抗侧压稳定性对塔机起重钢丝绳性能的影响

塔机起重钢丝绳具有缠绕层数多、起重高度大、起重速度快等特性,导致塔机起重钢丝绳失效的主要表现形式有磨损、疲劳及变形。分析钢丝绳横向受力状态,建议除了按标准对钢丝绳进行常规试验外,还应对其抗侧压稳定性进行测定。依据ISO 16839标准要求,对几种常用塔机起重钢丝绳进行抗侧压稳定性试验,得出相应数据。这些数据有利于为设备生产厂家合理设计工况与科学选择钢丝绳提供依据,延长塔机起重钢丝绳的使用寿命。

套管抗侧压与光缆性能关系的研究

光缆生产中,对松套管抗侧压性能的监测和分析已成为光缆生产过程控制的一项重要的质量监控手段,通过各种工艺手段以获得稳定的松套管抗侧压性能,不仅能够确保松套管本身的尺寸参数和性能符合要求,也有力地保障了后道工序生产过程中的质量稳定。

基于输电线路的钢管桩基础抗侧压装置设计研究

在此研究的输电线路改装置是在原设计钢管桩基础上,外侧长、宽、高分别增加的钢筋混凝土块。针对淤泥质地质,无法抵抗钢管桩基础所受侧压力后的变形。研究设计表明,设置该装置后,能够有效加强其抗侧压能力,堆土的侧压力对钢管桩基础几乎没有影响,极大地降低了施工成本。

钻井井壁可缩性接头模型试验研究

针对新型竖向可缩性钻井井壁 ,提出了两种可缩性接头结构形式 ,并进行了竖向、侧向和三轴加载模型试验 .研究结果表明 ,两种结构形式的可缩性接头均具有良好的竖向变形特性 ,抗侧压能力大 ,防水性能好 .

光缆结构与压扁冲击性能初探

本文通过试验和力学分析,对各种结构光缆的抗压扁与抗冲击性能进行了初步研究,给出了不同光缆结构的对比试验结果。并结合光缆结构的设计,提出了对光缆压扁冲击性能影响较大的因素,以及一些解决方案。

Effect of chloride salt concentration on unconfined compression strength of cement-treated Lianyungang soft marine clay

This study aims to quantify the influence of the amount of cement and chloride salt on the unconfined compression strength （UCS） of Lianyungang marine clay. The clays with various sodium chloride salt concentrations were prepared artificially and stabilized by ordinary Portland cement with various contents. A series of UCS tests of cement stabilized clay specimen after 28 d curing were carried out. The results indicate that the increase of salt concentration results in the decrease in the UCS of cement-treated soil. The negative effect of salt concentration on the strength of cement stabilized clay directly relates to the cement content and salt concentration. The porosity-salt concentration/cement content ratio is a fundamental parameter for assessing the UCS of cement-treated salt-rich clay. An empirical prediction model of UCS is also proposed to take into account the effect of salt concentration. The findings of this study can be referenced for the stabilization improvement of chloride slat- rich soft clay.

Determination and Evaluation of Strength Characteristics of Dry Jet Mixing

Dry jet mixing (DJM) for soft soil stabilization has been widely used since 1980s. The quality and strength of stabilized columns are fundamental parameters to evaluate the stabilization work. This paper presents the standard penetration test (SPT) method and its test results on cement columns. It is shown that SPT is an effective and simple method for inspecting and evaluating cement columns. The strength characteristics along the length of the column, a good correction between SPT blow count and the unconfined compressive strength are achieved.

色母料添加比例对光缆套管的影响

随着光纤网络通信的发展,光缆正在逐步替代同轴线缆。由于光缆施工接续的需要,光缆松套管需要用颜色标识。生产松套管作为光缆生产的关键工序,通过色母料的添加来改变颜色。PBT与色母料的比例影响套管的抗侧压力值和松套管余长。本文阐述不同比例的色母料添加对松套管的抗侧压力值和松套管余长的影响,为套管生产工艺提出个人的看法,为松套管的生产工艺控制提供一些的借鉴意义。

超长水池结构引发缝施工技术优化研究

目前我国在污水处理厂建设过程中,常发生因水池引发缝处施工质量问题而导致的污水泄漏事件。污水一旦泄漏将会对土壤、地下水环境产生严重影响,进而影响周边居民生活及城市生态环境。本文重点阐述了超长水池结构引发缝处的施工措施优化,总结了关键施工工艺和技术要点,为提高引发缝结构施工质量提供参考依据。

洞悉光缆生产套管PBT材料综合成本探究

本文以光缆用PBT材料为例.就不同厂家不同单位成本PBT满足套管抗侧压数值≥800N前提下,其套管单位材料成本、质量性能、生产成本多方面深入剖析,其目的在于单位材料消耗满足企业标准,为客户提供质量合格产品,同时缩减各种分摊制造成本,对于促进光缆制造行业原材料消耗成本分析提供一定借鉴意义。

Mechanical properties of fiber and cement reinforced heavy metal-contaminated soils as roadbed filling

The treatment of contaminated soil is a crucial issue in geotechnical and environmental engineering.This study proposes to incorporate appropriate polypropylene fibers and cements as an effective method to treat heavy metal contaminated soil(HMCS).The objective of this paper is to investigate the effects of fiber content,fiber length,cement content,curing time,heavy metal types and concentration on the mechanical properties of soils.To this end,a series of direct shear test,unconfined compression strength(UCS)test,dry-wet cycle and freeze-thaw cycle test are performed.The results confirm that the appropriate reinforcement of polypropylene fibers and cement is an effective way to recycle HMCS as substitutable fillers in roadbed,which exhibits benefits in environment and economy development.

Stabilization of saline silty sand using lime and micro silica

Many construction and post-construction problems have been reported in the literature when saline soils have been used without understanding of their abnormal behavior,especially their inferior bearing capacity in the natural condition.The strength of these soils further decreases on soaking.Saline soil deposits cover extensive areas in central Iran and are associated with geotechnical problems such as excessive differential settlement,susceptibility to strength loss and collapse upon wetting.Because of these characteristics,some of the roads constructed on saline soils in Taleghan area have exhibited deterioration in the form of raveling,cracking and landslides.The main objective of this work is to improve the load-bearing capacity of pavements constructed on Taleghan saline soils using lime and micro silica.Soil samples from Hashtgerd-Taleghan road were collected and tested for improving their properties using lime and micro silica at different dosages ranging from 0 to 6%.The load-bearing capacity of stabilized soil mixtures was evaluated using California Bearing Ratio(CBR) and unconfined compressive strength tests.The test results indicate that the lime improves the performance of soil significantly.The addition of 2% lime with 3% micro silica has satisfied the strength-deformation requirements.Therefore,improved soil can be used as a good subbase in flexible pavements.

Effect of polypropylene fiber and coarse aggregate on the ductility and fluidity of cemented tailings backfill

Adding polypropylene(PP)fibers and coarse aggregates has become a popular way to enhance the strength and stability of the cemented tailings backfilling(CTB)body.It is essential to explore the influence of tailings-aggregate ratio and fiber content on the mechanical properties of CTB samples.The comprehensive tests of the unconfined compressive strength(UCS),slump and microstructure were designed,and the regression models were established to characterize the effect of the strength,ductility and fluidity.The results indicate that the tailings-aggregate ratio of 5:5 and PP fiber content of 0.5 kg/m^(3) are the optimum point considering the UCS,cracking strain,peak strain and post-peak ductility.The tailings-aggregate ratio is consistent with the unary quadratic to the UCS and a linear model with a negative slope to the slump.Microstructural analysis indicates that PP fiber tends to bridge the cracks and rod-mill sand to serve as the skeleton of the paste matrix,which can enhance the compactness and improve the ductility of the CTB.The results presented here are of great significance to the understanding and application of coarse aggregates and fibers to improve the mechanical properties of CTB.

Key parameters controlling electrical resistivity and strength of cement treated soils

The improvement of question soils with cement shows great technical, economic and environmental advantages. And interest in introducing electrical resistivity measurement to assess the quality of cement treated soils has increased markedly recently due to its economical, non-destructive, and relatively non-invasive advantages. This work aims to quantify the effect of cement content （aw）, porosity （nt）, and curing time（T） on the electrical resistivity （p） and unconfined compression strength （UCS） of cement treated soil. A series of electrical resistivity tests and UCS tests of cement treated soil specimen after various curing periods were carried out. A modified Archie empirical law was proposed taking into account the effect of cement content and curing period on the electrical resistivity of cement treated soil. The results show that nt/（aw·T） and nt/（aw·T^1/2） ratio are appropriate parameters to assess electrical resistivity and UCS of cement treated soil, respectively. Finally, the relationship between UCS and electrical resistivity was also established.

Prediction of uniaxial compressive strength and modulus of elasticity for Travertine samples using regression and artificial neural networks

Uniaxial Compressive Strength (UCS) and modulus of elasticity (E) are the most important rock parameters required and determined for rock mechanical studies in most civil and mining projects. In this study, two mathematical methods, regression analysis and Artificial Neural Networks (ANNs), were used to predict the uniaxial compressive strength and modulus of elasticity. The P-wave velocity, the point load index, the Schmidt hammer rebound number and porosity were used as inputs for both meth-ods. The regression equations show that the relationship between P-wave velocity, point load index, Schmidt hammer rebound number and the porosity input sets with uniaxial compressive strength and modulus of elasticity under conditions of linear rela-tions obtained coefficients of determination of (R2) of 0.64 and 0.56, respectively. ANNs were used to improve the regression re-sults. The generalized regression and feed forward neural networks with two outputs (UCS and E) improved the coefficients of determination to more acceptable levels of 0.86 and 0.92 for UCS and to 0.77 and 0.82 for E. The results show that the proposed ANN methods could be applied as a new acceptable method for the prediction of uniaxial compressive strength and modulus of elasticity of intact rocks.

Estimation of jet grouting parameters in Shahriar dam,Iran

Jet grouting is a method for improving of soil and its physical characteristics.However,in this method,grouting of cement slurry with high pressure and velocity may cause damaging to soil structure,and then excavated grains of soil are removed from the borehole and replaced with cement slurry.The grains,which are remained around the borehole,mixed with slurry（cement） in-situ,can create an improved mass of soil.This mass is named＂Soilcrete＂.Soilcrete mass has special characteristics such as high strength,low deformability and very low permeability.In this paper,principles of jet grouting and effective parameters have been analyzed.Then the test results obtained from Soilcrete column have been investigated.Finally,the paper concludes with presenting amount of principle jet grouting parameters at foundation of Shahriar dam according to the results of jet grouting test.Based on the measurements,the diameter,Soilcrete UCS（uniaxial compression strength）,amount of the water,grout and air pressure and lifting and rotating speed in original site of jet grouting are 1.2～1.5 m,2～3 MPa,370～390 bar,10～15 bar,6～8 bar,7～8 cm/min and 7～8 cm/min,respectively.Also it can be seen that while the column diameter falls within the upper half of the range,some values of the compressive strength are close to the lower limit of the range.

Strength characteristics of modified polypropylene fiber and cement-reinforced loess

The reinforcement and stabilization of loess soil are duscussed by using fibers as the reinforcement and cement as the stabilization materials.To study the strength characteristics of loess soil reinforced by modified polypropylene(MPP) fiber and cement,samples were prepared with six different fiber contents,three different cement contents,three different curing periods and three kinds of fiber length.The samples were tested under submergence and non-submergence conditions for the unconfined compressive strength(UCS),the splitting tensile strength and the compressive resilient modulus.The results indicated that combined reinforcement by PP fiber and cement could significantly improve the early strength of loess to 3.65–5.99 MPa in three days.With an increase in cement content,the specimens exhibited brittle fracture.However,the addition of fibers gradually modified the mode of fracture from brittle to ductile to plastic.The optimal dosage of fiber to reinforce loess was in the range of 0.3%–0.45% and the optimum fiber length was 12 mm,for which the unconfined compressive strength and tensile strength reached their maxima.Based on the analysis of failure properties,cement-reinforced loess specimens were susceptible to brittle damage under pressure,and the effect of modified polypropylene fiber as the connecting "bridge" could help the specimens achieve a satisfactory level of ductility when under pressure.

Analysis of influence factors of unconfined compressive strength for composite soil stabilizer-stabilized gravel soil

In order to investigate the effect o f some factors on the unconfined compressive strength(UCS)for composite soil stabilizer-stabilized gravel soil(CSSSGS),the orthogonal test is adopted to set up the experimental scheme.Three levels o f each factor armconsidered to obtain the change laws o f UCS,in which the binder dosages are8%,10%,and12%;the curing times ae7,14and21d;the gradation nae0.3,0.35and0.4;and the degrees of compaction are95%,97%,and99%.The range analysis clearly indicates that the influence degree o f the four factors on UCS is in such an order:dosage,age,gradation,and degree o f compaction.The variance analysis shows that only the composite soil stabilizer dosage can significantly affect UCS.In road construction,the examination o f composite soil stabilizer dosage and base-course maintenance should be given much more attention to obtain satisfactory base-course strength,compared w ith gradation floating and the change of degree o f compaction.

Effect of cyclic drying and wetting on engineering properties of heavy metal contaminated soils solidified/stabilized with fly ash

Solidification/stabilization （S/S） is one of the most effective methods of dealing with heavy metal contaminated soils. The effects of cyclic wetting and drying on solidified/stabilized contaminated soils were investigated. A series of test program, unconfined compressive strength （UCS） test, TCLP leaching test and scanning electron microscopy （SEM） test, were performed on lead and zinc contaminated soils solidified/stabilized by fly ash. Test results show that UCS and the leaching characteristics of heavy metal ions of S/S contaminated soils are significantly improved with the increase of fly ash content. UCS of S/S soils firstly increases with the increase of the times of drying and wetting cycles, after reaching the peak, it decreases with it. When the pollutant content is lower （1 000 mg/kg）, the TCLP concentration first slightly decreases under cyclic drying and wetting, then increases, but the change is minor. The TCLP concentration is higher under a high pollutant content of 5 000 mg/kg, and increases with the increase of the times of drying and wetting cycles. The results of scanning electron microscopy （SEM） test are consistent with UCS tests and TCLP leaching tests, which reveals the micro-mechanism of the variations of engineering properties of stabilized contaminated soils after drying and wetting cycles.

Effect of aggressive pH media on peat treated by cement and sodium silicate grout

The effects of aggressive peat nature (pH) on the strength of peat treated by cement and cement-sodium silicate grout were investigated by evaluating the changes in unconfined compressive strength,moisture content,and scanning electron microscopy (SEM) of samples with time in different pH media.The results indicate that peats treated by cement-silicate have higher strength than peats treated by cement,due to an increase in pH value of the media.Furthermore,cement and cement-silicate are highly effective in reducing the moisture content and void ratio of the treated peats.The microstructures of treated peats support the laboratory test results.