Comprehensive tests on rising height of capillary water for coarse grained soil

According to the comprehensive tests on the rising height of capillary water for seven kinds of different coarse grained soil by use of the method of standpipe,the relationship between the rising height of capillary water and time was obtained,and the influencing factors and rules were analyzed.The data of the steady rising height of capillary water were obtained,and the regression equation of coarse grained soil on steady height and physical indexes(effective grain d 10 and porosity n) was found.Compared with Hazen's and other expressions that could estimate the steady height of capillary water of coarse grained soil,the proposed method is satisfactory and the defects of the latter were pointed out.

Stochastic seismic response of multi-layered soil with random layer heights

This paper deals with the effect of layer height randomness on the seismic response of a layered soil. These parameters are assumed to be lognormal random variables. The analysis is carried out via Monte Carlo simulations coupled with the stiffness matrix method. A parametric study is conducted to derive the stochastic behavior of the peak ground acceleration and its response spectrum,the transfer function and the amplification factors. The input soil characteristics correspond to a site in Mexico City and the input seismic accelerations correspond to the Loma Prieta earthquake. It is found that the layer height heterogeneity causes a widening of the frequency content and a slight increase in the fundamental frequency of the soil profile,indicating that the resonance phenomenon is a concern for a large number of structures. Variation of the layer height randomness acts as a variation of the incident angle,i.e.,a decrease of the amplitude and a shift of the resonant frequencies.

Seismic responses of the steel-strip reinforced soil retaining wall with full-height rigid facing from shaking table test

To investigate the seismic response of the steel-strip reinforced soil retaining wall with fullheight rigid facing in terms of the acceleration in the backfill, dynamic earth pressure in the backfill, the displacements on the facing and the dynamic reinforcement strain distribution under different peak acceleration, a large 1-g shaking table test was performed on a reduced-scale reinforced-earth retaining wall model. It was observed that the acceleration response in non-strip region is greater than that in potential fracture region which is similar with the stability region under small earthquake,while the acceleration response in potential fracture region is greater than that in stability region in middle-upper of the wall under moderately strong earthquakes. The potential failure model of the rigid wall is rotating around the wall toe. It also was discovered that the Fourier spectra produced by the inputting white noises after seismic wave presents double peaks, rather than original single peak, and the frequency of the second peak trends to increase with increasing the PGA(peak ground amplitude) of the excitation which is greater than 0.4 g. Additionally,the non-liner distribution of strip strain along the strips was observed, and the distribution trend was not constant in different row. Soil pressure peak value in stability region is larger than that in potential fracture region. The wall was effective under 0.1 g-0.3 g seismic wave according to the analyses of the facing displacement and relative density. Also, it was discovered that the potential failure surface is corresponds to that in design code, but the area is larger. The results from the study can provide guidance for a more rational design of reinforced earth retaining walls with full-height rigid facing in the earthquake zone.

磷矿粉在石灰性土壤中对紫花苜蓿的施用效果

磷矿粉是一种难溶性磷肥,一般认为其在石灰性土壤上施用效果不好。苜蓿(Medicago sativa)利用难溶性磷的能力较强,为探索磷矿粉在石灰性土壤对苜蓿的施用效果,本研究以3种不同品位磷矿粉PRⅠ、PRⅡ、PRⅢ为磷肥源,以水溶性磷肥过磷酸钙为对照(CK),对3个紫花苜蓿品种‘阿尔冈金’(M1)、‘陇东苜蓿’(M2)、‘金皇后’(M3)进行土培盆栽试验,研究了不同磷矿粉处理下紫花苜蓿两茬的生长、营养品质、磷素的吸收利用以及土壤磷素含量。结果表明,第2茬收获时PRⅠ处理下M1和M3的株高明显高于CK,PRⅢ处理下M2的株高明显高于CK。M1两茬干重均表现出PRⅠ磷矿粉处理最高,两茬总生物量干重达到8.61 g,比CK高46.9%,3个磷矿粉处理下M2第1茬、第2茬和总生物量干重均高于CK,磷矿粉处理对M3的生物量没有明显作用。PRⅠ和PRⅢ处理显著提高了第2茬M1的粗蛋白含量,PRⅢ处理M1和M2紫花苜蓿的粗脂肪含量均高于CK。第1茬磷矿粉处理中PRⅡM3处理的钙含量达到最高值,为2.18%,与CKM3处理差异不显著(P>0.05),第2茬PRⅠM1和PRⅢM2处理的钙含量最高,均为1.56%。PRⅠ和PRⅢ处理可显著提高第2茬M1和M2的磷吸收效率,PRⅠ能显著提高第1茬M1和M2的磷利用效率,而PRⅡ均显著提高了3个紫花苜蓿品种第2茬的磷利用效率。除PRⅡM1处理外,磷矿粉处理均显著提高了土壤全磷含量,且3个品种均表现出在PRⅠ和PRⅢ处理下的土壤全磷含量高于PRⅡ,相比施肥前,磷矿粉处理均显著提高了土壤有效磷含量,M3的土壤的有效磷含量低于M1和M2。因此,磷矿粉在石灰性土壤对紫花苜蓿的生长、营养品质和磷素吸收利用可超过或达到与过磷酸钙相当的水平,其效果因磷矿粉品位和苜蓿品种不同而有差异,本研究条件下,PRⅠ磷矿粉,M1和M2品种表现出较好的施用效果。

冲击荷载下含夹层饱和砂土孔压变化规律分析

砂土中夹层的性状会影响饱和砂土孔压发展,从而影响砂土层变形。为研究夹层位置、厚度和种类等不同夹层状态下砂土液化过程中的孔压变化规律,设计了冲击荷载作用下层状砂液化试验,建立了含夹层饱和砂土理论模型,并将试验结果与理论分析进行对比。结果表明:含夹层饱和砂土的孔压发展呈现3个阶段,即快速上升、快速消散、缓慢消散阶段。高渗透性夹层高度越高,其下方土层孔压快速消散时长越短,越快趋于稳定值,但消散总时长无明显影响;低渗透性夹层高度或厚度的增大,均会使夹层上方孔压快速消散阶段速率加快,孔压消散稳定阶段延长,孔压消散总时长随之线性增长;同时,孔隙水会在低渗透性夹层下方形成水膜,夹层高度或厚度的增加均会使水膜持续时间增长,但水膜形态主要受夹层厚度影响。试验结果与理论分析较为一致,说明了试验的可靠性。

马铃薯跳跃高度与分离时间试验研究

针对现有马铃薯收获机摆动筛式薯土分离筛装置破皮率和分离输送效率两者难以平衡的问题,对马铃薯输送分离作业进行了室内试验,确定了影响马铃薯破皮率和分离输送效率的主要作业参数。以马铃薯在摆动分离筛上的最大跳跃高度和分离时间为指标进行室内单因素试验和正交试验。单因素试验表明:马铃薯在摆动分离筛上最大跳跃高度与马铃薯质量、曲柄转速呈正相关,与筛杆间距、筛面倾角呈负相关;分离时间与筛杆间距呈正相关,与马铃薯质量、曲柄转速、筛面倾角呈负相关;筛杆材料65Mn-橡胶表现较好。正交试验表明:影响马铃薯最大跳跃高度的主次顺序为筛杆材料>筛杆间距>筛面倾角>曲柄转速;影响马铃薯分离时间的主次顺序为筛面倾角>筛杆间距>曲柄转速>筛杆材料;较优的分离筛参数组合为曲柄转速200r/min、筛面倾角21.7°、筛杆材料65Mn-橡胶、筛杆间距50mm。得到的试验数据和结论可为马铃薯输送分离装置的结构改进和参数优化提供参考。

南通路基土毛细水上升高度试验探究

毛细水上升会产生路基病害,以南通某干线公路路基土为研究对象,进行毛细水上升高度直接观测法试验,探究干密度、颗粒分布、含水率对毛细水上升高度的影响。结果表明:不同含水率的土样,随着干密度的增大,毛细水上升高度均呈减小趋势;随着颗粒分形维数的增大,毛细水上升高度均呈增大趋势;水泥改良含水率10%的土样,随着水泥掺量的增加和养护龄期的增长,水泥固化对毛细水上升的抑制作用明显;固化改良施工可选择8%水泥掺量、7天养护龄期或6%水泥掺量、14天养护龄期。

不平衡高差场地条件下软土基坑对撑支护设计分析

为了研究不平衡高差场地下软土基坑对撑支护方案,以珠海地区典型软土基坑为研究背景,利用Midas GTSNX有限元数值分析软件,针对3种支护方案进行数值模拟分析,得出了适合不平衡高差场的支护设计要点。研究表明:高差较大的软土基坑两侧土压力不平衡,对撑支护条件下深侧基坑向坑内位移较大,并可以引起浅侧基坑向坑外位移;坑内加固+桩外主动土加固的支护形式对基坑变形有明显抑制作用,若配合浅侧先挖的施工措施,对进一步控制基坑变形更有利;采用有限元数值分析软件进行不同支护方案的决策选型具有可行性。

大荷载矿石堆场中深厚吹填软土的地基处理及后评价

吹填淤泥形成陆域是资源利用和环境保护方面的优质解决方案,但当前吹填软土形成陆域的工程中,多数为荷载较小的堆场、工业园区道路、绿化区等。以青岛港董家口港区矿石码头工程20万吨级散货泊位后方预留堆场区的地基处理工程为例,对该工程的设计、施工及使用后6年的情况进行详细阐述,从多个角度展示深厚吹填软土的演变情况,详细介绍土体含水量、孔隙比、抗剪强度等指标在不同时期的变化,对比施工期沉降计算和监测数据,分析不同时期抗剪强度指标下矿石堆存的高度。结果表明,在大荷载矿石堆场中采用吹填软土形成陆域是可行的,通过合理的地基处理方式和有序增加堆存荷载,最终可使矿石堆场达到满载堆存。

复混肥配施土壤调理剂对龙椒农艺性状与土壤养分的影响

【目的】为提高土壤养分的供应平衡,使辣椒提质增产,研究了不同种类土壤调理剂与有机无机复混肥配施的最佳效果。【方法】通过盆栽实验,以辣椒秋美龙1号为试材,各设5组处理,分别为处理CK(不施肥)、T1(15-15-15复合肥)、T2(钙镁磷型土壤调理剂+有机无机复混肥)、T3(聚谷氨酸型土壤调理剂+有机无机复混肥)、T4(微生物菌剂型+有机无机复混肥),研究了土壤调理剂、配方、施肥量,对龙椒农艺性状及土壤养分指标的影响。【结果】T3处理在株高、茎粗、SPAD值等方面表现最好,单果重达12.13 g;其次是T4处理,单果重达9.3 g,但单株结果数达33个,表现又优于T3处理;农艺性状特性优劣综合排列为:T3>T4>T2>T1>CK。有机无机复混肥配施不同类型土壤调理剂均可提高土壤pH值、降低土壤容重、增加速效性养分含量、促进龙椒生长。【结论】综合考虑土壤肥力与龙椒需肥特性基础,折算施肥亩用量后得出,“聚谷氨酸型土壤调理剂60 kg+有机无机复混肥40 kg”的效果最佳。

Chemical Attributes of a Typic Acrudox Soil on Marandu Palisade Grass under Rotational Stocking, Liming and Nitrogen Fertilisation

Urochloa brizantha (synonymous of Brachiaria) is the most spread species of grass in the tropical world, primarily in regions with acid and low fertility soils. This study was conducted to investigate changes in the soil chemical properties of a Typical Acrudox submitted to a strategy of grazing with rotational stocking, liming and nitrogen fertilisation. Treatments involved combinations of two pre-grazing heights (25 and 35 cm) with two rates of nitrogen (50 and 200 kg·ha-1·year-1). All combinations received lime, P and K fertilization and an untreated control group was allocated according to a complete randomised block design, five replications. Soil sampling was done in layers of 0-5, 5-10, 10-20, 20-30 and 30-40 cm deep in pastures of U. brizantha Marandu (Palisade grass). The samples were analysed for pH, H+ + Al3+, soil organic matter (SOM), P, K+, Ca2+, Mg2+, exchangeable and calculated CEC, BS% and aluminium saturation. Liming and fertilisation improve the soil fertility. The highest organic matter contents were obtained for the 0-5 cm layer, with a nitrogen fertilisation of 200 kg·N·ha-1. The management practice for the pre-grazing height of 25 cm, regardless of the nitrogen, is the best strategy for soil quality and livestock production.

A site dependent top height growth model for hybrid aspen

In this study height growth models for hybrid aspen were developed using three growth equations. The mean age of the hybrid aspen was 21 years （range 15-51 years） with a mean stand density of 946 stems ha-~ （87-2374） and a mean diameter at breast height （over bark） of 19.6 cm （8.5-40.8 cm）. Site index was also examined in relation to soil type. Multiple samples were collected for three types of soil： light clay, medium clay and till. Site index curves were constructed using the col- lected data and compared with published reports. A number of dynamic equations were assessed for modeling top-height growth from total age.

Effect of Mulching and/or Watering on Soil Moisture for Growth and Survival of the Transplanted Tree Seedlings in Dry Period

Dry mulch, as soil moisture conservation techniques, is seldom practiced for growth and survival of transplanted tree seedlings in dry period in Eritrea. Field experiment was conducted at Halhale, Eritrea with Dry Hyparrhenia rufa, as a mulch, on a flat basin for growth and survival of seedlings of Grevillea robusta and Acacia polyacantha subspecies Campylacantha by involving four management practices: 1) mulching and watering basins (MW);2) no-mulching but watering basins (NMW);3) mulching but no-watering basins (MNW);4) no-mulching and no-watering basins (NMNW). The experimental design was CRD with three replications. MW and NMW were watered 180 litters (20 litters/month) but MNW and NMNW were not watered at all. Parameters such as soil moisture content of the basin, early growth performance of seedling and survival rate of the seedlings were studied. The result indicated that there were statistically significant differences (p < 0.05) among the treatment for soil moisture content and early growth performance of the seedlings. The average volumetric water content (VWC%) on 0 - 20 cm soil depth at the end of dry period of MW, NMW, MNW, and NMNW were 10.08%, 7.7%, 6.3% and 3.9% respectively. Mean height increment of seedlings of G. robusta of MW (100 cm), NMW (83.3 cm), MNW (31.5 cm) and NMNW (9 cm) were recorded, while the mean height increments of seedlings of A. polyacantha subsp. Campylacantha of MW (48 cm), NMW (25 cm), MNW (4.5 cm) and NMNW (3 cm) were recorded. The mean survival rate of G. robusta was 91.8% of which the highest (100%) survival rate was recorded under MW, NMW and MNW, but the lowest (66.7%) was recorded by NMNW. All seedlings of A. polyacanth subsp. Campylacantha were survived, irrespective of the treatments. The study concluded that soil moisture content, early growth performance of seedlings, and survival rate of transplanted tree seedling was improved by application of mulch.

黏土地基上海洋平台桩靴峰值阻力上限分析

在自升式平台的预压载过程中,桩靴在层状地基上较易发生“穿刺”现象,很大程度上影响着平台的安全运行。准确地分析桩靴峰值阻力,避免平台桩靴发生“穿刺”是非常重要的。采用极限分析上限定理,合理构建运动许可速度场,从理论上推导了层状地基上桩靴峰值阻力的上限解答。为了进一步验证峰值阻力理论解答的准确性,采用ABAQUS有限元软件构建了“桩靴—弹塑性海床”的三维数值模型,对桩靴贯入海床的过程进行了数值模拟,分析桩靴周围土体的塑性变形演变规律,研究土体的破坏机理。研究结果表明:推导的桩靴峰值阻力上限解答,能够较好地计算层状地基极限承载能力,通过与离心机试验和数值结果对比,计算误差在18%以内;给出的运动许可速度场能够较好地反映桩靴周围土体破坏模式;桩靴阻力达到峰值时,下层软土中的土塞高度约为桩靴直径的0.2倍。

软土地区铁路桥梁桥下堆载安全敏感性分析

针对软土地区铁路桥梁桥下堆载导致桥墩侧偏问题,以深茂铁路江茂段某32 m简支铁路桥梁为背景,采用非线性有限元软件MIDAS GTS建立桥下堆载力学模型,采用控制变量法,选取桩基类型、墩身高度、软土厚度、堆载高度等因素对铁路桥墩墩顶侧向水平位移的影响进行安全敏感性分析。结果表明:在相同边界条件下,摩擦桩对应的墩顶侧向水平位移小于柱桩;铁路桥梁墩顶侧向水平位移受墩高的影响较小;铁路桥梁墩顶侧向水平位移与软土层厚度呈强相关性,软土厚度越大,墩顶侧向水平位移越大;铁路桥墩墩顶侧向水平位移受堆载高度影响显著,根据变形限值反算出的堆载安全距离,与堆载高度呈二次函数关系。当在软土地区遇到同类桥墩侧偏情况时,可根据得出的相关结论初步判定导致铁路桥梁变形的主要敏感因子,以及堆载与铁路桥墩间的安全距离。

尺度效应对多光谱遥感监测土壤水分影响研究

尺度效应是指在无人机遥感观测中,随着遥感分辨率的变化,各尺度遥感反演得到的数据表现不一致的现象,影响多光谱遥感监测土壤水分的精度。为探究尺度效应对于无人机遥感监测土壤水分的影响,以冬小麦为研究对象,通过无人机搭载多光谱相机分别在19、37、55、74、92 m的不同高度(对应分辨率为10、20、30、40、50 mm)拍摄多光谱图像,并同时采集土壤含水率数据。使用ENVI5.3(64 bit)对多光谱图像进行掩膜处理,包括无掩膜处理(no mask,NM)、去土壤掩膜处理(Soil background removal by masking,SRM)、去土壤去阴影掩膜处理(Soil and shadow background removal by masking,SSRM),获取各个高度下冬小麦的纹理特征。使用灰色关联法(Grey Relational Analysis,GCA)优选数据后,采用多元线性回归(Multiple Linear Regression,MLR)、BP神经网络(Back PropagationNeural Network,BPNN)和随机森林(Random Forest,RF)3种方法反演土壤含水率,使用R2和RMSE评价反演效果。研究结果表明:在采取的各种掩膜处理中,无掩膜方法反演效果最好。在各掩膜处理方法下表现最好反演模型是BPNN模型,在大部分情况下表现稳定有较好的反演效果,证明机器学习在遥感监测领域应用的可行性。冬小麦土壤含水率30 mm-NM-RF模型为最佳反演模型。在分辨率为40 mm,即无人机飞行高度74 m时,不同模型综合反演效果最佳,研究成果可应用于今后无人机监测土壤水分确定飞行高度。

基于Lagrange插值法提高击实试验精度的方法研究

文中针对土方击实试验,介绍了试验方法的选用和压实度的确定方法,分析了可能影响试验结果的因素,提出了击实试验余土高度控制在6 mm范围的“边击边算边测”控制方法。试验结果表明,“边击边算边测”的Lagrange插值法结合牛顿迭代法可求解较为精确的最大干密度和最优含水率,通过对比分析3点、5点、7点多项式的拟合结果,从准确性、精确性及试验数据处理的效率出发,建议采用三点二次多项式的Lagrange插值法。

移栽岷江柏生长生理特性及影响因素

为研究不同土壤含水率及日照对迁地保护后移栽岷江柏(Cupressus chengiana)生长生理状况的影响及影响因素,以岷江柏移栽苗为材料,并将岷江柏按初始株高(H)分级(H≤50 cm,50 cm<H≤100 cm,100 cm<H≤300 cm)进行移栽,同时采用控制单一环境变量的方法,分别设置日照时间(5、8 h)和土壤含水率(13.98%、12.67%、11.36%)等水热条件,培养18个月,研究各环境因素对岷江柏生长与生理指标的影响。结果表明:初始移栽株高显著影响18个月的移栽苗株高相对生长量和冠径相对生长量,短期内,适当延长日照时间和略微降低土壤水分,可促进岷江柏移栽苗的地径相对生长量。方差分析表明,对于土壤含水率在13.98%时,超氧化物歧化酶在5、6月份间存在显著差异;对于土壤含水率在12.67%、11.36%时,淀粉质量分数在5、6月份间存在显著差异。主成分分析表明,岷江柏移栽苗的生理指标对主成分贡献率较高(69.2%),抗氧化物质和渗透物质分别位于不同的主轴。

生物炭对加拿大杨苗圃土壤肥力及扦插苗生长的影响

在田间条件下,设置对照(B1)、化肥(B2)、化肥+8 t/hm^(2)生物炭(B3)、化肥+16 t/hm^(2)生物炭(B4)、化肥+24 t/hm^(2)生物炭(B5)5个处理,研究生物炭对加拿大杨苗圃土壤肥力和扦插苗生长的影响。结果表明,单纯施用化肥与对照相比显著提高了加拿大杨扦插苗的株高,添加生物炭可进一步提高加拿大杨扦插苗的株高。施用生物炭可提高土壤养分含量和酶活性,从而使土壤养分供应能力增强,有利于植物生长发育。不同生物炭施用量比较来看,加拿大杨苗圃土壤改良中生物炭施用量以16 t/hm^(2)为宜。

砒砂岩复配土对黄瓜生长特性的影响

以黄瓜(Cucumis sativus)为研究对象,研究不同比例的风沙土与砒砂岩复配土对其生长状况与产量的影响。将风沙土与砒砂岩按照1:0、1:1、1:3、1:5、0:1、3:1、5:1的比例复配后,取温室外试验区10 cm深度的栗钙土设置为对照土样(CK)。通过比较在不同配土比例下,黄瓜株高、冠幅、结实量等生长特性的差异,探究最适宜黄瓜生长的复配比例。结果表明:(1)在风沙土与砒砂岩复配比例为1:3时,黄瓜株高81.50 cm、东西冠幅30.50 cm、南北冠幅29.50 cm、果实总质量1475.80 g、单瓜重147.58 g,除东西冠幅外,其他各项指标均呈现最优状态。(2)随着幼苗的生长,生长特性逐步呈现为线性增加的趋势,其中1:3的增长速度在各时期都是最快的,7月22日—9月16日株高增长量为73.25 cm、东西冠幅增长量为22.50 cm、南北冠幅增长量为23.00 cm。综上,风沙土与砒砂岩1:3的复配比例有利于黄瓜的生长,更能促进结实。