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1.
This paper aims to determine the optimal fines content of coarse-grained soil required to simultaneously achieve weaker frost susceptibility and better bearing capacity. We studied the frost susceptibility and strength properties of coarse-grained soil by means of frost heaving tests and static triaxial tests, and the results are as follows:(1) the freezing temperature of coarse-grained soil decreased gradually and then leveled off with incremental increases in the percent content of fines; (2) the fines content proved to be an important factor influencing the frost heave susceptibility and strength properties of coarse-grained soil. With incremental increases in the percent content of fines, the frost heave ratio increased gradually and the cohesion function of fines effectively enhanced the shear strength of coarse-grained soil before freeze-thaw, but the frost susceptibility of fines weakened the shear strength of coarse-grained soil after freeze-thaw; (3) with increasing numbers of freeze-thaw cycles,the shear strength of coarse-grained soil decreased and then stabilized after the ninth freeze-thaw cycle, and therefore the mechanical indexes of the ninth freeze-thaw cycle are recommended for the engineering design values; and (4) considering frost susceptibility and strength properties as a whole, the optimal fines content of 5% is recommended for railway subgrade coarse-grained soil fillings in frozen regions. 相似文献
2.
利用2015年9月采自青海北霍布逊湖区的原土样,自行配比进行了室内盐渍细砂土冻胀试验,研究了低干密度盐渍细砂土的低温特性变化规律,探讨了盐渍细砂土的冻胀机理,集中分析了土的冻缩特性。研究发现低干密度盐渍细砂土在不同含水率条件下土的冻胀规律差异很大。低含水率条件下会有冻缩现象,高含水率条件下只会有冻胀现象,临界含水率（含水率14%）条件下细砂土先出现冻缩,之后随着温度的降低又出现冻胀,且由于温度引起的体积变化均在-28℃～-30℃时达到稳定;土的冻缩随着含盐量增加先呈递增趋势,后又呈递减趋势,在中间含盐量10%达到最大;除临界含水率条件下,盐渍细砂土的冻胀、冻缩均与温度呈三次多项式关系,与含水率呈线性关系。研究结果能够为盐渍土地区的工程建设提供有价值的理论依据。 相似文献
3.
干密度是评价软土固化质量的重要指标,一般通过室内击实试验获得。以氯氧镁水泥(MOC)为结合料,砾石土为固化对象,研究了原料配比对MOC固化砾石土击实性能的影响。通过室内击实试验,考察了轻烧镁粉掺量、卤水浓度、卤水掺量和活性MgO/MgCl_2物质的量比(Mg/Cl比)影响混合料干密度的规律。结果表明:MOC固化砾石土击实料的干密度随卤水掺量增加先增加后降低,随轻烧镁粉掺量及Mg/Cl比的增加而先增加后降低,随卤水浓度及轻烧镁粉掺量的增加而增加,随卤水浓度增加及Mg/Cl比降低而增加。 相似文献
4.
Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tunnels excavated in fractured rock mass in cold regions under different constraints and freezing depths were studied by a test model. It was found that the larger the frozen depth, the larger the frost heaving pressure, and the stronger the top constraint, the larger the frost heaving pressure. For the horseshoe lining and city-gate lining, the top constraint has a greater effect on the frost heaving pressures on the arch and the inverted arch. For the round lining, the influences of the top constraint on the frost heaving pressure in all linings are almost the same. The frost heaving pressure is maximum on the city-gate lining and minimal on the round lining. The largest frost heaving pressure all occur near the foot of the inverted arch for the three kinds of lining. Thus, the test data basically coincide with the observed in situ data. 相似文献
5.
古尔班通古特沙漠砂的物理力学性质 总被引：7，自引：2，他引：5
野外勘察和大量物理力学性质试验结果表明,古尔班通古特沙漠砂的厚度一般小于200m。粒径较均匀,控制粒径(d60)变化范围在0.12~0.25之间,由北至南,从上到下砂粒直径略有减小。在天然状态下,沙漠砂含水量1%~2%,干密度1.55~1.62g·cm-3,中密状态,低压缩性,渗透系数2.0×10-2~4.0×10-3cm·s-1,临界破坏比降0.9~1.7,破坏形式为流土。抗剪强度指标c=5.0~14.0kPa,φ=29°~34°。承载力特征值100kPa。天然状态的沙漠砂按冻胀率划分为不冻胀性砂,当含水量小于18%时,为不冻胀或弱冻胀性砂。当砂在饱和状态时为冻胀性砂。沙漠砂力学性质的变化主要受干密度和含水量的影响。干密度越大,含水量越小,其力学性质越好。对于沙漠工程,提高沙漠砂的干密度,做好构筑物的防渗排水,避免地基含水量增高,是保证工程设施安全、正常运行的关键。 相似文献
6.
Frost heaving is a well-known phenomenon in cold regions, which may occur in wet clayey grounds during winter. Railway track upheaval occurring in cold regions during the winter is generally understood as frost heaving in the subgrade layer. However, it has been confirmed that upheaval due to frost heaving sometimes occurs in the ballast layer. This understanding has been observed in active railways in northern Japan. The samples collected from ballast and subgrade layers have been examined for frost heave susceptibilities and confirmed that ballast layers which contain fines may heave. 相似文献
7.
A new experiment method is introduced to study the relations between frost heaving strain and stress of soil or fracture rock under different moisture contents, temperatures and stress states. Based on experiments, a new triaxial frost heaving stress-strain relation is presented aiming at tunnel in cold regions. The experimental equipments are strain-controlled and low temperature buildup, and different restrained conditions are controlled by changing the stiffness of a test-force-ring. Then the frost heaving strain and stress of soil or fracture rock can be obtained under different restrained conditions, and the frost heaving stress-strain relation can be got by regression analysis of some feature points. Experiments of saturated sandy soil conducted by this method show that the triaxial frost heaving stress-strain relation could be expressed by logarithmic curves, and the frost heaving stress changes linearly with the logarithm of the frost heaving strain. The stronger the constraint, the smaller the frost heaving strain and the larger the frost heaving stresses. The frost heaving stresses would tend to a limit value with increasing the constraint intensity. The larger the confining pressure, the larger the frost heaving strain and stress. 相似文献
8.
Frost susceptibility should be considered in the design and construction of foundations and retaining-wall structures in regions with the seasonally freezing-soil ground condition. When planning construction that goes deep into this soil, one has to understand the impact of horizontal forces to an underground wall and realize the potential effect of frost heaving upon, deep foundations. This article presents a few soil tests for frost heaving and the results of those tests show dangerous data for retaining structures under the soil conditions in Kazakhstan. The main parameters of the soil include frost penetration and heaving rate and amount. So, in designing underground structures, one must understand and consider that frost heaving occurs in various directions; this factor is very important for predicting on the restriction of deformations of structures in the seasonally freezing-soil ground condition. 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.
石漠化地区基岩裸露、砾石堆积,水土流失严重,土壤与植被覆盖率低,因此引发一系列的生态恶化问题,而客土恢复植被是一项快速有效的治理途径。本试验在贵州毕节地区实施,以当地黄壤客土(T1,黄壤与砾石比为1∶1;T2,黄壤与砾石比为2∶1;T3,黄壤与砾石比为3∶1;T4,黄壤与砾石比为1∶0)改良石漠化,从耐瘠薄的灌木——沙棘(Hippophae rhamnoides)为试材,探究其幼苗在客土改良后的石漠化土壤中的适应性,栽种期为2年。结果表明:客土处理对沙棘幼苗的冠幅、粗根的根长密度、粗根根重密度均无显著影响;百分之百客土即T4会显著抑制沙棘株高、根系生物量,显著促进细根比根长的增长;当黄壤与砾石比例1/2—2/3时,2年后沙棘细根的根重密度与土壤含水量均会显著增加;当黄壤与砾石比大于2/3时会显著抑制沙棘根系长度总和的增加,且2年后对土壤水分改善作用不显著;沙棘根系指标与2年后的土壤含水量呈现出显著的相关关系。在贵州毕节地区客土改良石漠化时,并非客土越多越好,当黄壤与砾石的比例在1/2—2/3时,栽种沙棘2年可显著改善土壤含水量。 相似文献
11.
In the cold regions of northern China, incidents of municipal underground gas pipeline rupture and leakage occur quite frequently,
most often in winter. To prevent harm to citizen safety and property, analysis of the causes of such cracking and leakage is therefore
valuable. Two incident analyses are discussed here and the reasons why most of these types of cases occur during winter are clarified.
The effects of vehicle loadings above buried pipelines are calculated and compared with the effects and calculations of frost heaving
forces. We demonstrate that when the soil layer above a pipeline freezes rapidly, the soil generates repeated frost heaving, which exerts
heaving forces on the pipeline that can result in fatigue crack propagation and ultimate pipeline failure. Therefore, the incident induced
by frost heaving is one of the primary reasons of gas pipeline failure. Based on these analyses, we present some recommendations
pertaining to the proper design, construction, and management of gas pipelines. 相似文献
12.
Kazakhstan regions is seasonal climatic with transient freezing of soil groundduring the winter. Roadbed integrity is important to resist the sustained load transmitted by traffic on the road surface. Freezing of soil ground could significantlyinfluence roadbed integrity in the seasonal freezing climate of Kazakhstan. The proper determination magnitude of frost heave and heaving pressure by the influence of freezing temperatures during the winter season are necessary for design and construction of highways. Thus, experimental tests were conducted on specimens obtained from Astana (Kazakhstan) to determine the freezing pressure and magnitude of frost heaving. 相似文献
13.
14.
The operation of a railway track in cold regions results in the premature deformation of subgrade soils caused by significant temperature fluctuations and ecological imbalance. Identification and calculation of the thawing degree of permafrost soils, frost heaving of clays, and groundwater flooding require careful engineering and geological surveying. The paper describes the unique, long-standing experience of the university scientists connected with maintaining the Russian East-Siberian and Trans-Baikal Railways'' facilities. Specific features of and requirements for the surveying, depending on the geological and climatic conditions, are identified. 相似文献
15.
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
16.
钙网蛋白（calreticulin,CRT）是参与多种细胞过程的高度保守的内质网伴侣蛋白。1974年,它首次被鉴定为钙离子结合蛋白,随后CRT与肿瘤之间信号通路相关关系被广泛的研究。另外,在人类多种肿瘤中,细胞表面的CRT被认为是1个"促吞噬"信号,由此CRT与癌细胞的巨噬细胞吞噬免疫系统的相关研究,有望为肿瘤综合治疗提供新的理论依据和策略。也有越来越多的证据表明CRT在不同肿瘤中的异常表达,将为CRT成为一种新的肿瘤标志物提供许多依据。以及CRT对各种肿瘤的发展具有很重要的影响且CRT对肿瘤形成和进展的影响取决于细胞类型和临床阶段。 相似文献
17.
Satoshi Akagawa 《寒旱区科学》2021,13(2):77-86
Since the 1970's, frozen ground has been developing near the Tokyo Bay area around liquefied natural gas(LNG) inground storage tanks. For disaster prevention purposes, the tanks are constructed below the ground surface. Since the temperature of the liquid stored in the tanks is -162℃ the soil surrounding the tanks freezes. Since this frozen ground has existed for almost half a century, we have permafrost near Tokyo. The development of artificial frozen ground may cause frost heaving, resulting in frost heave forces that may cause structural damage of adjacent LNG in-ground storage tanks.Therefore, the demand for frozen ground engineering increased and consequently we now have advanced technology in this area. Fortunately, we use this engineering technology and artificial ground freezing for civil engineering, especially in big and crowded cities like Tokyo. This paper provides a summary of the testing apparatus, test methods, and assessment methods for frost heaving. 相似文献
18.
A. AbdelkadirF. Yimer 《Journal of Arid Environments》2011,75(11):1067-1071
This study investigated the effects of land use change on infiltration and moisture content of soils in three land use types. A total of 81 soil and core samples (3 replications × 3 treatments × 3 profiles × 3 soil depths) were used to determine parameters that may affect the infiltration properties of soils. The infiltration rate was measured in the field using double-ring infiltrometer with three replicates in each land use type. Results showed that infiltration rates were generally slow in the open grazed and cultivated lands suggesting high potential for runoff, limited percolation, and very low amount of water available in the soil profiles. The accumulated infiltration in soils under cultivation and open-grazing was smaller than the controlled grazing by approximately 57%. Similarly, cultivation and open-grazing had reduced the soil moisture content by 29 and 33%, respectively, compared to the controlled grazing. Surface soil compaction, higher dry bulk density and lower soil organic carbon, appeared to be the principal factors for the low infiltration capacity and moisture content of the soils. Therefore, dry land management, with long term tree cover and well regulated grazing system, is very crucial for the sustainable ecosystem functioning of this environmentally fragile area. 相似文献
19.
冻融作用与土壤理化效应的关系研究 总被引：19，自引：0，他引：19
冻融使土壤经历一系列物理、化学和生物变化过程,冻融作用对土壤的影响主要表现为:改变土壤结构、含水量分布和水热运动,影响微生物活性和以微生物为媒介的有机质矿化作用,改变土壤元素的生物地球化学循环过程,从而对土壤生态系统结构和功能产生影响。冻融作用对土壤理化性质的作用主要受冻融速率、温度、冻融交替次数和土壤含水量、pH值、有机质、土壤质地状况等因素的影响。通过冻融作用改善土壤结构,提高土壤微生物活性和养分的有效性,有利于耕作和促进植物生长,但也可通过含水量的重新分布和径流淋失而导致土壤养分损失。 相似文献
20.
艾比湖地区冻融作用对梭梭群落土壤酶活性及微生物数量的影响 总被引：3，自引：0，他引：3
冻融作用对酶和微生物活性具有重要影响,进而影响植物群落的生长发育。为深入了解荒漠优势种梭梭群落冬季土壤生态过程,于2012年10月~2013年10月,对土壤冻融期、冻结期、融冻期和生长季的艾比湖典型样地进行野外实地观测、采样和室内分析。通过对比分析不同冻融阶段土壤含水量、pH值、有机质、全氮、酶活性和微生物数量的变化特征。结果表明:(1)土壤含水量,融冻期 >冻结期 >冻融期 >生长季,土壤pH值,生长季 >融冻期 >冻融期 >冻结期,各土层土壤含水量以浅层土表现最为显著(P <0.05),不同冻融阶段各土层pH值差异性较大,冻融期、冻结期和生长季表层土壤pH值较大,融冻期浅层土壤pH值较大。(2)土壤有机质和全氮含量的波动状况相似,分别在融冻期和生长季呈现波峰和波谷,不同土层间全氮和有机质含量差异性较小,以冻融期和生长季表现最为显著(P <0.05)。(3)土壤酶活性的变化中,过氧化氢酶、脲酶和蛋白酶在融冻期含量最大,冻融期次之,蔗糖酶在冻结期活性最大,土壤微生物数量的变化以融冻期最大,除此之外,各冻融阶段细菌和放线菌占主导,真菌含量相对较少。(4)冻融循环次数分布于冻融期和融冻期,对土壤酶活性和微生物数量具有一定的影响,致使融冻期土壤各因子大于冻融期。 相似文献