浅谈辊压法木材防护浸注技术

简述了国内外木材浸注技术的最新研究进展;重点论述了木材防护浸注厅法--辊压法,讨论了辊压法的浸注原理,以及与传统木材浸注方法--真空加压法在设备、工艺方面的比较,明确了控制压缩率的重要作用,并尝试应用计算机图像处理技术测量计算木材体积空隙率来确定压缩率,建议辊压浸注处理大青杨时,压缩率可试取50％及以下。     

Assessing the compaction susceptibility of South African forestry soils. II. Soil properties affecting compactibility and compressibility

Factors affecting the compaction susceptibility of South African forestry soils were assessed. Two traditional measures of compaction susceptibility were used: maximum bulk density (ρ_mbd) determined by the standard Proctor test, defined compactibility, and the compression index using a simple uni-axial test, defined compressibility. Soils were chosen from a broad range of geological and climatic regions and they varied greatly in texture (8 to 66 g 100 g⁻¹ clay) and organic matter content (0.26 to 5.77 g 100 g⁻¹ organic carbon). Soils showed a wide range in ρ_mbd values, from 1.24 to 2.00 Mg m⁻³, and this reflected the wide range of particle size distributions and organic matter contents of the soils. Very good correlations were achieved between measures of particle size distribution, particularly clay plus silt and both compactibility and compressibility. Both compactibility and compressibility were significantly correlated with loss-on-ignition (L_OI) which is a measure reflecting the combined effects of soil texture and organic matter on soil physical properties. Indices of compaction susceptibility were influenced more by particle size distribution than by organic carbon content. Clear effects of organic carbon on compaction behaviour were only evident for soils with low clay contents (< 25 g 100 g⁻¹. No clear relationship between compactibility and compressibility was found. Compactibility generally increased with decreasing clay plus silt content, whereas compressibility increased up to about 70 g 100 g⁻¹ clay plus silt before decreasing again. It is difficult to define compaction susceptibility solely in terms of indices of compactibility or compressibility particularly as there is no clear relationship between these two properties. A classification system for compaction risk assessment is presented, based on the relationship between compactibility (ρ_mbd) and L_OI, and between clay plus silt content and compressibility.     

揉碎玉米秸秆可压缩性研究

揉碎玉米秸秆的可压缩性对压缩工艺的优化、压缩设备的研制、压缩后产品的特性等均有重要影响.通过对揉碎后玉米秸秆进行压缩试验,研究了在不同初始密度下以不同速度压缩时,不同含水率揉碎玉米秸秆不同个体形状的可压缩性,并分析了不同压缩条件下揉碎玉米秸秆体积模量与压缩量、压缩密度之间的关系,获得了体积模量与压缩密度关系的数学模型.研究结果表明:揉碎玉米秸秆的可压缩性受到喂入揉碎玉米秸秆含水率、初始密度和压缩速度的影响,且当压缩密度大于230 kg/m3时,随压缩密度的增加,可压缩性明显降低.     

A method for assessing the impact of load on mechanical stability and on physical properties of soils

Methods to quantify the mechanical strength of agricultural soils in order to assess the trafficability are presented. The pedotransfer functions relating the precompression stress as a measure of soil strength and the depending soil parameters are also shown. By using cohesion and angle of internal friction values, the precompression stress can be calculated using the multiple regression equations. Horizon specific values on the mechanical stability of arable soils is determined at various moisture suctions. Changes in dependence of gravel contents are also given. The stress transmission for specific soil horizons is calculated by using classified values of the concentration factor. The mechanical stability for the soil profile is then determined by comparing the actual pressures in a specific soil horizon with the corresponding value of the precompression stress. Stress dependent changes of soil physical properties only occur when applied stress exceeds the precompression stress. These changes in soil physical properties are dependent on soil suction, texture, structure and applied stress. Regression equations presented in this paper can be used to calculate the changes in soil physical and mechanical properties due to loading. The proposed method is a useful tool towards fulfilling the soil protection law in the Federal Republic of Germany.     

柔性电热板加热摞式热压工艺的研究与实践

在单层大开档压机中，将数块特殊制作的柔性电加热板按一定方式直接置于成摞堆放的板坯中对板坯进行加热加压。板坯为多层胶合板或细木工板。几年的研究与实践证明：与目前通常的刚性压板热压相比，板坯压缩率较小（低于４％），能源消耗也较低，电耗为３０～５０ｋＷｈ／ｍ３。在单板含水率为１４％～１８％的条件下，仍然有十分可靠的胶合，胶合强度均大于１．２ＭＰａ。     

夯实水泥黄土压缩性试验研究

为了探索夯实水泥土桩在黄土地区的适宜性及可靠性,通过压缩试验分析了不同影响因素对夯实水泥黄土压缩性的影响。研究表明:夯实水泥黄土的压缩性较原状黄土大大降低;夯实水泥黄土的压缩系数随着初始含水量的增大先降低后增大,在最优含水量附近达到最小值;压缩系数随着掺入比和夯实功的增大均呈减小的趋势。     

辊压处理大青杨板材的形体变化规律

常温下，以压缩率10％、20％、30％、40％和50％5个条件对饱水状态的大青杨(P．ussuriensis Kom)板材分别进行无约束径向和弦向辊压处理；研究辊压处理前后在全干、气干(含水率12％)和饱水3种测试状态下，试材在厚度、宽度和体积3个方面的尺寸形体变异及单位尺寸和体积变化的百分率。相对于压缩前，总体变化规律为：辊压所致瞬时变形在其后绝大部分可恢复，辊压后试材厚度方向尺寸变小(-0．154％～-4．500％)、宽度方向尺寸略变大(0～3．740％)、体积略为降低(-0．329％～-3．019％)。     

Interpretation of uniaxial,confined compression test data for agricultural topsoils

Traditionally, soil strength is estimated from uniaxial, confined compression tests by procedures adopted from classical soil mechanics. The heterogeneity of agricultural topsoil calls for an alternative approach. Undisturbed soil cores were collected in the plough layer of 14 soils in arable agriculture. Soil texture ranged from coarse sandy to silty loam soils with a maximum of 20% clay. The samples were drained to either of six matric potentials in the range from − 30 to − 300 hPa. Uniaxial, confined compression was applied to ∼800 kPa with strain-controlled stress application (1 mm min⁻¹). Measured strain was fitted to stress by the Morgan-Mercer-Flodin (MMF) model. The model fitted data remarkably well for all samples. Three fitting parameters of the model reflected physical characteristics of soil reaction to stress. The estimates of soil compressibility calculated from the model at 10 kPa (C₁₀) correlated closely and linearly to the C_s index considered to reflect elastic deformation in classical studies of soil compression tests. Soil bulk density and content of soil organic matter decreased C₁₀ as well as compressibility at 100 (C₁₀₀) and 400 kPa (C₄₀₀). A complex pattern in the effects of soil texture and soil moisture on compressibility was revealed. The pattern in strain-stress data is interpreted as a reflection of a gradual transition from elastic to plastic deformation of the mixture of structural units. The MMF model is suggested for interpretation of strain-stress data from uniaxial, confined compression tests. This implies use of stress in a linear scale.