共查询到20条相似文献，搜索用时 31 毫秒
1.
The mechanical property of saline soils varies with moisture and climate in the cold and salt lake region of Qinghai-Tibet Plateau, which influences
project construction. In order to improve foundation reinforcement effect of the Qarhan–Golmud Highway, Qinghai Province,
China, dynamic compaction replacement (DCR) composite foundation was applied in saline soils. A field experiment was conducted in this
area, where strength and working mechanism of pier-soil and deformation modulus of the composite foundation was analyzed after reinforcement.
This paper presents methods for determining the coefficient on the bearing capacity evaluation and deformation modulus of
composite foundation with DCR. Reinforcement case of DCR is highly effective in saline soils of the salt lake regions, which helps the migration
of water and salt in saline soils. 相似文献
2.
Extensive studies of land subsidence in the Yellow River Delta (YRD) have identified sediment consolidation and compaction as important contributors to geologic processes. Although previous studies were informed by detailed knowledge of subsurface getechnical properties and depositional history, geotechnical data that are sufficient for detailed modeling are still unavailable for much of the delta. To overcome this limitation, we use a modified Monte Carlo method to model the incremental sedimentation and compaction in the delta and identify the stratigraphic characteristics of all abandoned lobes in the delta on a short-term scale of decades. A Digital Elevation Model (DEM) of the thickness of the delta plain is generated based on a contour map of the delta using Geographic Information Systems technology. Combining our simulation results and the DEM creates an overall view of the delta’s temporal and spatial land subsidence characteristics. Most data from the 152 boreholes show properties of soft soil, which is saturated and compressible. Our data confirm that the most rapidly compacting strata contain 100% soft soil. Research on settlement from soft soil compaction is particularly important because of the widespread distribution of soft soil in the YRD. 相似文献
3.
Neil M. Ribe 《Geophysical Journal International》1985,83(2):487-501
Summary. The segregation of melt from a partially molten source region requires a corresponding deformation of the unmelted residue ('matrix'). The role of matrix deformation during melt segregation is examined using simple one-dimensional models, for which the deformation consists only of bulk compression or 'compaction'. In model I, a volume fraction φ0 of ascending mantle material undergoes pressure-release melting at a depth z = 0 (localized melting). Compaction of the matrix occurs in a boundary layer whose thickness (reduced compaction length δR ) is proportional to the square root of the matrix viscosity. In the Earth's mantle, δR ∼ 10–100 m, indicating that compaction cannot be important over large distances. Model II examines the case in which melting occurs over a depth range of order h (distributed melting). In the limit h ≪δR , the solution is the same as for the case of localized melting, except in a 'melting layer' of thickness ∼ h near z = 0. In the more realistic limit h ≫δR , compaction makes a negligible contribution to the balance of forces associated with melt segregation. This result is also valid for the more general case of two-dimensional flow. Compaction is therefore likely to be of negligible importance in the Earth's mantle, with the consequence that melt segregation can be accurately described by Darcy's law. 相似文献
4.
Gokhan Baykal 《寒旱区科学》2015,7(5):619-625
The construction period in cold regions is very short due to problems related to excavation and use of frozen soils in embankment construction, which leads to excessive deformations upon thawing. Also, handling of compaction water is critical due to freezing temperatures. Coalburning thermal power plants are very common in cold regions to supply electricity. The inorganic part of the pulverized coal after burning produces fly ash, which is available in large volumes. Due to excavation difficulties and the poor engineering behavior of frozen soils in cold regions, the utilization of fly ash when it is readily available must be promoted. Any construction technique which utilizes alternative materials like fly ash and minimizes water consumption has a potential to extend the short construction season and even allow service and maintenance during extreme weather conditions. This paper presents two potential techniques to solve the moisture affinity of silt-sized materials like fly ash. One technique involves in-plant production of fly ash pellets using cold-bonding pelletization to manufacture aggregates of up to 40,000-μm diameter from 15- to 60-μm-diameter fly ash grains. Large disc pelletizers have annual production capacities of up to one million ton at a reasonable cost. The product has adequate strength for embankment construction even when no water is used and no compaction is applied. The second technique is an in situ mixing technique which uses snow instead of compaction water for fly ash. The snow is the main element in this technique to compact the embankment. Water is needed for the hydration reactions to form cementitious minerals in fly ash. The slower the hydration reaction, the greater the crystal growth of cementitious minerals. In the proposed technique, in situ snow is mixed with fly ash and is compacted on-site. The temperature increase due to the hydration reaction of fly ash upon contact with snow crystals provides water for continued long-term hydration, which results in high strength, a high void ratio, light weight, and high thermal insulation capability. The presented techniques have the potential to extend the short construction season in cold regions and will provide fill material, decreasing the need for excavation. Both techniques are well documented under laboratory conditions, the research results have been published, and the techniques are ready for field trials to assess implementability. 相似文献
5.
Fine round gravel soil is widely employed in the subgrade of high speed railways in cold regions to prevent frost heaving
and thawing. The lower the fines content in fine round gravel soil, the smaller the quantities of frost heaving and thawing,
but compaction difficulty increases. This study is to obtain the optimum fines content and limited frost heaving and
thawing. The fine round gravel soil filling (FRGSF) used in the Harbin-Qiqihaer Passenger Dedicated Line is taken as the
study object. Influence of fines content on optimum water content, maximum dry density and frost heaving properties of
FRGSF were studied by means of compaction and frost heaving tests. Results show that the maximum dry density of the
FRGSF increases first and then decreases with an increase of fines content, namely there is an optimum fines content for
easy compaction. The method of surface-vibratory instrument is fit for coarse-grained soils, and wet state of
coarse-grained soil is in favor of compaction. Considering the relationship of fines content with maximum dry density and
the frost heaving ratio of FRGSF, the fines content should be limited to within the range of 9%-10%, so that the frost
heaving ratio is less than 1%, and the FRGSF is easily compacted. Water supply is proved to be an important factor influencing
the amount of frost heaving of FRGSF. We also conclude that in the field, it is imperative to control waterproofing
and drainage measures. 相似文献
6.
Because ice-high foundation soil is widely distributed in permafrost regions,the correct preparation of ice-high specimens is of critical interest in engineering design for foundation stability.Past research has shown that the uniaxial compression strength of ice-high frozen soils changes as the ice or total water content increases; the differences of different methods of specimen preparation are analyzed here and the advantages and disadvantages of them are presented.It is confirmed that the role of crushed ice is significantly different from that of naturally frozen ice in frozen soils,and the size and amount of crushed ice will influence the strength and deformation mechanism of frozen soils.Therefore,it is strongly recommended that when a ice-high specimen is artificially prepared,the ice should be frozen through natural means and not be replaced with crushed ice. 相似文献
7.
察尔汗盐湖地区盐渍土微观结构及其力学与强度表现 总被引：2，自引：0，他引：2
为探明察尔汗盐湖区盐渍土的微观结构特征及其力学与强度表现,从盐湖区采集9组不同含盐量的盐渍土样品,对盐渍土进行电镜扫描、直接剪切试验和抗压强度试验,从微观结构上分析了盐渍土的力学与强度表现,提出了察尔汗盐湖区盐渍土颗粒骨架的连结形式。研究结果表明,不同含盐量的盐渍土微观结构形式不同,盐渍土颗粒骨架之间的连结有3种形式:1)点式接触、2)堆叠接触、3)盐晶体胶结;微观结构越密实,盐晶体胶结作用越强,盐渍土表现出越高力学与强度特性;盐晶体的胶结作用是影响盐溃土力学与强度特性的显著因素;无侧限抗压强度显著变化的含盐量拐点为45.74%。 相似文献
8.
《Basin Research》2018,30(Z1):424-436
Industry 2D and 3D seismic data across the North Taranaki Basin displays two listric normal faults that formed during Pliocene shelf edge clinoform progradation. The faults die out in the down‐transport direction with no evidence for contractional structures, except for two small thrust faults in one narrow zone. When active, the detachments lay at depths of about 1000 m below the seafloor. The overlying section had high initial porosities (30–60%). It is estimated that loss of about 17–20% pore volume by lateral compaction, and fluid expulsion over a distance of about 4–6 km in the transport direction occurred in place of folding and thrusting. Seismic and well evidence for abnormally highly compacted shales suggests there is about 6% less porosity than expected for in the prekinematic section, which possibly represents a residual of the porosity anomaly caused by lateral compaction. The observations indicate significant shortening (~20%) by lateral compaction and probably some layer parallel thickening are important deformation mechanisms in near‐surface deepwater sediments that needs to be incorporated into shortening estimates and ‘balanced’ cross‐sections. A key factor in listric fault initiation near the base of slope is inferred to be transient, increased pore fluid pressure due to lateral expulsion of fluids from beneath the prograding Giant Foresets Formation. 相似文献
9.
This paper set up a series of comprehensive targets based on the concept of 'anti-freeze filler', which include reasonable water retention rate, frost heave characteristics, and compaction characteristics of filling material. Then, a type of permeable graded gravel is proposed, suitable for high-speed railway subgrade. A series of in-door water retention, permeability, and frost heave tests were performed under different graded conditions. Water retention, permeability, and frost heave characteristic of different graded filling materials can be determined, in order to define the gradation range of permeable graded gravel. Relying on the frost-heave monitoring record of high speed railway in Northeast China, a series of experimental studies were performed, which included on-site filler production, compaction test, and the anti-frost effect test, in order to improve the production and compaction techniques of permeable graded gravel. From the research of this paper, the use of permeable graded gravel subgrade as the anti-frost structure for the high-speed railway subgrade in cold areas is feasible. 相似文献
10.
Frost heave is one of the major complications in highway construction in cold regions. Laboratory experiments are im-portant in the study frost heave behavior of soils, and one-dimensional frost heave ... 相似文献
11.
土壤紧实度对马铃薯根系、匍匐茎、产量和品质的影响 总被引：4，自引：0，他引：4
使用外力压迫砂柱的盆栽方法,研究了土壤紧实度分别为0.79 MPa（T1）、0.98 MPa（T2）和1.24 MPa（T3）的基质对马铃薯品种夏波蒂、陇薯8号和青薯9号的根系及匍匐茎形态、块茎产量及其品质的影响。结果表明：（1）随土壤紧实度增大,马铃薯根系与地上部干重下降,根冠比升高,根系表面积与总长度减少,而根系平均直径增大;（2）土壤紧实度增大导致匍匐茎的纵向伸长、直径增加,三个品种匍匐茎长度和直径与对照T1相比差异达到显著水平（P<0.05）;（3）三个品种块茎产量在T2处理下较对照T1差异不显著（P<0.05）,而在T3处理下的块茎产量较对照相比达到差异显著水平（P<0.05）,随土壤紧实度增大三个品种的商品率均低于对照T1,且达到显著差异水平（P<0.05）;（4）块茎干物质与淀粉含量增加,粗蛋白与还原糖含量下降,维生素C含量无显著性变化。紧实土壤不利于马铃薯根系、匍匐茎以及块茎的生长发育,也影响了品质的整体提高。 相似文献
12.
This article provides an overview of several previous studies that investigated the stiffness and strength performance of chemically stabilized roadway materials under winter conditions (freeze-thaw cycling). The objective of this research was to understand the behavior of different materials stabilized with different type of binders when they were subjected to freeze-thaw cycling. Nine different materials including natural soils (organic soil, clay, silt, sand, and road surface gravel), reclaimed pavement material, and recycled asphalt pavement stabilized with nine different binders (five different fly ashes, lime, cement, lime kiln dust, cement kiln dust) were discussed. This article investigated how the volume, resilient modulus and unconfined compressive strength of soils/materials stabilized with different binders change in response to freeze-thaw cycling. Overall, the review results indicate that the stiffness and strength of all stabilized materials decrease somewhat with freeze-thaw cycling. However, the reduced strength and stiffness of stabilized materials after freeze-thaw cycling was still higher than that of unstabilized-unfrozen original soils and materials. In addition, materials stabilized with cement kiln dust provided the best performance against freeze-thaw cycling. 相似文献
13.
In order to improve the engineering stability of saline soil of high chloride content in the Chaerhan salt lake region, six typical characteristics saline soil samples were selected, and tests on their... 相似文献
14.
S. van Asselen 《Basin Research》2011,23(2):239-255
Provision of accommodation space for aggradation in Holocene deltaic basins is usually ascribed to eustatic sea‐level rise and/or land subsidence due to isostasy, tectonics or sediment compaction. Whereas many Holocene deltas contain peat, the relative contribution of peat compaction to total subsidence has not yet been quantified from field data covering an entire delta. Subsidence due to peat compaction potentially influences temporal and spatial sedimentation patterns, and therefore alluvial architecture. Quantification of the amount and rate of peat compaction was done based on (1) estimates of the initial dry bulk density of peat, derived from a relation between dry bulk density and organic‐matter content of uncompacted peat samples and (2) radiocarbon‐dated basal peat used to reconstruct initial levels of peat formation of currently subsided peat samples. In the Rhine‐Meuse delta, peat compaction has contributed considerably to total basin subsidence. Depending on the thickness of the compressible sequence, weight of the overburden and organic‐matter content of peat, subsidence of up to approximately 3 m in a 10‐m thick Holocene sequence has been calculated. Calculated local subsidence rates of peat levels are up to 0.6 mm year?1, averaged over millennia, which are twice the estimated Holocene‐averaged basin subsidence rates of 0.1–0.3 mm year?1 in the study area. Higher rates of subsidence due to compaction, on the order of a few mm year?1, occur over decades to centuries, following a substantial increase in effective stress caused by sediment loading. Without such an increase in effective stress, peat layers may accumulate for thousands of years with little compaction. Thus, the contribution of peat compaction to total delta subsidence is variable in time. Locally, up to 40% of total Holocene accommodation space has been provided by peat compaction. Implications of the large amount of accommodation space created by peat compaction in deltaic basins are: (1) increased sediment trap efficiency in deltas, which decelerates delta progradation and enhances the formation of relatively thick clastic sequences and (2) enhanced local formation of thick natural levees by renewing existing accommodation space. 相似文献
15.
Henk Kooi 《Basin Research》1997,9(3):227-241
The method of indirect demonstration is used to investigate if compaction disequilibrium can account for high overpressures that occur in Mesozoic and older basin formations. First the equations governing compaction disequilibrium are analysed for the factors controlling overpressure levels. Then limiting values of these control parameters are sought which favour high fluid pressures. The analysis shows why 'close-to-lithostatic fluid pressures' in pre-Cenozoic basin units are difficult to attain by compaction disequilibrium alone. Subsequently, the limiting favourable conditions are used in a series of generic numerical model experiments. The experiments serve as templates to construct the upper bounds of overpressures due to sediment loading for most geological settings including those where shale seals have developed. Two regional examples are studied in some detail. It is shown that observed overpressures in Mesozoic strata on the Scotian Shelf can be explained by compaction disequilibrium, but require the limiting values assigned to the properties of shale. For the Central North Sea Graben these limiting conditions are not sufficient, providing evidence for an active role of other pressure-generating mechanisms.
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16.
西南地区水耕人为土诊断层土壤特性及SEM特征 总被引：3，自引：0，他引：3
对我国西南地区代表性水耕人为土诊断层土壤特性进行研究,并采用扫描电镜(SEM)进行土壤微形态研究,结果表明:不同母质和发育程度的水耕人为土,在土壤特性及在剖面上的变化特征都有明显差别.通过SEM观察研究表明:粗、细颗粒物质形态与矿物组成密切相关,如以薄片状、针条状等细粒物质为主的土壤,在水耕条件和外力作用下,易于定向、粘结聚合而引起土壤压实和板结.水耕人为土的微团聚体含量少而分散,对肥力的贡献有限.长期培肥的水耕人为土能够形成丰富的各类微孔隙和微结构类型,是调节土壤水、热、气和养分状况的主要机制. 相似文献
17.
Processes and mechanisms of multi-collapse of loess roads in seasonally frozen ground regions: A review 总被引：1，自引：0，他引：1
Usually, the collapsible loess widely distributed across the world can serve as a type of foundation soil that meets its strength requirement after dense compaction and elimination of collapsibility. However, many problems such as cracks and differential settlement still occur in loess roads in the seasonally frozen ground regions after several years of operation. Many studies have demonstrated that these secondary or multiple collapses primarily result from the repeatedfreezing-thawing, wetting-drying, and salinization-desalinization cycles. Therefore, we conducted a research program to (1) monitor the in-situ ground temperatures and water content in certain loess roads to understand their changes, (2) study the effects of freezing-thawing, wetting-drying, and salinization-desalinization cycles on geotechnical properties and micro-fabrics of compacted loess in the laboratory, and (3) develop mitigative measures and examine their engineered effectiveness, i.e., their thermal insulating and water-proofing effects in field and laboratory tests. Our results and advances are reviewed and some further research needs are proposed. These findings more clearly explain the processes and mechanisms of secondary and multiple collapse of loess roads. We also offer references for furtherstudy of the weakening mechanisms of similar structural soils. 相似文献
18.
古尔班通古特沙漠风沙土土壤蒸发特征 总被引：10，自引：2，他引：10
土壤表面蒸发是降水的无效损失,其大小直接决定着降水转化为有效土壤水的效率,从而间接决定了植物可利用水分的多寡。在降水稀少的沙漠区,定量认识土壤蒸发的大小和其所占降水的比例显得尤为重要。在2004年全生长期(5~9月)应用自制的微型蒸渗仪(Micro-Lysime-ter)测定了风沙土(有结皮覆盖的丘间低地和裸露沙丘顶部)和对照的荒漠盐碱土的土壤蒸发。结果表明:在相似的气象条件下,风沙土区的丘间低地和荒漠盐碱土的日平均蒸发量分别约是裸露沙丘(风沙土区)的2倍和3倍。整个生长期裸露沙丘的累积蒸发量为18.7mm,丘间低地为38.8mm,荒漠盐碱土为52.1mm。根据整个观测期的累积蒸发量和累积降雨量计算得出的蒸发降雨比分别为:裸露沙丘0.20,丘间低地0.42,荒漠盐碱土0.62,表明裸露沙丘由降水转化为土壤水而储存的比率最高。同时,从数据分析中可以看出:在风沙土区0~5cm土层的含水量对土壤蒸发起决定作用,而盐碱土区的土壤蒸发则受到更深层次土壤水分的影响。裸露沙丘低的土壤蒸发、高的降水转化效率,为植被恢复奠定了良好的基础。因此,裸露沙丘的低蒸发量可以视为植被状况对生态水文过程的一种良性反馈。 相似文献
19.
Quantifying the contribution of tectonics vs. differential compaction in the development of domes along the Mid-Norwegian Atlantic margin 总被引：1，自引：0，他引：1
A sequential restoration based on combined backstripping and unfolding methods affords the opportunity to study the Cenozoic evolution of two low amplitude domes in the Mid‐Norwegian extensional margin, the Helland Hansen Arch and the Vema Dome. The integration of growth strata geometries observed in both flanks of the domes demonstrate that the structures grew by a variable combination of tectonics and differential compaction mechanisms. Sequential restoration shows that the Helland Hansen Arch grew between Early Oligocene and earliest Late Pliocene times (33–1.9 Ma). During the first phase of growth (33–9 Ma), the tectonic compression accounted for a minimum of 27% of the total dome amplitude. During Late Miocene to Pliocene times (9–1.9 Ma), differential compaction was the mechanism for dome growth. During Late Pliocene times, the Helland Hansen Arch grew with the highest rates coinciding with initial deposition of prograding wedges (3.6–1.9 Ma). In contrast, the Vema Dome started to develop in Early Eocene times and grew at a fairly constant rate up to Early Pliocene times at 3.6 Ma. The amplification of the Vema Dome took place through both differential compaction and tectonics between Early Eocene and Late Miocene times (54.8–7 Ma). The tectonic contribution accounted for a minimum of a 37% of the total dome amplitude. During Pleistocene times, the progradation of clastic wedges led to a decrease of the amplitudes of both the Helland Hansen Arch and the Vema Dome. The different timing of tectonic growth for analysed domes and arches suggest that a small and protracted phase of compression affected the Mid‐Norwegian Margin. This agrees with well‐known widespread contractional deformation affecting the Atlantic Margin of the European Plate during the Tertiary. 相似文献
20.
对南方丘陵区3种不同母质水稻土时间序列黏粒矿物的X-射线衍射（XRD）进行分析发现：① 紫色砂页岩（PS）母质起源土壤的黏粒矿物以高岭石类似矿物为主;第四纪红黏土（RC）母质起源土壤的黏粒矿物以高岭石类似矿物、伊利石类似矿物与三羟铝石为主;红砂岩（RS）母质起源土壤的黏粒矿物以1.4 nm过渡矿物、高岭石类似矿物与三羟铝石为主。② 这3种母质土壤种稻后黏粒矿物的变化大体可分为2种情况。RC与RS母质的起源土壤种稻后,土壤黏粒矿物的变化相对较小,伊利石类似矿物相对含量有所增加,这可能主要与钾肥的持续施用有关。PS母质的起源土壤种稻后,土壤黏粒矿物变化相对较大,表现为高岭石类似矿物相对含量降低,低结晶度的伊利石或次生绿泥石与三羟铝石相对含量上升。PS母质发育的土壤种稻后脱钾明显且主要集中在原生矿物部分。这种原生矿物的脱钾作用对土壤黏粒含量和黏粒矿物的类型都有较大影响。③ 起源土壤的黏粒矿物通常会被水稻土所继承,并在水稻土发育过程中相对稳定,可以用其来指示起源土壤（或母质）的物源组分。 相似文献