置换减载与加筋复合处理方法对路基不均匀沉降控制效果研究     

卢谅  石通辉  杨东 《岩土力学》2019,(9):3474-3482

为了解决高速公路常见的不均匀沉降问题,提出了一种置换减载与加筋相结合的复合路堤处理技术。该技术利用具有一定刚度的PVC管置换路堤填土,减轻路堤自重荷载的同时发挥圆管的加筋作用,使得地基中附加应力减小,从而达到控制路基不均匀沉降的目的。为了验证该技术对地基不均匀沉降的控制效果,开展了置换减载与加筋复合处理路堤与未经处理普通路堤的大型模型试验,通过观测其在多级荷载作用下不均匀沉降的发展规律及沉降随时间的变化规律,并结合沉降理论进行分析验证,揭示了置换减载与加筋复合处理方法控制不均匀沉降的机制。该成果为加筋路堤或轻质置换路堤的设计及计算提供了理论依据。  相似文献   

Gas accumulation mechanism in Denglouku Formation of Changling fault depression,southern Songliao Basin,China     

YANG Guang  FAN Yeyu  LIU Changli 《世界地质(英文版)》2017,20(3)

The Changling gas field is occurs in tight sandstone reservoirs of the Lower Cretaceous Denglouku Formation in the Changling fault depression , southern Songliao Basin , China, which constitutes a new gas-pro-ducing area in the depression .Using information on the source-reservoir-cap rock assemblage of the Denglouku Formation, fault activity, and single well burial history of well CS 1, together with data on reservoir fluid inclu-sion and laser Raman spectroscopy , we described the formation of the Changling gas field and determine that this fault depression did not possess suitable conditions for hydrocarbon generation .Coal-derived methane gen-erated from underlying hydrocarbon source rock accumulated in the Lower Cretaceous Yingcheng Formation .At the end of the Late Cretaceous Qingshankou Stage , underwater volcanic eruptions occurred in the northern part of the Changling gas field near Qian'an, resulting in the reactivation of deep faults .Mantle-sourced inorganic CO2 migrated along faults to hydrocarbon gas reservoirs in volcanic rocks of the Yingcheng Formation ;Mean-while, displaced methane ( hydrocarbon gas ) migrated upward to sand reservoirs of the Denglouku Formation . The methane accumulated and formed secondary gas reservoirs ,Therefore fault activity was the main factor con-trolling the generation of gas reservoirs in the Denglouku Formation .The main accumulation period of the Yingcheng hydrocarbon gas reservoirs was 82 Ma.Whereas gas reservoir formation in the overlying Denglongku Formation was 79 Ma, slightly later than the time of formation of the Yingcheng gas reservoir in CS 1 well area. At 79 Ma, the burial depth of the Denglouku Formation was 1800-2000 m, the diagenesis is relatively weak and the physical properties of the reservoir are relatively favorable for accumulation .This period is not only at gas generation peak time of three sets of source rock but also at the reactivation of deep faults during the forma -tion of fault-bound depressions , thereby providing favorable conditions for the migration and accumulation of methane .  相似文献   

复合地基等效弹性参数研究   总被引：3，自引：0，他引：3  

张仪萍  王洋  李涛 《岩土力学》2011,32(7):2106-2110

考虑复合地基边界约束条件的影响,采用复合地基单元体模型,基于变形一致的原则,推导了复合地基在弹性变形阶段的等效变形模量和等效泊松比的解析解。研究表明,复合地基的等效弹性常数与复合单元体侧向约束条件有关,侧向约束越强,等效变形模量越大,泊松比越小。侧限条件和无侧限条件的等效弹性常数是复合地基各种约束情况下的2个极值,在较强的侧限约束条件下,等效泊松比随置换率的变化相对明显。研究还表明,按面积加权法计算的复合变形模量偏小,而计算的复合压缩模量偏大,等效压缩模量与加权法计算的差值随置换率不同而异,并随着桩土压缩模量比的增大而增加,其差异一般可达20%～30%  相似文献   

呼伦贝尔沙质草原表土物理力学性质     

殷玲  张德平  成永会  靳立宁  赵家明  巴日斯  海军  祁晓燕  屈建新 《中国沙漠》2015,35(4):930-936

通过野外现场调查、载荷试验、轻型圆锥动力触探及室内试验,对呼伦贝尔沙质草原厚度30 cm的表层沙土物理力学性质及承载力、剪切变形特征进行研究。结果表明:表层沙土工程分类为细砂,颗粒级配不良,沿深度有明显分层;干密度1.34～1.51 g·cm^-3,黏聚力12～27.4 kPa,内摩擦角22.5°～24.0°,变形模量8.5 MPa;各指标表明沙土的工程性质上部差于下部;沙土承载力特征值和极限承载力分别为150 kPa和300 kPa,承载力不足导致表层沙土发生冲剪破坏(塑性破坏)和整体剪切破坏(脆性破坏)。  相似文献   

岩溶石漠化区不同植被类型表土孢粉组合特征——以重庆市南川区南平镇石漠化区为例     

郝秀东  谢世友  欧阳绪红  罗伦德  石胜强  李林立  孙爱芝  赵增友 《中国岩溶》2010,29(3):301-311

通过对南平次生林地、杂草丛、坡耕地不同植被类型表土调查和采样,利用LuoPacias孢粉鉴定系统对所采的表土样品进行分析鉴定,以研究该区表土的孢粉组合特征。结果显示:（1）样品植物孢粉共由123种植物组成,其中以草本和蕨类植物占据优势,其孢粉含量为46.40%～76.47%,平均为65.55%,其次是乔木（主要为马尾松）,花粉含量为17.73%～46.84%,平均为26.40%,灌木植物花粉含量最小,为5.79%～12.50%,平均为8.26%,显示该区植被退化严重;（2）不同植被类型的表土孢粉组合差别明显, 次生马尾松林和次生樟树林的孢粉组合特征依次为马尾松—火棘—大楼梯草—里白和樟树—火棘—构棘—泽芹;杂草丛为裂叶荨麻—圆叶藜—车前子—里白;坡耕地为异叶花椒—裂叶荨麻—剑叶凤尾蕨—玉米,与其相应的实际植被情况大致相同,较好地反映出了石漠化地区现代植被的基本状况。   相似文献   

疲劳动剪应变门槛与武广高铁无碴轨道路堑基床长期动力稳定     

刘晓红  杨果林  方薇 《岩土力学》2010,31(Z2):119-124

针对武广高铁无碴轨道红黏土路堑基床长期动力稳定性问题,利用改造后的应力控制式动三轴仪代替国内尚无的剪应变控制式共振柱仪,测试土体疲劳动剪应变门槛值,提出了一套完整的试验方案和数据处理方法,为疲劳动剪应变门槛的确定开辟了新的试验途径。通过疲劳动三轴试验,获得了9种试验条件下红黏土疲劳动剪应变门槛值。按曲线走势特征,红黏土 - 曲线可分为稳定型、临界型、破坏型3类,且不同试验条件下同类型的曲线具有相似的走势特征;探讨了含水比、围压对红黏土疲劳动剪应变门槛的影响,给出了简单实用的疲劳动剪应变门槛经验估算公式;基于室内试验及现场动响应测试成果,采用动剪应变法初步评价了武广高铁无碴轨道红黏土路堑基床的动力稳定性,给出了不同物理状态下红黏土基床最小换填厚度建议值。研究成果为我国高速铁路无碴轨道土质路基动力稳定性评价及路堑基床换填厚度的确定提出了新的思路,也为红黏土疲劳特性的深入研究提供了宝贵的第一手资料。  相似文献   

三工河流域绿洲土壤有机碳的空间分布   总被引：1，自引：0，他引：1  

王玉刚  肖笃宁  李彦  郑新军 《中国沙漠》2011,31(1):101-107

为理解大尺度下土壤有机碳的空间分异特征,运用遥感与GIS技术,结合地统计学方法研究了三工河流域农业绿洲0~20 cm土层土壤有机碳的空间格局特征。结果表明:①流域尺度的土壤有机碳含量的理论变异函数符合球形模型,F检验达到极显著水平,在2~20 km的中尺度上具有中等强度的空间变异性和自相关性;②流域空间尺度上,土壤有机碳主要变化在4.5~6 g\5kg-1和10.5~12 g\5kg-1范围中,阜康绿洲区土壤有机碳含量明显要高于阜北绿洲区。土壤有机碳平均含量耕地最高,其次为草地,最低的为裸地。流域空间土壤有机碳储量为17.07×105 t,单位面积土壤有机碳储量:阜康绿洲>全流域>阜北绿洲。  相似文献   

The mechanism of cation and oxygen isotope exchange in alkali feldspars under hydrothermal conditions   总被引：3，自引：1，他引：2  

Dominik R. D. Niedermeier  Andrew Putnis  Thorsten Geisler  Ute Golla-Schindler  Christine V. Putnis 《Contributions to Mineralogy and Petrology》2009,157(1):65-76

The mechanism of re-equilibration of albite in a hydrothermal fluid has been investigated experimentally using natural albite crystals in an aqueous KCl solution enriched in ¹⁸O at 600°C and 2 kbars pressure. The reaction is pseudomorphic and produces a rim of K-feldspar with a sharp interface on a nanoscale which moves into the parent albite with increasing reaction time. Transmission electron microscopy (TEM) diffraction contrast and X-ray powder diffraction (XRD) show that the K-feldspar has a very high defect concentration and a disordered Al, Si distribution, compared to the parent albite. Raman spectroscopy shows a frequency shift of the Si-O-Si bending vibration from ~476 cm⁻¹ in K-feldspar formed in normal ¹⁶O aqueous solution to ~457 cm⁻¹ in the K-feldspar formed in ¹⁸O-enriched solution, reflecting a mass-related frequency shift due to a high enrichment of ¹⁸O in the K-feldspar silicate framework. Raman mapping of the spatial distribution of the frequency shift, and hence ¹⁸O content, compared with major element distribution maps, show a 1:1 correspondence between the reaction rim formed by the replacement of albite by K-feldspar, and the oxygen isotope re-equilibration. The textural and chemical characteristics as well as the kinetics of the replacement of albite by K-feldspar are consistent with an interface-coupled dissolution-reprecipitation mechanism.  相似文献   

福建三明地区被污染土壤的磁学性质及其环境意义   总被引：44，自引：8，他引：36       下载免费PDF全文

琚宜太  王少怀  张庆鹏  旺罗  邓成龙 《地球物理学报》2004,47(2):282-282

对福建三明某钢铁厂和火电厂附近的污染表土样品进行了多参数的岩石磁学测试分析,包括χ T曲线、磁滞回线、等温剩磁获得曲线等. 三明地区污染表土中的磁性矿物有磁铁矿、赤铁矿和磁黄铁矿. 样品中磁性矿物的平均粒度较粗,为较大的准单畴,甚至多畴,粒度明显大于成土作用所产生的磁性颗粒. 粗粒的磁铁矿颗粒是污染物的主要磁性组分. 虽然磁化率测量可以作为一种简单、快速而且廉价的检测污染土壤的方法,但同时辅以必要的岩石磁学测量将有利于提取更多的污染信息. 对于低磁化率的污染土壤,亚铁磁性硫化物的存在可以作为土壤可能被污染的证据之一.  相似文献   

The effect of conservation tillage on runoff erosivity and soil erodibility during concentrated flow     

A. Knapen  J. Poesen  G. Govers  S. De Baets 《水文研究》2008,22(10):1497-1508

Crop residues in conservation tillage systems are known to cause both a reduction in the erosive runoff power and an increase in the topsoil erosion resistance. In this study, the relative importance of both mechanisms in reducing soil loss by concentrated flow erosion is examined. Therefore, a method to calculate the effective flow shear stress responsible for soil detachment in the presence of a residue cover is applied. The determination of effective flow shear stress is based on the recalculation of the hydraulic radius for residue treatments. The method was tested in a laboratory flume by comparing soil detachment rates of identical pairs of soil samples that only differ in the presence or absence of crop residues. This shear stress partitioning approach and a soil detachment correction were then applied to a dataset of soil detachment measurements on undisturbed topsoil samples from a no‐till field plot on a loess‐derived soil, sampled during one growing season. Results indicate that only a small fraction (10% on average) of the difference in soil detachment rate between conventional and conservation tillage can be attributed to the dissipation of shear forces on the residues. The remaining decrease in soil detachment during concentrated runoff after a two‐year application of conservation tillage can be explained by the increased dry bulk density and root and crop residue content in the topsoil that reduces soil erodibility. After correcting for the presence of residues, the temporal variability in soil detachment rates (D_r) during concentrated flow for a given flow shear stress (τ) for both treatments can be predicted fairly well (R² = 0·87) from dry soil bulk density (DBD, representing consolidation effects), soil moisture content (SMC, representing antecedent rainfall conditions), the dry mass of organic material (OM, representing root growth and residue decomposition) and saturated soil shear strength σ_{s, sat} using an equation of the form: This study is the first to show that the effect of conservation tillage on soil detachment rates is a result of soil property modifications affecting soil erodibility, rather than a result of the surface residue decreasing flow erosivity. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献