聚乙烯微孔波纹管排水系统在播山沟水坠坝施工中的应用研究

水坠筑坝施工期坝体排水常采用沙井、沙沟等设施。在沙石料缺乏的甘肃省定西县播山沟水坠坝施工中，采用聚乙烯微孔波纹管网进行坝体排水，取得良好的效果。播山沟坝坝高２３．５ｍ，其中冲填坝高１６．５ｍ，间歇冲填施工，布设聚乙烯微孔波纹管网３层．纵横交叉贯通，管外缠绕塑料编织布滤水，铅丝绑扎接头，在停冲期埋设水平管网。实测施工期波纹管排水量３３２８．６７ｍ３，占计算应排水量的８３．３％；最大日排水量为３６．２８ｍ３，日排水量与冲填泥浆浓度及停冲后的天数密切相关。该坝施工期未发生坝坡鼓肚、滑坡等问题。     

高寒地区水坠坝冬季施工技术试验研究

水坠筑坝是我国创造的一种快速、经济筑坝方法,但高寒地区冰冻期长,冲填施工受到季节限制。为此,青海省水科所等单位进行了水坠坝冬季施工技术研究。本文论述了高寒区冬季水坠筑坝施工技术试验成果,并应用热平衡原理对冲填泥浆的冻融与脱水固结规律进行了研究分析。试验研究表明,高寒区冬季水坠筑坝,边埂修筑采取“控温快速压实法”可以达到干容重1.69/cm~3的设计要求;昼冲夜停采取“浮冰法”可避免坝内形成冰夹层;间歇冲填采取打孔捅透泥浆冰结层的办法,在气温变暖和坝内泥浆热量传递下,厚约2m的冻结层十个月内可全部消融。据对坝体干容重、含水量、孔压、位移、沉陷等观测,坝内泥浆脱水固结正常,坝体稳定。试验坝已投入蓄水运用。     

重粉质壤土泥浆泵筑坝人工管网排水技术研究

人工管网排水技术在泥浆泵筑坝工艺中的应用,为重粉质壤土区修筑泥浆坝提供了基础资料和理论指导,也为同类地区推广应用该筑坝技术,普及该排水措施提供了科学依据。以陕西省白水县西武村附近雷牙沟流域的黄土作为试验对象,对该排水系统的布设、施工方法及其排水效果进行了试验研究。结果表明,排水管道的材料选定和管道布设形式是影响坝体排水的决定性因素;聚乙烯微孔波纹管排水系统在一定程度上加速坝体脱水固结,但效果不显著;重粉质壤土黏粒含量较高,致使泥浆排水困难。人工管网排水技术在泥浆泵筑坝试验中的应用加速了坝体脱水固结,但是效果不佳,还需不断总结经验,选取理想的管道滤水材料,合理布设排水管道并完善排水设施。     

中粉质壤土泥浆排水固结规律研究

泥浆的排水固结变化对水坠坝筑坝过程中坝体排水系统的合理布设具有重要的指导作用。将中粉质壤土以1∶1,1.5∶1和2∶1的土水比制成泥浆,并将制得泥浆分别填充在高度为50,100,150和200cm的聚乙烯波纹管中,对其排水量、上析水量、下渗水量和固结沉陷量等指标进行测定。结果表明,同一土水比的泥浆,上述指标随着泥浆填充高度的增加而增大;同一泥浆填充高度,上述指标随着土水比的增大而减小。泥浆的排水量、固结沉陷量主要集中于前24h,排水量最大可占总排水量的89.48%,固结沉陷量最大可占总固结沉陷量的93.24%。因此,在实际筑坝过程中土水比较小时,应注重坝体泥浆的前期排水,并加强表层排水;土水比较大,充填高度较小时,可考虑不布设坝体泥浆表层排水措施,而要加强下渗水的排水措施。     

高黏土地区水坠坝立体网状排水技术研究

在高黏土地区水坠坝施工采用立体网状排水技术 ,土壤含黏土量可突破 15 %的限制 ;日均排水 6 5m3,比盲管、沙沟、沙井排水量大 3倍以上 ;提高坝体强度 ,工效比采用沙沟、沙井排水技术提高 1 8倍以上 ,降低造价 5 0 %以上 ;比碾压技术提高工效 11倍 ,工程总造价降低 2 0 %。     

水坠坝裂缝的简易灌浆法──自重压力灌浆法

水坠坝裂缝的简易灌浆法──自重压力灌浆法杨禄润（宁夏彭阳县水保站，７５６５００）利用重粉质壤上填筑的水坠坝，在施工期坝体内基本上是一个“流态区”，当边埂高出冲填泥面较多（０．８～１．２０ｍ）ｌｈｊ形成重力式埂时，上部边埂依附在冲填泥池上的重量增大，此...     

槐沟水力冲填坝滑坡分析及冲填体剪强度指标的探讨

粘粒含量较少的轻，中粉质壤土作冲填土料修建水坠坝，在黄土高原地区已被广泛应用。重粉质壤土作为冲填土料，由于其渗透系数小，脱水固结速度慢，施工期易形成滑坡。对于冲填泥浆，由于在实验室不易控制，且变形较大，其抗剪强度指标的实验室测定目前还是困难的。     

土工布排水设施在水坠坝施工中的应用及效果

<正> 土工布,又名土工织物,欧美称作“土上纤维(Geofabrie)”、渗滤布(Filfercloth)等。国外对它的研究。使用较早,我国80年代才在水利、冶金、国防等部门研究试用。1989年4月至12月,水利部海河水利委员会与太原市水保试验站共同进行了《水坠坝施工期土工布的脱水固结》的试验研究。试验表明,在水坠坝施工中采用土工布排水设施,具有排水效果好,施工进度快,省劳节资等优点。本文就水坠筑坝中应用土工布排水设施的效果进行分析。     

高寒地区水坠坝冬季施工技术试验研究(续)

<正> 四、边埂修筑与泥浆制造、输送 (一)边埂控温快速压实法。在水坠坝施工中,边埂的填筑碾压须与泥浆冲填同时进行。室内模拟试验表明,筑坝土料为负温时,在15击击实功能下,土温愈低,所能达到的干容重越小;而只有土温在0℃以上、含水量在塑限以下时,方可达到1.69/cm~3的设计干容重(详见表4、图8)。     

水坠坝建设中的水枪冲土及其筑坝效应

介绍了新一代冲土水枪的性能及其施工应用效果。在施工试验中系统观测了施工工效、施工成本、泥浆浓度以及高浓度泥浆的填筑效应。采用水枪冲土造泥能进一步节省工程费用,而且能造出浓度很高的泥浆,形成塑态。这种泥浆的连续上坝对水坠坝的安全稳定十分有利,同时还会产生3种效应:一是可以缩小边埂的宽度,二是可以加快冲填速度,三是可以提高重粉质壤土水坠坝的经济合理性。     

基于两种土质的暗管土工布外包料反滤效果对比试验

为了研究土质状况对暗管土工布外包料反滤效果的影响机制，该研究选取安徽蚌埠地区粉土、宁夏平罗地区砂粉土和4种热熔纺黏丝无纺布进行了室内土柱试验，对比测试了两种土壤在不同土工布防护措施下的流量、土壤和土工布渗透性变化过程，并对土工布的透水和防淤堵性能做出评价，同时从颗粒迁移的角度出发，对流量随时间变化出现先下降后上升再下降的现象(“驼峰”现象)进行了成因分析。结果表明，砂粉土土质与单位面积质量为68 g/m²的土工布、粉土土质与单位面积质量为90 g/m²的土工布之间的适配性较好，土工布能够通过颗粒筛选的方式将织物上方土壤特征粒径d₉₀值(小于该粒径值的土壤颗粒质量分数为90%)提升20%以上，诱导其表面高透水性土壤骨架的形成。“驼峰”现象是土壤颗粒迁移和土工布颗粒筛选二者共同作用下的结果，表征了土壤与土工布之间出现了良好的适配性。研究成果可为安徽蚌埠、宁夏平罗以及相似土质地区暗管排水土工布外包滤料的选择提供技术支持。     

Structure and hydraulic properties of the boreal clay soil under differently managed buffer zones

Vegetated buffer zones (BZs) between arable fields and bodies of water are commonly established to reduce erosion and run‐off of particle‐bound nutrients. Functioning of a BZ depends on soil structure, as it is important for water infiltration. Therefore, it is vital to understand how varying management practices affect soils of BZs. We studied the structural and hydraulic properties of three differently managed BZs established in a boreal Vertic Stagnic Cambisol (clay, 51%). The three management practices for vegetation were as follows: natural with no treatment, harvested yearly and grazed by cattle. We used bulk density and macroporosity, together with a pore geometry index (air permeability per unit air‐filled porosity), to describe the soil structural properties. Hydraulic properties were measured at different length scales by means of an aggregate sorptivity test, saturated hydraulic conductivity of the core samples and field‐saturated hydraulic conductivity. Vegetation management markedly affected the physical properties in the top 5 cm of the soil. Properties were least favourable for infiltration at the grazed site, with the greatest bulk density, least macroporosity and hydraulic conductivity or greatest pore tortuosity. In general, spatial variation in zones with restricted and good hydraulic conductivity together with reduced aggregate sorptivity in the deeper horizons made the soil prone to preferential flow when initially dry. Prolonged wetness, on the other hand, reduced saturated hydraulic conductivity significantly, resulting in surface run‐off. Harvesting was considered the best management practice due to its inherent capacity for reducing the soil nutrient content and because it has minor implications for soil physical properties.     

Effects of soil compaction and water‐filled pore space on soil microbial activity and N losses

Abstract

Soil compaction is a significant production problem for agriculture because of its negative impact on plant growth, which in many cases has been attributed to changes in soil N transformations. A laboratory experiment was conducted to study the effect of soil compaction and water‐filled pore space on soil microbial activity and N losses. A hydraulic soil compaction device was used to evenly compress a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudults) soil into 50 mm diameter by 127 mm long cores. A factorial arrangement of three bulk density levels (1.4, 1.6, and 1.8 Mg/m³) and four water‐filled pore space levels (60, 65, 70, 75%) was used. Fertilizer application of 168 kg N/ha was made as 1.0 atom % ¹⁵N as NH₄NO₃. Soil cores were incubated at 25°C for 21 d. Microbial activity decreased with both increasing water‐filled pore space and soil bulk density as measured by CO₂‐C entrapment. Nitrogen loss increased with increasing bulk density from 92.8 to 334.4 g N/m³ soil at 60% water‐filled pore space, for 1.4 and 1.8 Mg/m³, respectively. These data indicate that N loss and soil microbial activity depends not only on the pore space occupied by water, but also on structure and size of soil pores which are altered by compaction.     

Zur Bedeutung des Aggregierungsgrades für die Spannungsverteilung in strukturierten Böden

The effect of soil aggregation on stress distribution in structured soils The mechanical compressibility of arable soils can be described by preconsolidation load value and by the shear resistance parameters of the bulk soil and single aggregates. In order to quantify the effective stress equation must be also known the hydraulic properties of the soil in dependence of the intensity, kind, and number of loading events. The soil reacts as a rigid body at very fast wheeling speed inclusive a very pronounced stress attenuation in the top soil while stresses will be distributed in the soil threedimensionally to deeper depths at slower speed. These variations can be explained by the mechanical as well as by the hydraulic parameters of the bulk soil and single aggregates. Thus, the pore water pressure value of the bulk soil as a parameter of the effective stress equation further depends on the hydraulic properties of the inter- and intraaggregate pore system and continuity. As can be derived from the results the pore water pressure values are identical irrespective of the predessication for clayey polyhedres at high load while in coarse textured prisms the pore water pressure value depends on load and predryness. The consequences for soil strength under dynamic loading are shortly discussed.     

黄土沟壑高填方分层沉降监测与深层浸水试验

[目的]研究黄土沟壑地区高填方工程在填方完成后填筑体内部的变形状态,为后续相关研究提供基础依据。[方法]在某原始沟壑地形在进行高填方工程后,在填方场地内布设3组深层监测井,对填筑体内部土体的分层沉降、土压力以及体积含水率进行了持续12个月的监测。[结果]工后12个月时间里,沟壑高填方内部的主要变形量集中在填筑体与原始地基交接的位置,沟壑中心地下18—27m以及原始陡坡部位土层出现明显的张拉变形。在原始沟壑地形的影响下,填筑体内部表现出明显的土拱效应。地下18m以下不同部位土压力差异明显,中心部位土压力较小,不利于中央部位填土的自重压密。[结论]在黄土沟壑地形中进行高填方工程后,填筑体内部出现了对地下水上升表现敏感的区域,当地下水位上升时局部的湿化变形可能产生工程土洞、地面塌陷。