抗病过程中的作用奠定基础。采用生物信息学的方法,对已在NCBI 上登陆的烟草、拟南芥、水稻、菜豆的Ⅰ型几丁质酶(chitinase,ChiⅠ)氨基酸序列特征和进化关系进行了预测和分析。结果表明,这4 种植物Ⅰ型几丁质酶的分子量大小在28~37 kDa之间,均具有信号肽,结构域高度保守,均具有几丁质结合区(Cht BD1)和催化功能区(Glyco_hydro_19);烟草中的3 种Ⅰ型几丁质酶序列相似性较高,可以聚为一类;烟草与拟南芥和菜豆中的一种ChiⅠ遗传距离较近,而与水稻中ChiⅠ的遗传距离较远。通过分析发现,烟草Ⅰ型几丁质酶有着与其他植物中该酶相同的特性,为进一步研究烟草抗病蛋白提供理论依据。     

Numerical Simulation of Strata Movement Behavior in Deep Excavation

According to the complex conditions of deep excavation in Nantong mine, FLAC program are carried out for strata movement, ground pressure and surface displacement due to coal extraction. Based on the analysis of Nantong mine, the basic features of strata movement, the fundamental behavior of ground pressure and the related parameters of surface displacement are obtained. The results are of referential value for mining, supporting and preventing of surface displacement.     

水平荷载作用下斜坡刚性桩非线性分析

在综合分析现有水平荷载作用下桩基分析方法的基础上,建立了考虑桩侧土体受力状态的斜坡刚性桩力学模型;根据极限平衡原理,建立横向荷载作用下斜坡刚性桩弯矩和应力平衡方程;引入考虑斜坡影响的p-y曲线方法,提出了综合考虑桩侧土体极限承载力与水平抗力系数沿深度呈线性增加的侧向极限承载力与土体抗力承载力系数计算方法,同时,将该方法应用于计算实例,通过与已有有限元和理论计算方法对比分析,计算结果验证了本文方法的合理性与可行性;并利用该方法,分析了斜坡坡角、桩土接触面系数以及地基水平抗力系数对斜坡刚性桩承载特性的影响因素。分析表明:斜坡的坡角、桩土接触面系数对侧向荷载作用下斜坡刚性桩的荷载位移曲线影响明显,而桩侧土的抗力系数对侧向荷载作用下斜坡刚性桩的荷载位移曲线影响不明显。     

The Prognostication of the Effects of the Horizontal Drains on Lowering the Ground Water Table in Hill Slopes

This paper recommends a method of lowering the ground water table by setting up the horizontal drains in hill slopes.Based on the finite element analysis, the method advances the experiential formulation about the downstream water depth of the horizontal drains and the distance between the horizontal drains. The experimental result seems to agree reasonably well with the expression.So, in engineering practices,the formulation can be used to predict the amount of lowering of the downstream water depth, and also to confirm the distance between the horizontal drains.     

氮素营养对广宁红花油茶幼苗生长及光合特性的影响

为了探索不同N素供应水平对广宁红花油茶苗期生长以及光合生理特性的影响,设置每株0、1000、2000、3000、4000、5000 mg 6个施肥量处理（编号为Ⅰ~Ⅵ）,对广宁红花油茶幼苗进行N素指数施肥试验。每次施肥后都对油茶幼苗进行苗高、地径、生物量以及光合特性的测定,处理分析数据,来探究不同N素供应水平对其苗期生长、光合生理特性的影响。结果表明,N素指数施肥对植物的生长及光和特性有显著影响：（1）经指数施肥处理(Ⅱ~Ⅴ)的广宁红花油茶苗高均显著大于对照处理Ⅰ。其中,处理Ⅴ的苗高和地径最大,处理Ⅱ的生物量最大。从各处理间广宁红花油茶苗期生长表现的变化情况分析,各生长指标受N素影响的大小顺序：苗高＞生物量＞地径。（2）广宁红花油茶各施肥处理间光合生理特性指标有显著差异。净光合速率基本上都呈现出2次先增加后减小的趋势,随着N素施用量的增加,气孔导度2次呈现出先增加后逐渐减小的趋势,胞间CO2浓度和蒸腾速率由于受到气孔导度的影响,表现出与气孔导度相似的规律性变化。     

作物覆盖度的近地面测量方法综述

作物覆盖度是农业生态学、作物栽培学和水土保持学等学科中的重要研究参数,因此如何快速和准确地地获得覆盖度数据对相关科技工作者具有实用价值。本文综述了国内外的作物覆盖度的近地面观测方法,将其归纳为三大类：地面实测类、动态模型类和遥感类,提出并评估了利用叶面积指数推导作物覆盖度的模型法。同时,在分析各种方法的特点和优势的基础上,对不同情形下的覆盖度方法的使用提出建议,最后对作物覆盖度测量方法可能的发展与研究方向作出了展望。以期为相关研究人员快速获得适宜的观测方法和方案提供参考。     

辽宁省春季表层地温变化特征及其与气温的关系

为揭示春季地温对各气象因子的关系与响应程度,总结地温变化规律,以辽宁地区为研究区域,通过利用1981—2010年3—5月辽宁省49个气象站的地温、气温、日照时数、太阳辐射、平均风速、水汽压、相对湿度、降水逐日资料,采用气候倾向率、相关分析、回归分析、因子分析等统计方法研究了近30年辽宁地区地温变化趋势及其气象影响因素。结果表明：随土壤深度的增加,地温与气温的差值逐渐降低,辽宁中部地温与气温差值相对较小;辽宁西部地温>辽宁东部地温>辽宁地区气温;地温与8种气象因素特别是气温的关系更为紧密且有显著的正相关性。在春播期地温预报中,应结合地形地貌特点充分考虑这些气象要素带来的影响。     

Application of partial least squares regression in the forecast of ground subsidence

Taking into account many influence factors of ground subsidence induced by underground exploitation,based on partial least squares multinomial regression,a forecast analysis on the maximum of ground subsidence is carried out.Taking height,depth,obliquity of coal clay and rigidity coefficient as independent variables,and maximum of ground subsidence as dependent variable,the forecast model of maximum of ground subsidence is obtained.It is found that,Press residual value decreases with the increase of number of latent variables,and the number of latent variables is four by Press residual value versus number of latent variables.The normal regression coefficient of height is the largest in the four influence factors,and this indicates that the influence of height is the largest on maximum of ground subsidence.The determination coefficient of forecast model obtained in this paper is 0.915 7,the error of forecast model is ±10.41%.The following conclusion can be drawn that the model based on partial least squares multinomial regression is a better and feasible non linear method.     

The Technology of Grouting into Separated Strata in Overburden and Computational Model

After coal mined, the balance of original stress state is to be broken. In the course of retribution, displacement and deformation in the overburden takes place with the working face advancing. The article points out that overburden can be divided into, in ascending, caving zone, fractured zone, bending zone and loose alluvium zone. The extracting space can be prevented from transferring to ground with injection material into bed-separation gap. Applying both mining subsidence theory and elastic thin plate theory, the computational model of subsidence control technology of grouting is worked out. The model can get rid of blindness of determining the position of separated strata, forecast the surface subsidence and provide the basis of theory for forecasting surface subsidence control technology of grouting.     

FDM for Large Strain Consolidation of Multi-Layers Super Soft Ground

Follow in precursory relating documents, several equations of one dimension Large Strain Consolidation (LSC) and consolidation coefficients were discussed firstly. Based on this, a Finite Difference Method (FDM) equation was derived, which was the physical described LSC equation with variable displacement. Moreover, the initiate and boundary condition were dispersed by FDM, and the boundary of different layers of super soft soil was disposed of continuity. Finally,nonlinear group equations of LSC FDM solution was deduced for multi layers super soft ground by repeated method, and a FDM program of 1D nonlinear LSC analysis was compiled. Finally, a case showed a satisfied analysis result by LSCFDM.     

Fault Line Selection for the Distribution System with the Adjustable Arc Suppression Coil

The problem of the faulty line selection with the arc suppression coil(ASC) has existed for a long time.On the basis of analyzing the relationships between the ASC admittance and the admittances of lines,including the faulty line and non-faulty lines,the calculation of the b parameter is presented,in which the state of the ASC is changed during the single-ground existing for the faulty line selection by adjusting its inductance.The value of b for the faulty line is much greater than that for non-faulty lines in both the direct ground and the ground with the resistance.The proposed method is verified with the simulation and is applied to the projection.It is proven that the proposed method is with the high reliability.     

高粱挤压膨化工艺条件的研究

在单因素试验基础上,采用响应面分析法研究挤压工艺条件对高粱仁膨化特性的影响。结果表明,回归方程能较好地预测高粱膨化度随挤压工艺参数变化的规律,高粱挤压膨化的最佳工艺条件是:物料含水量25.5%,物料粒度60目,转速300 r/min,膨化温度164℃,膨化度3.22。