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1.
The purpose of this study was to assess the effect of long-term cultivation and water erosion on the soil organic carbon （OC） in particle-size fractions. The study site is located at Nihegou Watershed in the Southern Loess Plateau, China. The soil at this site is loess with loose and silty structure, and contains macropores. The results showed that the OC concentrations in sediments and in the particle-size fractions of sediments were higher than those in soils and in the particle-size fractions of soils. The OC concentration was highest in the clay particles and was lowest in the sand particles. Clay particles possessed higher OC enrichment ability than silt and sand particles. The proportions of OC in the silt fractions of soil and sediment were the highest （mean value of 53.87% and 58.48%, respectively）, and the total proportion of OC in the clay and silt fractions accounted for 96% and 98% of the total OC in the soil and sediment, respectively. The loss of OC was highest in silt particles, with an average value of 0.16 Mg ha^-1 y^-1, and was lowest in the sand （0.003 Mg ha^-1 y^-l）. This result suggests that the fine particle-size fraction in the removed sediment may be an important indicator to assess soil OC losses. 相似文献
2.
Amir Hossein Jafarzadeh-Haghighi Jusop Shamshuddin Jol Hamdan Norhazlin Zainuddin 《山地科学学报》2017,14(9):1763-1775
Limited information is available about factors of soil organic carbon(SOC) preservation in soils along a climo-biosequence. The objective of this study was to evaluate the role of soil texture and mineralogy on preservation of SOC in the topsoil and subsoil along a climo-biosequence in the Main Range of Peninsular Malaysia. Soil samples from the A and B-horizons of four representative soil profiles were subjected to particle-size fractionation and mineralogical analyses including X-ray diffraction and selective dissolution. The proportion of SOC in the 250-2000 μm fraction(SOC associated with coarse sand) decreased while the proportion of SOC in the 53 μm fraction(SOC associated with clay and silt)increased with depth. This reflected the importance of the fine mineral fractions of the soil matrix for SOC storage in the subsoil. Close relationships between the content of SOC in the 53 μm fraction and the content of poorly crystalline Fe oxides [oxalate-extractable Fe(Fe_o) – pyrophosphate-extractable Fe(Fe_p)] and poorly crystalline inorganic forms of Al [oxalateextractable Al(Al_o) – pyrophosphate-extractable Al(Al_p)] in the B-horizon indicated the importance of poorly crystalline Fe oxides and poorly crystalline aluminosilicates for the preservation of SOC in the Bhorizon. The increasing trend of Fe_o-Fe_p and Al_o-Al_p over elevation suggest that the importance of poorly crystalline Fe oxides and poorly crystalline aluminosilicates for the preservation of SOC in the Bhorizon increased with increasing elevation. This study demonstrates that regardless of differences in climate and vegetation along the studied climobiosequence, preservation of SOC in the subsoil depends on clay mineralogy. 相似文献
3.
《世界地质(英文版)》2015,(4)
The authors presented a new measuring method of the soil thermal conductivity,the probe method,which is designed and made based on the theory of line heat source. This method is used to measure thermal conductivity of coarse sand,fine sand and silty clay in different water contents. The results that measured by the probe method are well consistent with those of QTM-D_2. The soil thermal conductivity increases in different levels with the increase of the water content. Compared the soil thermal conductivity measured by the probe method in laboratory with in-situ experiment,it shows that the measuring gap gradually increases with the increase of the depth. The reason is that the in-situ measuring thermal conductivity can reflect the actual situation of the soil mass. 相似文献
4.
Landslides & debris flows formation from gravelly soil surface erosion and particle losses in Jiangjia Ravine 总被引：1，自引：1，他引：0
Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow. 相似文献
5.
为研究地埋管换热器在不同岩性地层的换热情况,在鲁西黄河冲洪积平原、山前冲洪积平原和低山丘陵区进行了以粉土、粉质粘土、细砂,粘土、粉质粘土、中粗砂,灰岩和花岗岩为研究对象的热响应试验,初步试验结果表明:每延米换热量(W/m)和平均热导率(W/m·k)花岗岩灰岩粉质粘土、中粗砂粉土、粉细砂。在岩溶地下水富水性强,径流速度快的地段灰岩平均热导率花岗岩。此项研究结果可为不同岩性地层浅层地温能开发利用工程地埋管换热器类型的选择,浅层地温能评价和开发利用提供基础数据。 相似文献
6.
《山地科学学报》2020,17(9):2179-2202
Residual soils are weathering products of rocks that are commonly found under unsaturated conditions. The properties of residual soils are a function of the degree of weathering. A series of index properties, engineering properties and geophysics survey examinations were performed on residual soils from two major geological formations in Iran. In the present research, the index properties of residual soils in the south of Mashhad city in Iran are investigated.Natural and artificial trenches were analyzed for evaluating the weathering profiles and collecting soil samples. Disturbed and undisturbed samples were obtained from each of the soil profile horizons resulting from weathering of different parent rocks.Subsequently, physical properties and mechanical properties of the soil samples were determined in accordance with ASTM standards. Also, the mineralogical composition, chemistry, and texture of the soil were evaluated in 51 profiles. The field observations showed the difference in the weathering profile of residual soils deposited on various rocks(igneous, sedimentary, and metamorphic). These profiles mainly consisted of two horizons includingresidual soil on top and saprolite at the bottom. The results of laboratory tests and geotechnical data showed that the properties of residual soil samples change by depth. Moreover, depending on the type of origin rock, the properties are different in various types of residual soils. In most of the samples, the moisture content of soil horizons was also increased by depth. Based on the unified soil classification(USCS), the soils of the upper horizons appeared to be classified as ML(Lean silt) and CL(Lean clay) while the soils of the lower horizons(saprolite zone) fall in SC(clayey sand), SM(silty sand), and SW(wellgraded sand) classes. Moreover, the results demonstrated that the particle size of the soil was increased by depth. Comparison of results of the geotechnical tests showed that properties of residual soils are changed by variations of depth, weathering level, and type of parent rock. Considering the concentration of the number of lines and the concentration of the points of intersection, the length and dimension fractal of lineaments in the southeastern part of the study area, it is evident that this zone possesses weathering severity and soil thickness. Fieldwork data from this zone have also verified the severity of weathering conditions. The analysis of lineaments trends in different parts of the study area indicated that the lineaments with the NW-SE trend have a strong effect on weathering development. The weathering depth depends on the orientation of bedding joints with respect to the slope in the study area. Slope inclination and soil thickness are controlled by weathering and erosion processes. 相似文献
7.
Corrosion behavior of steel in the juncture area of sea clay and sand was studied. The results show that galvanic corrosion occurred between steel samples buried in sea clay and sand, and that the polarity of the galvanic cell reversed after some testing later. The cause of reversing of polarity is discussed. 相似文献
8.
ＩＮＴＲＯＤＵＣＴＩＯＮＯｎｅｏｆｔｈｅｍｏｓｔｅｘｔｅｎｓｉｖｅｓｈｅｌｖｅｓｏｆｔｈｅｗｏｒｌｄｌｙｉｎｇｗｉｔｈｉｎｔｈｅｓｏｕｔｈｅｒｎｐａｒｔｏｆｔｈｅＳｏｕｔｈＣｈｉｎａＳｅａｉｓｔｈｅ1850000ｋｍ2ＳｕｎｄａＳｈｅｌｆｌｏｃａｔｅｄｂｅｔｗｅｅｎｔｈｅｔｈｒｅｅｌａｒｇｅｉｓｌａｎｄｓｏｆＳｕｍａｔｒａ,Ｂｏｒｎｅｏ,ＪａｖａａｎｄｍａｉｎｌａｎｄＡｓｉａ(ＬａＦｏｎｄ,1966).ＴｈｅｎｏｒｔｈｅｒｎｐａｒｔｏｆｔｈｅＳｕｎｄａＳｈｅｌｆｉｓｓｅｐａｒａｔｅｄｆｒｏｍｔｈｅＪａｖａＳｅａｓ… 相似文献
9.
Soils in the Knersvlakte are particularly prone to crusting and have lower inherent infiltrability than other soils across western southern Africa. Micromorphological techniques were used to examine the structure and porosity of soil crusts in the Knersvlakte to ascertain why crusting is so intense in this region. Quantile regression using boundary lines was employed to examine the relationships between infiltrability and soil properties for all samples （n = 67）. This analysis showed that infiltrability is potentially maximal at low water- dispersible ＇clay plus silt＇ content and low silt content （r^2 = 0.72 and 0.64; respectively, n = 67） （Figure 2）. The strength of crusts, pH, EC, clay mineralogy, and water-dispersible clay, silt and ＇clay plus silt＇ content were compared, and a pore analysis using optical microscopy was undertaken on images of six soil thin sections （n = 6） （circular and parallel polarizers）. Pore analysis was further undertaken on five horizontal slices of equal dimensions taken through each soil thin section. The porosity samples with low infiltrability （〈 100 mm·hr^-1, n = 4） had greater crust strength, lower porosity （both total and in the least porous slice） and greater water-dispersible ＇day plus silt＇ and silt content than the porosity samples with high infiltrability （〉 100mm·hr^-1, n = 2）. The porosity samples with low infiltrability showed a trend of lower pH and greater water dispersible clay percentage. Porosity varied within the porosity samples due to the presence of dense clay/silt bands （〈 0.5 mm in width） with relatively few air vesicles. The porosity samples with horizontal slices of low porosity （but large numbers of air vesicles） had low infiltrability, while those without slices of low porosity （and relatively few air vesicles） had high infiltrability. We conclude that the intense crusting and resultant low infiltrability of soils in the Knersvlakte appears to be related to the formation of thin, dense clay/silt bands in the pedoderm. 相似文献
10.
奎屯河流域水土中氟的分布规律 总被引：6，自引：0，他引：6
通过对奎屯河流域包气带土壤和地下潜水取样分析,发现从山前洪积砾质倾斜平原到冲洪积平原,氟质量浓度的迁移分布明显具有淋溶-径流、径流-淋溶蒸发、溶滤-强烈蒸发浓缩3个水文地球化学分带。氟质量浓度在细粒粘土粉土层中相对较高,而在砂层中相对较低,无论属于哪种岩性结构在地下潜水位附近氟含量都相对较高。该流域内3条河流氟质量浓度均为上游低下游高,且在流域上游增幅相对较小而在下游增幅相对较大。环河道由近河岸到远河岸水土中氟质量浓度也逐渐增加。初步分析认为,该内陆平原地区氟的富集是以蒸发浓缩作用为主。运用热力学理论进行了验证,水土中氟的水平分布规律是一致的,并可相互转化。 相似文献
11.
沈阳市第四纪沉积物分布广泛，北东薄、南西厚。沉积物类型基本为多层砂土复合结构：地表仅有一层较薄的粘土层，其下为较厚的多层递变的细中砂、粗砂、砾砂、圆砾或卵石层。各土层工程地质性质良好，沈阳市区可适合建筑各种类型的建筑物，选择箱形基础形式及桩基础形式较为合适。 相似文献
12.
The motion forms (deformation) of the sliding soil along the slope include inviscid particle flow, viscous particle flow, and mass sliding. The motion forms were mainly influenced by the mechanical properties of the viscous mud medium filling. The effect of the medium filling on the motion forms of the sliding soil is worth discussing. The sliding soil can be seen as the mixture which is composed of the medium filling and coarse particles. The Chengdu clay with different moisture contents were selected as the medium filling. Their mechanical parameters were experimentally measured for simulating the moving process of the sliding soil. Different motion forms of the sliding soil were numerical simulated based on PFC3D by changing the specific mechanical parameters. The mechanical parameters of the Chengdu clay are experimentally determined. The numerical results show that with the moisture content of the filling slurry medium in the range of >302%, 101%~182%, and <80%, the motion form of the sliding soil belongs to the inviscid particles flow (similar with the sliding sand), viscous particles flow (seen as the viscous flows); and mass sliding (seen as the block sliding along the slope surface), respectively. 相似文献
13.
《中国海洋大学学报(英文版)》2021,(5)
A flume experiment was conducted to investigate the restratification of liquefied sediment strata under a wave load with the focus on the interbedded strata of coarse and fine sediments formed in estuarine and coastal areas. The aim of this research was to study the characteristics and processes of liquefied sediment strata in terms of wave-induced liquefaction. In the experiment, the bottom bed liquefied under the wave action and the liquefied soil moved in the same period with the overlying waves, and the track of the soil particles in the liquefied soil was an ellipse. The sand layer consisting of coarse particles in the upper part, settled into the lower silt layer. The sinking of coarse particles and upward migration of the fine particles of the lower layer induced by liquefied sediment fluctuations are the likely reasons for sedimentation of the sand layer in liquefied silt. 相似文献
14.
裂缝是断溶体油藏的重要渗流通道,随着地层流体的采出,裂缝将发生闭合,其在地应力作用下的闭合规律对于储层渗透率具有重要影响。采集碳酸盐岩岩样,通过巴西劈裂实验制备裂缝试件,构建基于CT扫描灰度图像的裂缝变形分析方法,通过加压和卸压试验,研究裂缝在被不同填充物填充条件下的闭合规律,裂缝的闭合情况采用岩心渗透率和裂缝开度综合表征,以此研究裂缝填充物性质对裂缝闭合规律的影响。研究结果表明:随着围压的增大,裂缝开度和试件渗透率均逐渐降低;填充物延展性越强,裂缝在压力作用下闭合越明显,渗透率降低幅度越大;对于同样被石英填充的裂缝,不同的填充方式下裂缝闭合规律不同,对于裂缝的支撑效果,单层细砂>厚层细砂>中砂细砂混合（结果）。研究成果可为认识不同矿物填充裂缝在地应力作用下的闭合规律提供参考。 相似文献
15.
《山地科学学报》2021,(9)
Soil shrinkage is an important factor in slope destabilization in granitic areas, which is also one of the most important conditions for the formation of permanent gullies. This study explored the effect of soil shrinkage on permanent gullies, and Benggang erosion in granitic areas in southeastern China was used as an example. Three types of Benggang in granitic area were selected to examine the soil shrinkage of three soil layers(the lateritic, transitional and sandy layers) and their effect on the development of Benggang erosion was studied. The results show that the maximum values of COLEH and COLEV(coefficient of linear extensibility in horizontal and vertical directions, respectively) are 3.09% and 1.60% in the laterite layers, 2.71% and 2.13% in transition layers, and 1.10% and 1.82% in sandy layers, indicating that the shrinkage potential of the soil layers exhibits the following order, from highest to lowest: the laterite layer, transition layer, and sandy layer. With a decreasing volumetric water content, the linear shrinkage ratio increases gradually and eventually stabilizes, and in the laterite, transition and sandy layers, the average values of the maximum linear shrinkage are 1.50%, 2.09%, and 1.74%, respectively. Axial shrinkage is most obvious in the transition layers, in which the volume change in the form of subsidence is greater than that in other layers. The soil shrinkage curves fit the trilinear model(R20.9), and the soil shrinkage characteristic curves were divided into structural, basic, and residual sections. The correlation analysis shows that the soil shrinkage rate is positively correlated with clay and Fe_2 O_3 content and negatively correlated with sand content. Clay and sand contents are the most important factors influencing soil shrinkage. Soil oxides can influence soil shrinkage by affecting the particle composition of the soil, so soil shrinkage is closely related to soil clay minerals. Our findings can provide a theoretical basis for revealing the mechanism of Benggang erosion and its control. 相似文献
16.
引碧入连工程，大沙河倒虹吸地质条件复杂，岩性多为淤泥质土和中细砂，前者地基承载力不及８０ｋＰａ，后者有严重的砂土液化问题，为此采用了复合地基处理，提高了地基强度又防止了砂土液化，在施工中应用了静载荷及动力法进行了检测，肯定了复合地基的有效性。 相似文献
17.
在三轴条件下,对饱和土(砂土和黏土)进行排水与不排水条件下的冲击试验及冲击后再固结试验,对比研究了不同渗透性土在不同排水条件下的冲击动力响应和冲击后再固结性状.结果表明:饱和黏土不排水冲击时的孔隙水压力随冲击击数增加而升高并逐渐稳定,排水冲击时的孔隙水压力则是先达到峰值然后有所下降;砂土不排水冲击时的冲击能量对孔隙水压力影响最明显;饱和砂土不排水冲击时的轴向应变与冲击击数呈近似线性关系,饱和黏土冲击及饱和砂土排水冲击则呈近二次曲线关系;饱和砂土不排水冲击后再固结阶段的孔隙水压力立即消散为0,同时体变迅速增大到一定值;饱和黏土在冲击后再固结阶段的孔隙水压力在一定时间内逐渐消散完毕,同时体变逐渐增大;饱和黏土排水冲击时,冲击阶段产生的体变占冲击引起总体变的39%~49%,冲击后再固结阶段产生的体变占51%~61%;砂土和黏土的总体变均表现为排水冲击明显大于不排水冲击,改善冲击时的排水条件有利于提高加固效果. 相似文献
18.
Alexander Tsatskin Tatyana S.Gendler Friedrich Heller Igal Dekman Gitti L.Frey 《山地科学学报》2009,6(2):113-124
The paper addresses the controversial question of the role of clay-sized dust in the formation of paleosols in coastal eolianites, Israel. At the Habonim type section, the pedocomplex dated by archaeology and luminescence to 45-135 ka ago shows at least three paleosols, not separated by non-soil sediments. The oldest reddish paleosol （apparently related to MIS 5） is magnetically enhanced, leached from carbonates, with signs of bioturbation and strongly aged clay coatings. The reddening is due to very fine, -20 nm, poorly crystallized, superparamagnetic （SP） hematite, as determined by Mossbauer studies. In subsoil, lithorelics of eolianite are found. Over time, the soil surface aggraded due to accelerated fine dust accumulation alongside local slope wash. On younger materials formed magnetically depleted vertisols, dominated by smectite-type expandable paramagnetic clays. In thin sections, vertisols exhibit strong stipple-speckled and striated b-fabric due to shrink-swell processes, impregnative calcite nodules and Fe-Mn redistribution. The uppermost hydric vertisol shows the strongest expression of juxtaposed features of recurrent calcite and Fe precipitation. This paleosol developed on colluvial soil materials, as evidenced by mixing of clay coated and uncoated grains of quartz and calcite allochems. M6ssbauer spectra show high amounts of Fe（III） incorporated in the clay structure, low amounts of SP goethite and absence of SP hematite. Whilst magnetic susceptibility drops in vertisols to minimal values, increase. The latter along ferrimagnetie grain sizes with differences in the hierarchy of microfabric features is taken as indication for lithologic discontinuities which may have resulted from continuous, albeit variable and low-intensity, input of eolian clay from both remote Saharan and local sources, roughly dated to the earlier to middle part of the Last Glacial. 相似文献
19.
This research paper analyses the grain-size characteristics of the Quaternary deposits at Xingshan near Siping, Jilin province in China by employing graphic measures to study the grain size distribution and its mode of transport and deposition. The Quaternary deposits at Xingshan lie unconformable on Cretaceous rocks made of siltstone, mudstone and sandstone. The average grain size is between 8.06 to 8.55Φ (0.002 6 ～0.003 7 mm). The Quaternary deposits at Xingshan mainly compose of very fine silt to clay. The compositions of the grade are clay 63% and silt 37%. The clay size components are weathered debris transported and deposited by flowing water from the SE highlands or hills to the low lying NW Xingshan plains whereas the silty components accumulated by aoelian process. The Quaternary deposits at Xingshan accumulated in the middle and late Pleistocene interglacial periods from (459.12～39.03) ka to (88.92～7.56) ka. The standard deviation ranged from 0.96 to 1.36Φ, indicating that the sediments are moderately to poorly sorted, Coefficient of skewness ranged from 0.16～0.31 with an average skewness of 0.218, (Positively skewed towards fine). Kurtosis values (0.84～1.05) from the grain size distribution and visual inspection of the frequency curves indicate platykurtic to mesokurtic curves and unimodal to bimodal grain-size distribution. The type of deposit formation is sand dune and the source is at a distal from its provenance. 相似文献
20.
Experimental analysis of shear strength of undisturbed soil in leucaena forest in Jiangjia Ravine,Yunnan, China 总被引：1，自引：0，他引：1
Five leucaena trees of similar age were chosen in Jiangjia Ravine of Dongchuan, Yunnan Province, China, near which the soil samples were
collected by digging profiles 2m in depth and 1m in width. In each section, soil samples at different depths were taken for
direct shear experiments to determine the root amount and mechanical composition. It is found that the cohesion and internal
friction angle of the undisturbed soil are related to the root amount, depth, clay content and breccias content. Cohesion
correlates negatively with root content, a finding that differs from that of other researchers. In addition, internal friction
angle correlates positively with all these factors. 相似文献