复合固化砂土力学及水稳性能试验研究

为探究经水泥、石灰和改性聚丙烯纤维复合固化砂土的力学及水稳性能,进行了系列室内试验,结果表明:随水泥掺量增加,固化砂土无侧限抗压强度和劈裂抗拉强度增大,但增长幅度减小,用一定量石灰取代水泥会降低水泥土强度,纤维可以提高水泥土强度,尤其是抗拉强度;水泥可大幅提高砂土抗剪强度和抗压回弹模量,随着纤维掺量的增加,固化土抗剪强度低于水泥土,黏聚力和回弹模量先增大后又减小,内摩擦角与黏聚力表现出负相关性;0.3%纤维加筋8%水泥固化土可以满足简易机场对基层材料的要求。     

复合固化砂土力学及水稳性能试验研究

为探究经水泥、石灰和改性聚丙烯纤维复合固化砂土的力学及水稳性能,进行了系列室内试验,结果表明:随水泥掺量增加,固化砂土无侧限抗压强度和劈裂抗拉强度增大,但增长幅度减小,用一定量石灰取代水泥会降低水泥土强度,纤维可以提高水泥土强度,尤其是抗拉强度;水泥可大幅提高砂土抗剪强度和抗压回弹模量,随着纤维掺量的增加,固化土抗剪强度低于水泥土,黏聚力和回弹模量先增大后又减小,内摩擦角与黏聚力表现出负相关性;0.3%纤维加筋8%水泥固化土可以满足简易机场对基层材料的要求。     

纳米SiO2改性滨海水泥土的短龄期力学性能与微观机制

为了研究纳米SiO₂对滨海水泥土短龄期的力学改性效果,开展了纳米SiO₂掺量（与水泥质量比）分别为0%、1.5%、3.0%、4.5%和6.0%的水泥土无侧限抗压试验、劈裂抗拉试验、pH试验、SEM试验。力学试验表明,纳米SiO₂能够提高水泥土的无侧限抗压强度、劈裂抗拉强度和弹性模量,但加剧了水泥土的脆性;纳米SiO₂改性水泥土的抗压强度大约为抗拉强度的10倍;pH测试表明,纳米SiO₂能够改善水泥土的碱性环境。SEM微观测试发现,水泥土颗粒形态、孔隙特征变化规律与强度发展规律关系紧密,随着纳米SiO₂掺量的增加,土颗粒形态分布由松散变为聚集,并伴随孔隙的减少。综上发现,纳米SiO₂掺量为4.5%时,强度改善效果最佳,微观孔隙最少,4.5%为最优掺量。最后,建立了纳米SiO₂改性水泥土力学强度与微观孔隙率之间的二次多项式模型。     

纤维聚苯乙烯泡沫颗粒轻质土的制备及力学性能

为促进轻质土在岩土工程中的广泛应用,添加改性聚丙烯纤维改善其力学性能,通过无侧限抗压强度试验分析探讨了纤维聚苯乙烯泡沫（EPS）颗粒轻质土强度-变形特性、受压破坏模式和无侧限抗压强度的影响因素,并运用SEM从微观层次上分析了其力学机制。结果表明:不同EPS颗粒、纤维及水泥掺量时,纤维EPS颗粒轻质土的应力-应变曲线不同;EPS和水泥掺量是强度的主要影响因素,其次为纤维掺量;强度随EPS掺量的增大而显著降低,随水泥掺量增大而显著提高;未加纤维的EPS颗粒轻质土松散且易破碎,强度骤然丧失;添加纤维能提高轻质土的峰值强度、残余强度、整体性和韧性,改善其脆性破坏模式;但EPS掺量较高（大于干土质量的3%）时,纤维与水泥土粘结有限,EPS颗粒轻质土力学性能改善效果较弱;EPS颗粒为空心蜂巢结构,纤维表面布满针状的水泥水化物并形成空间网状结构。所得结论表明纤维改善了轻质土力学性能。      

混杂纤维再生砖骨料混凝土正交试验及卷积神经网络预测分析

利用正交试验研究了再生骨料比例、混杂纤维比例以及减水剂掺量三个因素对混杂纤维再生砖骨料混凝土力学性能敏感性的影响,并利用卷积神经网络(CNN)对试验结果进行了预测分析和变参数扩展分析.结果表明:再生砖骨料(RBA)与再生混凝土骨料(RCA)的比例对混杂纤维再生砖骨料混凝土的抗压强度及劈裂抗拉强度的影响最大,其次是减水剂掺量,最后是玻璃纤维(GF)与聚丙烯纤维(PF)的比例.抗压强度及劈裂抗拉强度随着RBA与RCA的比例的减小而增大,随着减水剂掺量的增大而减小.本工作建立的CNN模型具有较高的预测精度,并且可以用于试验结果的变参数扩展分析.     

SG-1型土壤固化剂固化土的实验研究

实验采用自制SG-1固化剂对江苏滨海区盐渍土进行固化实验,并与水泥固化土进行了对比实验。考察了固化剂掺量及试件养护龄期对固化土无侧限抗压强度的影响,并在此基础上进行了固化土耐水性试验。结果表明,该固化剂掺量为10%时,固化土试件的7d抗压强度可达4.1MPa,水稳系数为0.80,均优于水泥固化土。随着养护龄期增长和固化剂掺量增加,抗压强度不断增大。采用XRD和SEM对SG-1固化剂固化土试件进行了表征,结果表明,SG-1型固化土中生成的钙矾石晶体填充了空隙,使固化土强度及耐水性增强。     

聚丙烯-钢纤维/混凝土柱大偏心受压承载力计算

对270个聚丙烯纤维掺量(体积分数)分别为0vol%、0.1vol%、0.2vol%、0.3vol%、0.4vol%、0.5vol%、钢纤维掺量(体积分数)分别为0vol%、0.5vol%、1vol%、1.5vol%、2vol%的聚丙烯-钢纤维/混凝土试块进行立方体抗压试验、轴心抗压试验和劈裂抗拉试验,基于复合材料力学理论,考虑纤维的取向系数、长度有效系数和界面黏结系数,对其建立强度预测模型并进行机制分析,同时选取掺量分别为0vol%、0.1vol%、0.3vol%的聚丙烯纤维、掺量分别为0vol%、1.5vol%的钢纤维制作6根聚丙烯-钢纤维/混凝土柱,对其进行大偏心受压试验,在强度预测模型的基础上进行承载力计算,提出聚丙烯-钢纤维/混凝土承载力计算方法。结果表明:钢纤维对聚丙烯-钢纤维/混凝土立方体抗压强度、轴心抗压强度和劈裂抗拉强度均有提高;聚丙烯纤维可提高聚丙烯-钢纤维/混凝土的劈裂抗拉强度,但不能提高聚丙烯-钢纤维/混凝土的抗压强度;聚丙烯-钢混杂纤维加入混凝土柱可有效提高其极限承载力。      

棉花秸秆水泥基砌块材料的基本力学性能

采用正交试验设计方法,以水泥和砂为基体相,以棉杆纤维为增强相,考虑棉花秸秆掺量、铝粉掺量及砂掺量三个因素在三个水平下的影响,配制植物纤维增强水泥基砌块,对立方体抗压强度和劈裂抗拉强度进行极差分析与方差分析;采用多元线性回归分析方法建立基于强度的棉花秸秆水泥基砌块材料配合比经验公式,结合砌块制作工艺,确定满足不同抗压强度等级棉花秸秆水泥基砌块材料的最优配合比。结果表明:棉花秸秆掺量是影响水泥基砌块材料抗压强度和劈裂抗拉强度的最主要因素,砂掺量次之,铝粉掺量影响程度最小;按照经验公式配制砌块的实测抗压强度与计算抗压强度吻合较好。     

太阳能光谱选择性吸收涂层研究进展

采用高速研磨搅拌加水掺法,制备出含不同质量分数的纳米SiO2混杂纤维（NSPF）混凝土,通过力学试验测得立方体抗压强度、劈裂抗拉强度、变形性能及冲击韧性。通过与钢纤维／聚丙烯二元混杂纤维（SPF）混凝土进行比较,NSPF混凝土的立方体抗压强度、劈裂抗拉强度、疲劳次数、弹性模量、初裂抗冲击次数和破坏抗冲击次数分别提高10...     

钢纤维和碳纤维的混合效应对高性能混凝土力学性能的影响

通过在混凝土基体中加入一种纤维和混合纤维,制备了高性能混凝土试件和混合纤维高性能混凝土试件。通过劈裂抗拉强度试验和落锤冲击试验,研究了单掺钢纤维、单掺碳纤维和混合纤维对高性能混凝土试件劈裂抗拉强度和抗冲击性能的影响,分析了混合效应对试件力学性能的增强作用。劈裂抗拉强度试验结果表明,只掺入碳纤维,且碳纤维掺入量为1%时,试样劈裂抗拉强度的提升系数最多增加了50%;只掺入钢纤维时,钢纤维的掺入量越多,试样劈裂抗拉强度的提升系数越小,而且减小了基体高性能混凝土的劈裂抗拉强度;当钢纤维掺量为4.0%、碳纤维掺量为0.5%时,试样的混合效应系数最大为1.35,此时产生正混合效应,提升了高性能混凝土试样的劈裂抗拉强度。抗冲击性能试验结果表明,单掺碳纤维减弱了高性能混凝土试件的抗压强度,单掺钢纤维虽然可以加强试件的抗压强度但试件的延性比提升率不高,而混合纤维比单一纤维有优势,更能够增强高性能混凝土试件的抗冲击性能。因此,钢纤维与碳纤维的混合效应提升了试件的劈裂抗拉强度与抗冲击性能,明显提升了高性能混凝土的力学性能。     

机场道面抢修用聚氨酯稳定集料的试验研究

以机场道面意外损毁的抢修为目的，进行了聚氨酯发泡快速稳定道面基层回填料的试验研究。试验结果表明，常温下用聚氨酯发泡稳定碎石集料，2h无侧限抗压强度达到2．05MPa，对道面结构的有限元分析表明，试验所用材料可满足道面基层的力学性能要求。     

改进相位编组直线算法提取遥感图像中的机场目标

本文在分析了机场影像的重要特征之后,改进了相位编组直线提取算法,在机场跑道检测中,利用改进算法精确提取出跑道平行直线对,然后采用区域生长算法确定机场的整个结构。实验证明,这种改进的算法具有更好的抗噪性能,对于影像质量要求有更加宽松的范围,更具有实用性能。     

机场内部飞机噪声监测与评价

对某军用机场内部噪声环境影响进行评价,机场内部布设七个位置点进行噪声测量,在实际监测的基础上,采用计权等效连续感觉噪声级和A计权声级的最大值为评价量对机场飞机噪声现状进行评价,同时介绍了机场内部飞机噪声污染的危害及应采取的相关防治措施.     

机场内部飞机噪声影响评价与防治方法研究

军用喷气式飞机噪声危害显著，机场内部是受到飞机噪声危害最为严重的区域，但长期以来一直没有得到人们的重视。根据飞机噪声影响的特点，提出了一种基于双指标的机场内部飞机噪声评价方法。并在此基础上，结合噪声等值线图，提出机场内部飞机噪声防治的方法。结合某机场，具体分析了机场内部飞机噪声现状影响评价方法和机场飞机噪声的防治方法与步骤。     

Estimating fatigue endurance limits of flexible airfield pavements

In perpetual pavements, damage from bottom-up cracking can be limited to the top surface lift through using a very thick surface layer or a binder-rich intermediate layer. This can be attained by maintaining tensile strains at the bottom of the hot-mix asphalt (HMA) layer below a certain value known as the fatigue endurance limit (FEL). This paper presents a method for estimating a strain-based FEL for flexible airfield pavements. The proposed method is based on the concept that a 50% reduction in HMA layer modulus would indicate initiation of fatigue cracking. Falling weight deflectometer (FWD) testing results, collected from National Airport Pavement Test Facility (NAPTF) flexible pavement sections, were analyzed to determine at which loading pass each section had a 50% reduction in HMA layer modulus (N_f50). NAPTF tensile strain data were also used to determine the tensile strain at N_f50 for each pavement section by averaging the peak tensile strains. The proposed approach was validated by comparing its results to those obtained using a common FEL estimation model known as the rate of dissipated energy change (RDEC) model. To further verify the results of the proposed approach, peak tensile strain was plotted vs. number of loading cycles for all sensors. Using these plots, the peak tensile strain at which the variability in the strain gauge data increased was used as an estimate of a possible FEL. The N_f50 tensile strains estimated using the proposed method were comparable to the values determined from RDEC and variability approaches.     

Expedient airfield runway repair using folded fibreglass mat

For expedient airfield runway repair, the US Air Force has developed a folded fibreglass mat to cover craters repaired with a well-compacted granular base material. The objective of this study was to evaluate the adequacy of using polymer plugs to anchor the mat to a repaired asphalt pavement for heavy aircraft operations. The effort consisted of materials testing, field experiments and analytical modelling. An 89,800-kg (198,000-pound) load cart having the footprint of a single C-5 main gear was pulled on a mat with wheels locked to simulate full braking forces. Anchor bushings were instrumented to measure anchor loads. A simplified numerical model was developed for anchor load analysis which has been validated against the load cart test data. The anchor system sustained the braking forces from all the load cart tests without failure. The polymer plug anchors have adequate vertical pull-out capacity to resist the uplifting force from the ‘bow wave’ formation of the mat. The polymer plug anchors also have adequate resistance to fatigue loads.     

Oil-Shale Fly Ash Utilization as Independent Binder of Natural Clayey Soils for Road and Airfield Base Construction

ABSTRACT

This article describes physicochemical interactions of different natural clayey soils with oil-shale fly ash (OSFA) from thermal power plants, dealing with the strengthening processes of new materials. Toward this end, a range of traditional and modern research methods were used, i.e., definition of the ultimate strength under uniaxial compression and rupture by the Brazilian method, temporary changes in moisture content and linear deformation, water and frost resistance, free CaO and SO₃, CaCO₃, XRD, and SEM. It was established that the surfaces of the initial component (OSFA and soils) particles were dissolved in porous alkaline solutions. The dissolution products gave rise to new amorphous and crystal formations. After 28 days, the strength of the samples reached 2–12 MPa but, after 90 days, it rose to 4–31 MPa. It was found that the strength at every stage of hardening can be increased significantly by changing the proportion of the initial mixture's composition. The materials displayed very high water and frost resistance, with coefficients equaling or exceeding the 1.0 level, except the OFSA and loess combination. The materials developed are applicable for the construction of roads, airfields, and dam bases and for various types of foundations without traditional binders, such as cement, and without heating.     

Oil-Shale Fly Ash Utilization as Independent Binder of Natural Clayey Soils for Road and Airfield Base Construction

This article describes physicochemical interactions of different natural clayey soils with oil-shale fly ash (OSFA) from thermal power plants, dealing with the strengthening processes of new materials. Toward this end, a range of traditional and modern research methods were used, i.e., definition of the ultimate strength under uniaxial compression and rupture by the Brazilian method, temporary changes in moisture content and linear deformation, water and frost resistance, free CaO and SO₃, CaCO₃, XRD, and SEM. It was established that the surfaces of the initial component (OSFA and soils) particles were dissolved in porous alkaline solutions. The dissolution products gave rise to new amorphous and crystal formations. After 28 days, the strength of the samples reached 2-12 MPa but, after 90 days, it rose to 4-31 MPa. It was found that the strength at every stage of hardening can be increased significantly by changing the proportion of the initial mixture's composition. The materials displayed very high water and frost resistance, with coefficients equaling or exceeding the 1.0 level, except the OFSA and loess combination. The materials developed are applicable for the construction of roads, airfields, and dam bases and for various types of foundations without traditional binders, such as cement, and without heating.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.