Anisotropy Effects on Microseismic Event Location

Seismic anisotropy in sedimentary environments is significant—microseismic waveforms often show strong shear-wave splitting, with differences reaching 40% between horizontally and vertically-polarized shear-wave velocities. Failure to account for this anisotropy is shown to result in large microseismic event location errors. A method is presented here for determining the five elastic parameters of a homogeneous, vertical transverse-isotropic (VTI) model from calibration shot data. The method can also use data from mining-induced seismic events, which are then simultaneously located. This simple model provides a good fit to arrival times from coal-environment data, and results in dramatic shifts in interpreted event locations.     

2006年4月11—12日寒潮天气成因

利用天气图和数值预报产品，对2006年4月11—12日河南省寒潮天气过程的环流形势、单站气象要素变化及成因等进行了分析，结果表明：500hPa横槽转竖是寒潮天气产生的重要影响系统；850hPa冷平流是强降温的主要原因。     

A transversely isotropic thermo-poroelastic model for claystone: parameter identification and application to a 3D underground structure

A transversely isotropic thermo-poroelastic constitutive law is developed and implemented in the finite element code Code_Aster (EDF, France). It is then validated using an analytic solution for an inclined borehole in a transversely isotropic medium. A strategy for identifying the parameters of the transversely isotropic thermo-poroelastic model based on an inverse method is proposed on the basis of different laboratory tests. To demonstrate the efficiency and applicability of the model, it is then applied in a three-dimensional numerical model of an underground structure in a parameter sensitivity study. The results of the modelling highlight the importance of accounting for anisotropic phenomena when determining the dimensions of underground facilities. The whole approach is presented in the paper, from model development to application to 3D numerical modelling to an engineering case study.     

Study on frost resistance of rapid-hardening magnesium phosphate-ferro-aluminate composite cement北大核心CSCD

随着冬季抢修抢建混凝土工程的增多,研发适用于严寒地区具有良好抗冻性的快硬水泥意义重大。磷酸镁水泥具有早期强度高、初凝时间短、与混凝土相容性好等特点,被视为混凝土工程的良好快修快建材料。然而,磷酸镁水泥制备的水泥砂浆或混凝土在北方地区的冬季往往会受到冻融循环作用,导致其耐久性和强度出现不同程度的退化。为增强磷酸镁水泥的抗冻性,在磷酸镁水泥制备中用铁铝酸盐水泥代替一定数量的过烧氧化镁,制备出快硬磷酸镁-铁铝酸盐复合水泥。通过冻融循环前后磷酸镁-铁铝酸盐复合水泥砂浆试件的质量损失测试、强度试验、孔隙率测试及SEM-EDS测试,得出：铁铝酸盐水泥代替氧化镁的数量在30%~40%时,制备的磷酸镁-铁铝酸盐复合水泥砂浆试件冻融循环后的质量损失率最小,抗压强度和抗折强度达到峰值,抗压强度和抗折强度剩余率最高,孔隙率最小,因而该配合比的磷酸镁-铁铝酸盐复合水泥具有最好的抗冻性。由SEM-EDS测试可知磷酸镁水泥砂浆试件冻融循环后,基体中的胶凝材料K-鸟粪石部分溶解,试件整体结构疏松,晶体间存在大量间隙;磷酸镁水泥制备中掺入铁铝酸盐水泥后,制得的磷酸镁-铁铝酸盐复合水泥水化生成大量晶体填充于砂浆试件基体内部,无定形水化产物对砂浆试件的强度有一定补偿作用,使得磷酸镁-铁铝酸盐复合水泥砂浆试件在冻融循环后孔隙率大幅减小,密实度得到提高,使得磷酸镁-铁铝酸盐复合水泥的抗冻性能得到了显著增强。磷酸镁-铁铝酸盐复合水泥为北方严寒地区冬季混凝土抢修抢建工程提供了一种新材料。     

细砂中钢带-填土废塑料瓶抗拔性能试验研究

研究利用填土废塑料瓶作为横向构件附在加筋土挡墙（MSEWs）中钢带上可行性。配筋中的横向构件对增加抗拔力有重要影响。该加筋系统是由作为纵向构件的钢带和作为横向构件的填土废塑料瓶组成。为更好地研究以填土废塑料瓶作为横向构件对抗拔性能的影响,对一条独立的钢带和分别带有1～7个瓶子的钢带进行了拉拔试验。在不同的法向应力下进行了超过18次的实验室大型拉拔试验（例如拉拔箱尺寸为长1.2 m、宽0.6 m、高1.0 m）来评估新提出的加固元件的性能。试验结果表明,在扁钢带上建立三维空间对提高抗拔阻力影响很大。提高抗拔阻力最有效的方法是在距离S与直径D之比为3的钢带上加入4个横向构件,其平均抗拔阻力约为单独钢带的5倍。有横向构件和无横向构件钢带的极限抗拔阻力随竖向应力的增大而增大。     

钢纤维煤矸石混凝土抗冻性能及损伤模型研究

为研究钢纤维煤矸石混凝土的抗冻性能,以冻融循环次数和钢纤维掺量为主要变量,通过快速冻融试验,研究不同掺量的钢纤维煤矸石混凝土的表观形貌、质量损失、相对动弹性模量和抗压强度的变化规律;并依据钢纤维煤矸石混凝土动弹性模量的变化,定义钢纤维煤矸石混凝土的损伤变量,建立冻融环境下钢纤维煤矸石混凝土的损伤模型。研究结果表明：在冻融环境作用下掺入适量的钢纤维能够降低煤矸石混凝土的质量损失和减缓相对动弹性模量的下降,提高煤矸石混凝土的抗冻性能;依据损伤变量提出的损伤模型与试验数据符合较好,可以为冻融环境下钢纤维煤矸石混凝土的耐久性研究提供理论参考。     

Structural analysis and design of frost resistance function for subgrade of high-speed railway ballasted track in cold regions

According to the technical characteristics of short fixed wheelbase of a high-speed carriage, a subgrade-track integrated space mechanical response analysis model is proposed for trains under the action of biaxial load after the comparison of the stress distribution characteristics of the ballast track subgrade bed structures for high-speed railway under the action of uniaxial load and biaxial load. The loading threshold value (high-cycle long-term dynamic strength) under the circumstance where the cumulative deformation of subgrade structure gradually develops and finally reaches the convergent state, and its relationship with the foundation coefficient K₃₀ were deduced, based on the characteristics of cumulative deformation evolution obtained from the unit structure filling model test under the action of cyclic loading. In view of structure stability and frost resistance requirements of the railway subgrade in cold regions, technical conditions to maintain good service performance of subgrade structure of high-speed railway ballasted track are discussed and analyzed. Study results show that the additive effect manifests itself obviously for railway train bogies under the action of biaxial load than uniaxial load, which has a significant dynamic effect on the subgrade bed bottom and a slight effect on the surface layer. Thus, the adoption of a biaxial load model in the design of a high-speed railway subgrade accurately reflects the vehicle load. Pursuant to the structure design principle, the design method of the subgrade structure of high-speed railway ballasted track is proposed to meet the technical requirements such as structural strength, bearing stiffness and high-cyclic and long-term stability. Technical indicators are obtained for the variation of thickness of the surface layer of reinforced subgrade bed in the double-layer subgrade mode along with the change of K₃₀ at the subgrade bed bottom. The double-layer structure mode of "closure on the upper layer and drainage on the lower layer" was proposed in order to meet the waterproofing and drainage requirements of the upper layer of the subgrade bed in cold regions. A dense-framework graded gravel filler with weak water permeability at a coefficient of 10^-4 cm/s is used on the upper layer and the void-framework graded gravel filler at the water permeability coefficient of 10^-2 cm/s is adopted on the lower layer.     

电源及负载电阻对PTB220型气压传感器检定结果的影响

为保证检定结果的准确可靠,对多台自动气象站用PTB220型气压传感器进行了供电电压及负载电阻的试验。试验结果表明:在12~30V的范围内,随着供电电压的提高,PTB220型气压传感器模拟量输出测量误差存在着逐渐变大的现象,这种变化最大达到了-0.28hPa;而数字量输出则不存在这一问题;当负载电阻在10~500kΩ之间变化时,PTB220型气压传感器的模拟量输出测量误差在测量范围下限附近呈现出随着负载电阻的增加而逐渐增大的现象。基于这一发现,对PTB220型气压传感器检定方法的完善提出了针对性建议。     

海普诺改善HepG2 细胞胰岛素抵抗作用研究

通过细胞形态观察和CCK-8法研究HPN对HepG2细胞活力的影响。采用高糖高浓度胰岛素持续作用诱导Hep G2细胞建立胰岛素抵抗细胞模型,用多功能自动生化仪葡萄糖-己糖激酶法检测海普诺(HPN)对正常Hep G2细胞及胰岛素抵抗Hep G2细胞葡萄糖消耗量的影响。实验结果显示,低浓度的HPN对Hep G2细胞增殖没有影响。HPN与胰岛素协同作用Hep G2细胞,低浓度胰岛素对葡萄糖利用有一定的促进作用;当胰岛素浓度为1×10–6 mol/L时,HPN可明显促进Hep G2细胞葡萄糖消耗。进一步研究表明,HPN在5×10–8~1×10–7 mol/L浓度范围内可明显促进胰岛素抵抗Hep G2细胞的葡萄糖的消耗。HPN可明显改善Hep G2细胞胰岛素抵抗。     

Consolidation by vertical drains under time‐dependent loading

A solution for the consolidation by vertical drains under time‐dependent loading is presented in this paper. Considering the well resistance and the smear action, the simultaneous basic partial differential equations of the consolidation by vertical drains are obtained for the arbitrary loading method. However, the impulse function method cannot be directly applied to obtain the solution. The partial differential equations and the solution conditions that satisfy the impulse function method are obtained after some mathematical processing. The solution for the consolidation by vertical drains under time‐dependent loading is obtained by virtue of the impulse function method and the solution under instantaneous loading. The solutions under single ramp loading and multi‐ramp loading are obtained and the feasibility of Carrillo's method under time‐dependent loading is discussed. Further, the characteristics of the consolidation by vertical drains under instantaneous loading and time‐dependent loading are discussed. Copyright © 2000 John Wiley & Sons, Ltd.