水泥稳定三峡库区风化砂回弹模量试验及模型评估

以水泥稳定三峡库区风化砂的回弹模量值为研究对象,在风化砂中分别掺入3%、5%、7%、9%的水泥制作试样,然后各自养护7、14、21、28、35、56、70 d,开展室内回弹模量试验。试验结果表明:掺水泥能显著提高风化砂的回弹模量值。在相同的养护龄期下,随着水泥掺量的增加,回弹模量值逐渐增大,增长的幅度先大后小,二者呈现良好的对数函数关系;在相同的水泥掺量下,随着养护龄期的增长,回弹模量值也逐渐呈线性增大,且在最初养护的28 d内,回弹模量值的增长占整个测试期内的95%左右。通过回归分析,分别建立了水泥掺量与回弹模量值之间、养护龄期与回弹模量值之间的数学模型,再通过补充试验,进一步验证了所建数学模型的正确性及精确度。     

面向刚度曲线的汽车前保险杠缓冲块优化设计

以掺天然砂砾改良的红粘土为研究对象,采用室内承载板法测定回弹模量,通过不同初始干密度下的回弹模量试验,深入研究了天然砂砾改良红粘土的回弹模量随初始干密度的变化规律,建立了不同初始干密度下回弹模量的预估模型。试验结果表明:在同一天然砂砾掺量下,随着初始干密度的提高,红粘土的回弹模量逐渐增大。当初始干密度由低向最大干密度增大时,回弹模量增长速度较快,当初始干密度超过最大干密度继续增大时,回弹模量增长速度变缓;在同一初始干密度下,当天然砂砾掺量从0增至30%时,回弹模量的增长幅度较小,当天然砂砾掺量超过30%而继续增长时,回弹模量增长幅度较大;初始干密度由1.6 g·cm^-3增长至2.0 g·cm^-3时,回弹模量增长值随天然砂砾掺量的增加而逐渐增大。分别建立了回弹模量随初始干密度及天然砂砾掺量变化的预估模型,通过补充试验,验证了预估模型的准确性。     

Experimental Study on the Compressive Property of Luojiashan Clay

This paper carried out an experimental study on the compressive property of Luojiashan Clay at Wuhan University. In order to investigate the influence of compaction degree, compaction water content and saturation state of compacted soil on the compressive property of clayey fill, compression tests were done on the samples compacted to different water content around optimum moisture content by different degrees of compaction. The theory of compacted soil structure was used to explain mechanism of the influence, and it was the change of soil structure that caused the variation of compresSive property. The results of the tests show that it was at agiven range of stress that degree of compaction and compaction water content have influence on the compressive prop- erty of clayey fill. Around optimum moisture content with degree of compaction decreasing or compaction water content increasing, the compressive deformation of clayey fill increased. When compacted fill was saturated by water soaking, the compressive deformation increased much, and the clayey fill compacted at greater water con- tent than optimum moisture content showed smaller compressive deformation caused by saturation at other conditions the same.     

辽西北沙地流动沙丘土壤水分时空变化特征研究

以辽西北沙地流动沙丘为对象,研究了土壤水分运动的时空变化特征。结果表明：流动沙丘土壤含水率的时间变化与降雨有密切关系,春季土壤含水率较低,为0.1%~3.1%;夏季土壤含水率较高,为2.5%~5.1%;秋季土壤含水率略高于春季,为2.2%~3.6%。土壤含水率垂直变化位为：0~10cm土壤含水率变异程度较大,受降雨和蒸发影响强烈;10cm~80cm变异程度相对小些;80cm~120cm土壤含水率比较稳定。流动沙丘不同部位的土壤含水率受干沙层厚度频繁变化和降雨量影响显著,阴坡底含水率＞阳坡底＞阳坡中＞丘顶＞阴中。     

土壤水分调控对高产冬小麦生理特性及产量影响

采用田间防雨旱棚方法研究了高产小麦分蘖期、孕穗期、灌浆期的三个生育时期在不同水分胁迫下,冬小麦生理特性指标的变化、产量构成因素及最终产量的变化。结果表明：冬小麦各个生育时期对水分胁迫反应有显著差别,主要表现为光合速率、蒸腾速率、叶水势等方面;生育后期比生育前期对水分敏感性强,产量受后期水分影响较大;根据各时期光合速率、蒸腾速率、最终产量等指标得出高产冬小麦合理节水灌溉指标主要为各生育期田间持水量分蘖前期为45%~50%,分蘖后期到孕穗前期为55%~60%,孕穗后期至灌浆期要维持60%~65%左右。这种条件下可以获得较合理的生物产量和经济效益。     

异位发酵床垫料的直剪切及压缩试验研究

为研究不同含水率的条件下异位发酵床垫料:抗剪强度、黏聚力、内摩擦系数、压缩载荷的变化规律.本研究采用土壤力学试验方法,测定垫料五种不同含水率的相关参数.结果表明:当垫料含水率为29.22％～36.13％时,抗剪强度、内摩擦角系数会随着含水率的增大而增大;当含水率为45.55％～61.11％时,抗剪强度、内摩擦角系数会随...     

Influence on salinity and other constituents on the mechanical behaviour of clay soils

The irrigated soils of the El-Khemis valley (Algeria) are characterized by high clay and silt, and low organic matter contents, and often present high salinity levels. In order to better understand their mechanical behaviour, Proctor compaction tests were performed and consistency limits determined on a range of soils from the area. The statistical relationships between compaction characteristics, consistency limits, soil salinity and other soil constituents were examined. The liquid limit was positively related to the clay and fine silt contents whereas the plastic limit was positively correlated with fine sand and organic matter. Clay content and exchangeable sodium explained most of the variation of the plasticity index. The compaction tests showed that water contents at the compaction sensitivity threshold and at maximum compaction were both positively correlated with clay and organic matter contents. Overall, exchangeable sodium and electrical conductivity were only weakly correlated with the Atterberg limits and the compaction parameters. Irrigation of these soils with brackish water had therefore apparently little effect on their mechanical properties. However, their compactibility and wide plasticity in relation with their water retention properties suggest that they are susceptible to structural degradation.     

最大承载力状态下全风化花岗岩路基变形特性与控制方法

为了研究南方湿热条件下全风化花岗岩填筑路基的科学方法,以提高路基在运营期的耐久性与稳定性,对全风化花岗岩进行了湿法重型击实与加州承载比试验。结果表明：承载力最大状态下全风化花岗岩的含水率比最佳含水率更接近天然含水率。为进一步了解其湿胀特性,通过改变初始含水率进行了膨胀率试验,得到了全风化花岗岩在不同初始含水率下的干密度衰变规律;通过改进的固结试验对比分析了全风化花岗岩在最大承载力和最大干密度状态时的变形特性。结果显示：与常规的以最大干密度控制方法相比,全风化花岗岩在最大承载力状态下抗变形能力和稳定性更好。按最大承载力状态铺筑了全风化花岗岩路基试验段并进行了现场回弹模量和压实度检测,结果表明：最大承载力状态下全风化花岗岩路基完全能满足下路床94区的压实要求,为了满足路面对路基回弹模量的要求,基于变形等效原理提出刚度补偿设计方法,以确保全风化花岗岩路基整体刚度与耐久性。     

黑土机械压实对土壤结构和甜菜产量的影响

黑土机械压实是由于机械化作业引起的土壤结构破坏,导致土壤质量下降。通过对土壤孔隙比、土壤孔隙度比、土壤透气性、渗透率等指标的分析,明确了土壤压实积累区变化特征总体上表现为,随着机械压实次数的增加,土壤隙比和土壤孔隙度比均减小,通气性变差,土壤雨水入渗率降低,影响区域以5-10cm耕层土壤为最大,拐点在10cm处,对深层土壤的影响减小。土壤压实给甜菜生长造成不利影响,与对照比甜菜块根直径小6.67%-16.08%,甜菜块根长度短1.96%-17.65%,块根产量减产5.81%-24.13%,含糖率降低0.49-0.81度,糖产量降低4.73%-27.03%,碾压次数越多对甜菜产质量的降低作用越显著。     

木质素/皮胶/聚乙烯复合改良剂对风成沙稳定凋萎含水量影响

本研究旨在利用生物质基材料制备风成沙改良剂并研究其对风成沙稳定凋萎含水量的影响,确定改良剂改良效果最佳时各材料最佳掺量。笔者采用4水平3因素正交试验研究了木质素、皮胶、再生低密度聚乙烯对风成沙稳定凋萎含水量的影响。研究结果表明：3种材料制备的改良剂的加入对稳定凋萎含水量的提高具有显著地促进作用,其中皮胶影响达到极显著水平,木质素和聚乙烯影响不显著;皮胶掺量与土壤稳定凋萎含水量之间具有线性相关性,采用逐步分析法得二者间回归方程相关系数0.962。聚乙烯再生料在风成沙中掺量低于15%(wt%)时对风成沙土壤稳定凋萎含水量具有一定促进作用,超过15%时则会使该指标略有下降。木质素、皮胶、聚乙烯再生料在风成沙中添加比例为10%:20%:15%时,风成沙土壤稳定凋萎含水量达到最大值23.72%,改良剂改良效果最佳。该试验结果可为利用生物质材料改善风成沙保水性的研究提供一定的参考价值。     

DEM Analysis of Soil Arching of Pile Supported Embankment

Pile supported embankment has been widely used in road, airport and dam engineering due to effective construction and economic advantages which can effectively control the settlement and differential settlement. The soil aching effect is a key factor in the load transfer mechanism of pile supported embankment. Based on the current laboratory model test, a series of numerical simulations were conducted with the particle flow code PFC2D to study the contact force, principal stress, vertical and lateral displacements in embankment. The embankment fill and subsoil were simulated by the Disk,andthe pile and model box were simulated by the WallThe multi-layer compaction method was used to establish the Discrete Element Method models. The micromechanical properties of the embankment fill and subsoil were obtained from numerical biaxial compression test and simple compression test, respectively. The simulation results indicated that the soil arching in pile supported embankment was composed by multiple hemispherical arches with different centers, and the height of arching was about 5(s-a)/6. Within the soil aching height, the deflection of principal stresswas obvious, and the vertical and lateral displacements were significant.     

江淮丘陵区大蒜钾氮配施增产效应研究

通过多年田间试验,研究了江淮丘陵区大蒜钾氮配施的增产效应,结果表明：增施钾肥具有显著的增产效果,蒜苔增产28.7%~39.7%,蒜头相应产量提高19.5%~28.2%,平均增产率为36.4%和24.1%。钾肥的增产效率在两种氮肥水平下都较高,单位钾肥的增产量与土壤有效钾含量及施钾量呈极显著负相关;氮肥的增产效率除与土壤有效N含量有关外,还受施钾量和土壤有效钾含量的影响。应用逐步回归分析方法,建立了蒜苔和蒜头单位钾和N肥的增产数量与土壤有效钾、氮含量和施钾、施氮量的回归方程。     

土壤水分胁迫对水稻产量和品质的影响

以农大3号为试材,盆栽,控水,研究了不同生育阶段土壤水分（水势）胁迫（≤－75 kPa）对水稻产量和品质的影响。结果表明,孕穗中期土壤水分胁迫导致功能叶变短,穗粒数减少,生物产量与经济产量降低,糙米率、米粒长宽比、食味下降。分蘖期干旱胁迫使单穴有效穗数降低,生物产量与经济产量下降。出穗后干旱胁迫导致叶片萎蔫变黄,叶面积指数下降。乳熟期和灌浆期干旱胁迫,饱满粒率、饱满千粒重降低,整精米率下降。灌浆期干旱还导致垩白率、垩白度明显增高。蜡熟期干旱使叶绿素含量减少,胶稠度、蛋白质含量降低。     

深圳城市绿地土壤入渗性能及影响因素研究

研究深圳市城市绿地土壤水分入渗性能及其相关影响因素,以期为海绵城市建设,深圳市城市绿地水土保持提供参考。针对绿地不同植被类型（草地、乔木、灌木）及不同土层深度(0~30 cm、30~60 cm),利用Guelph入渗仪现场测定土壤饱和导水率,并分析土壤理化性质对土壤水分入渗的影响。结果表明：深圳绿地土壤入渗性能较差,饱和导水率不良及以下等级高达63.42%;乔木上层土壤及灌木上层土壤饱和导水率较高,均显著高于各自下层土壤饱和导水率(P<0.05);绿地土壤砂粒含量较高,平均达52%以上,土壤容重偏高,平均为1.62 g/cm ³。土壤质地可显著影响土壤入渗特性,砂粒含量越高,土壤渗透性越好(P<0.01),容重、含水率、砾石含量与土壤饱和导水率显著负相关(P<0.05)。深圳绿地土壤入渗性能较差,未来可考虑降低压实程度、提高土壤砂粒含量来改良土壤渗透性。     

Conversion Relationship of Indoor and Field Dynamic Modulus of Subgrade

The Falling Weight Deflectometer(FWD)test, Portable Falling Weight Deflectometer(PFWD)test and Dynamic Cone Penetrometer(DCP)test in field as well as indoor repeated loading test were carried out with three types of subgrade, clay, sandy and earth-rock mixture. The regression relationship of the parameters observed of these three different types of subgrade in field was investigated respectively. The indoor dynamic modulus changed along with different water contents and the relationship waspresented as well as the empirical relationship of the on-site and indoor dynamic The results indicate that in the three different subgrade conditions,a double logarithmic regression relationship between dynamic modulus(EP and EF)and average penetration rate(DP)and a parabola regression relationship between indoor dynamic modulus and water content exist. The regression relationship between field index and indoor dynamic modulus was significant as well.     

不同干扰对城市绿化用地土壤物理性质的影响

为了解压实对城市新建绿地土壤物理性质的影响,以西安植物园新园区为研究对象,依据土壤压实程度的不同以及地表植被的差异进行区域划分,对不同区域内的土壤分层采样,并进行土壤容重、孔隙状况、水分常数等物理性质的测定。结果表明：随着压实程度的增加,土壤各层次间的发生规律发生了改变,土壤出现退化现象。研究区域内的土壤容重偏高,平均值为1.52 g/cm³;土壤总孔隙度、通气孔隙度、土壤含水量、田间持水量、土壤饱和导水率明显偏低,平均值分别为44.71%、12.81%、15.46%、20.77%、20.7 mm/h。土壤容重与总孔隙度、通气孔隙度、田间持水量、自然含水量、饱和导水率之间呈极显著的负相关;通气孔隙度与饱和导水率、自然含水量、田间持水量之间均呈现显著的正相关。压实对各层土壤物理性质的影响表现为表层土>浅层土>深层土,人为践踏产生的压实只影响到表层土壤。     

水分胁迫对冬小麦抗性物质可溶性糖与脯氨酸的影响

利用盆栽方法,通过人工调控土壤含水率,设置轻度T1（相对含水率65%~70%）、中度T2（相对含水率55%~60%）和重度T3（相对含水率45%~50%）三个水分胁迫水平,研究不同生育期水分胁迫对冬小麦脯氨酸和可溶性糖含量的变化。通过测定与分析,认为冬小麦旗叶可溶性糖和脯氨酸含量的变化与水分胁迫密切相关,是保障冬小麦在干旱条件下正常生长的抗性物质。轻度水分胁迫对可溶性糖的影响主要集中在生长前期,中度和重度水分胁迫全生育期可显著提高可溶性糖含量,特别是乳熟期,中度和重度水分处理分别比CK增加78.6%和144.0%,因此可溶性糖可能是对种子成熟有特别作用的抗性物质。水分胁迫加强游离脯氨酸含量显著增加,说明脯氨酸也是重要的抵抗干旱的活性物质。在冬小麦全生育期中,开花期脯氨酸含量比正常含量高1倍左右,说明脯氨酸可能是保障正常开花的活性物质。     

温室黄瓜产量和土壤微生物随土壤水分的变化特征

在日光温室盆栽条件下,研究了土壤含水量对黄瓜产量和土壤微生物数量的影响,结果表明：(1)初花期,土壤水分为田间持水量80%~90%的处理土壤细菌数量最多,土壤水分为田间持水量70%~80%的处理和90%~100%的处理土壤细菌数量少,且二者差异不大,黄瓜初瓜期和盛瓜期当从土壤水分低变高时细菌数量增加,相反细菌数量减少,黄瓜生育后期当土壤水分从高变低时细菌数量增加,水分稳定不变或从高变为中等水平或从低变为中等水平时细菌数量减少。土壤真菌数量在土壤水分含量低时和土壤水分相对稳定的情况下增加,相反减少。土壤放线菌在黄瓜初花期和初瓜期各处理数量差异不大,盛瓜期各处理土壤放线菌的数量增加,生育后期多数处理土壤放线菌的数量有所下降。（2）初花期和初瓜期土壤水分为田间持水量的80%~90%、盛瓜期90%~100%、生育后期90%~100%的处理产量最高,为389.65g/株,比整个生育期低水、中水和高水的处理分别增产27.74%、18.21%、12.51%。     

温室黄瓜产量和土壤微生物随土壤水分的变化特征研究

在日光温室盆栽条件下,研究了土壤含水量对黄瓜产量和土壤微生物数量的影响,结果表明:(1)初花期,土壤水分为田间持水量80%~90%的处理土壤细菌数量最多,土壤水分为田间持水量70%~80%的处理和90%~100%的处理土壤细菌数量少,且二者差异不大,黄瓜初瓜期和盛瓜期当从土壤水分低变高时细菌数量增加,相反细菌数量减少,黄瓜生育后期当土壤水分从高变低时细菌数量增加,水分稳定不变或从高变为中等水平或从低变为中等水平时细菌数量减少。土壤真菌数量在土壤水分含量低时和土壤水分相对稳定的情况下增加,相反减少。土壤放线菌在黄瓜初花期和初瓜期各处理数量差异不大,盛瓜期各处理土壤放线菌的数量增加,生育后期多数处理土壤放线菌的数量有所下降。(2)初花期和初瓜期土壤水分为田间持水量的80%~90%、盛瓜期90%~100%、生育后期90%~100%的处理产量最高,为389.65g/株,比整个生育期低水、中水和高水的处理分别增产27.74%、18.21%、12.51%。     

Viscoelastic Model Analysis of In-situ Pressuremter Creep Test in Permafrost

In order to investigate the creep behavior of warm and ice-rich frozen soils, a number of pressuremeter tests were carried out in permafrost regions on the Qinghai-Tibetan Plateau with Menard pressuremeter. Then, the regression analysis results of the creep curves generated by Merchant model and relevant parameters were obtained. The test results indicate that the temperature plays a more important role than the water content in affecting the mechanical behavior of warm frozen soils. As pressure increases, the proportion of instantaneous strain in the total strain under each pressure decreases gradually. The regression results show that the instantaneous shear modulus increases linearly with decreasing temperature, but the delayed shear modulus as well as the viscous coefficient present a power function trend. Their peak values appear at the water content of 46%, which is rather different from the test result on lower temperature frozen soils.