新疆西域砾岩抗剪强度现场直剪试验研究

西域砾岩物质成分复杂、胶结差、强度低、易风化。为了研究西域砾岩的力学特性,为天山经济带内相关工程的开发建设与地质环境防灾减灾提供支撑,本文以奎屯河右岸山前西域砾岩为研究对象,开展现场直剪试验,根据试验结果可得：西域砾岩抗剪强度参数内摩擦角范围值在25.2°～37.3°,粘聚力0.48～1.45 MPa;西域砾岩抗剪强度由砾石颗粒间的摩擦力以及由胶结物和水膜的分子引力所产生的粘聚力共同组成,西域砾岩高程越低埋深越大,胶结程度越好,粘聚力越高;西域砾岩直剪破坏的破坏面呈凹陷状,起伏差为±4 cm,破坏为颗粒间绕粒破坏,基本无巨粒颗粒的剪断。     

原状黄土冻融过程抗剪强度劣化机理试验分析

通过对西安Q₃原状黄土在封闭系统冻融作用下的电镜扫描和直剪试验,研究了冻融作用对原状黄土微观结构和强度的影响。试验表明：冻融过程中原状黄土微观结构发生显著变化,大颗粒集粒数量明显减少,小粒径土颗粒所占比重增加,孔隙面积比增加。进一步基于损伤力学理论,得到微观结构冻融损伤度随冻融次数增加呈指数增加趋势,反映出冻融作用一定程度上破坏黄土体的结构强度,但多次冻融后黄土体结构强度趋于稳定的残余强度。冻融过程土样表面结构发生破坏,且含水率越高,土体表面特征破坏越严重。粘聚力随冻融次数增加呈指数衰减趋势,且含水率越高,粘聚力衰减幅值和速率越小;粘聚力随含水率增加表现出线性衰减特征,且冻融后粘聚力与含水率的变化规律近似重合;内摩擦角无明显规律性变化。粘聚强度冻融损伤系数随冻融次数增加呈指数增加趋势,随含水率升高有增大趋势。基于试验数据规律性,进一步提出了原状黄土粘聚强度劣化模型,该模型经试验验证可较好描述原状黄土粘聚强度劣化规律。     

含水率和颗粒级配对稍密碎石土抗剪性能及地基承载力的影响

碎石土因特殊的工程特性而被科研人员关注,但对大粒径、粉质粘土填充、稍密状态下碎石土的力学性能涉足较少。根据该类型碎石土特点及大量勘察结果配置出两种比较典型级配的稍密碎石土,通过大型直剪试验仪测定了不同含水率状态下碎石土试样的抗剪强度,绘制剪应力与水平位移的关系图,通过一元回归得出稍密碎石的抗剪强度指标c、φ值,分析了不同含水率、不同级配对稍密碎石土抗剪性能的影响。结果表明：随着含水率的增大,碎石土粘聚力总体呈减小趋势,但变化趋势具有显著的阶段性且和粉质粘土的含量有关,含水率变化对碎石土内摩擦角的影响较小。用规范推荐方法计算了该类型碎石土地基承载力,并与地方规范经验取值和勘察工程实践取值进行了对比,结果表明：含水率对地基承载力影响较大,且与碎石土填充物的粉质粘土含量有关,粉质粘土含量越高,承载力影响越大。     

土体抗剪强度指标变异水平对边坡稳定安全系数取值的影响

针对传统的边坡稳定极限平衡方法不能考虑土体抗剪强度指标变异性影响的问题,基于极限状态的概率分析原理,采用Monte-Carlo法对均质路堤边坡的稳定性开展了可靠度计算,讨论了稳定安全系数一定的条件下边坡失效概率随土体抗剪强度指标变异水平的变化规律,分析了安全系数与边坡可靠指标的对应关系及其随土体抗剪强度指标变异水平的变化特征。研究表明：边坡可靠度受土体抗剪强度指标变异性影响显著,呈现出随土体抗剪强度指标变异水平提高而急剧减小的趋势;为保证边坡具有相同的可靠性,安全系数的取值应与土体抗剪强度指标的变异性相适应,据此提出了基于可靠指标和土体抗剪强度指标变异水平的安全系数取值原则及其对应的三参数函数关系式。     

不同加载方式SIP墙体的抗剪性能

以3种不同的单向加载方式对以木质OSB覆面的SIP墙体进行侧向加载实验,对比分析3种加载方式下SIP墙体的破坏形式及这3种加载方式对墙体抗剪性能参数的影响,结果表明:3种加载方式得到的墙体的抗剪性能指标有所差异,其中,采用ISO22452加载协议,即对墙体施加持续增加载荷的加载方式所得到的极限承载力最大、极限位移和延性系数居中,分别为46.06 kN、71.83 mm、3.31;采用ASTM E72-05加载时极限承载力居中、极限位移及延性系数最大,分别为:40.66 kN、76.97 mm、4.07。采用ASTM E564-06加载,即对墙体施加阶段载荷并使阶段目标载荷持续作用一段时间的方式,所得到的极限承载力、极限位移及延性系数最小,分别为37.73 kN、54.92 mm、2.91;3种加载方式对墙体破坏形式的影响不大。     

茶树机剪机采试验示范总结

为推动我县茶叶机械化生产,提高茶叶采摘质量,降低成本,提高工效,在农业部农机化司的大力支持下,我局年初从浙江引进落合、川崎两个厂家生产的修剪机106台、采茶机84台,在走马镇进行了茶树机剪机采试验示范,取得了较好的效果,深受当地茶农的欢迎,为全县大面积推广茶树机剪机采积累了一定的经验。1基本情况1.1机剪机采面积本次试验示范在白果民族茶厂木耳山茶园基地和世为公司红罗沟茶园基地进行,面积共266.7hm2。1.2茶叶产量266.7hm2机采示范茶园的鲜叶总产量为2400t,平均亩产干茶150kg,比非机采茶园对照平均亩产100kg增产33%。增产主要原因…     

污水环境对水泥土力学性能的影响试验研究

由于多数地下水泥土工程直接与地下腐蚀性介质环境接触,必将导致水泥土材料的逐步劣化甚至失效破坏。以某市区工地附近明渠排放的污水作为侵蚀性介质,制作了不同水泥掺量的水泥土试件,通过对比试验,研究了污水环境和清水环境下不同水泥掺量、不同龄期的水泥土抗压强度和抗剪强度。结果表明,在污水或清水环境下,相同水泥掺量水泥土30 d龄期的抗压强度几乎相等,随着龄期的增加其抗压强度均逐步增大,但污水环境下其抗压强度增长的幅度明显小于清水环境,90 d后清水环境的水泥土抗压强度不再增长,而污水环境的抗压强度开始降低;污水环境和清水环境下的水泥土内摩擦角和黏聚力随龄期、水泥掺量的增加均逐步增大,污水环境下龄期90 d后的内摩擦角和黏聚力均开始降低。     

水稻混栽抗稻瘟病试验初报

稻瘟病是平塘县水稻生产的主要病害之一 ,为筛选一种简单易行 ,长期稳定 ,经济实惠 ,安全有效的稻瘟病防治方法。 2 0 0 2年选用生育期相近的主推水稻品种 ,按不同比例进行混栽 ,摸索其对稻瘟病发病情况以及产量的影响。1　材料与方法1.1　试验田基本情况试验田位于平塘县白龙京舟坝 ,户主交懂村罗太兵 ,海拔 780m ,前作油菜 ,肥力中等 ,属沙泥田 ,排灌方便。1.2　参试品种及来源协优 6 3,平塘县种子公司提供 ;金优 6 3,黔南州种子公司提供 ;K优 5号 ,平塘县种子公司提供。1.3　试验设计设协优 6 3、金优 6 3和K优 5号各净栽一小区为对照 ,…     

固化疏浚淤泥作路基材料工程特性试验研究

为了探讨粉煤灰和工业矿粉固化疏浚淤泥作路基材料的可行性,通过一系列室内实验研究了不同固化剂配比对固化淤泥击实特性、水稳定性、承载力和抗剪强度的影响。实验结果表明,不同固化剂配比下固化淤泥的最大干密度均超过1.50 g/cm³,最优含水率约为20~21%;淤泥固化处理后浸水4 d的膨胀率均不超过1.1%,水稳性大幅提升;矿粉含量越高,粉煤灰含量越低,CBR（California Bearing Ratio）值越高,土样的承载力越高,抗剪强度也越高。不同工况浸水4 d的CBR值均达到了较高的水平,工况SD10FA20MP（淤泥：粉煤灰：矿粉=7：1：2）CBR值最高,达到了34.8%,是规范中高速、一级公路路基填料要求最低CBR值的4.35倍,作路基填料使用可行。     

派酶-土壤-黑麦草根系复合体抗剪强度试验研究

摘要: 提出一种派酶-土壤-黑麦草根系复合体,即在含派酶土壤中加入黑麦草根系。探讨了不同含酶量及含根量下复合体的抗剪强度,并在具有不同含酶量的土壤中种植黑麦草种子。由试验结果可知：黑麦草种子可以在含派酶土壤中存活并生长;在考察范围内,复合体的抗剪强度随含酶量的增加而增大,φ值随含酶量的Jiao Xin增加先增大后减小。     

Analysis of the Effect of Filling Soil Moisture Content to the Gravity Retaining Wall’s Performance

The moisture content of filling has a major impact on the soil shear strength parameters, which thereby affects the calculation of earth pressure and then influences the stability of the retaining walls. This article studies on the basis of the previous studies, which is about the influence of the moisture content to shear strength parameters of the unsaturated filling. By having shear tests of soil samples with ZJ type direct shear apparatus and combining with relevant knowledge of the strength theory, shear strength parameters C and φ are obtained. Then the experimental results are given numerical simulations to determine the influence coefficients of the affect of moisture content to C and φ, and are used to get the relation formulas of moisture-cohesion, moisture content-internal friction angle with good goodness of fit.When soil samples are given the pressure experiments by using universal testing machine,the soil particle size distribution and the density of filling are basically consistent, and only change the moisture content of filling to study the influence of fillings of different moisture contents to the performance of retaining walls. In the experiments, it can be found that with the pressure increasing, the compressibility and the moisture content of the filling show a nonlinear relationship. At first the compressibility increases with the increases of moisture content , and then decreases when the moisture content reaches a certain value. By the end of the experimn, according to Rankine's earth pressure theory , the earth pressures of retaining walls are calculated corresponding to a variety of filling state, and the relation formulas of the moisture content-active earth pressure, moisture content-passive earth pressure are getting by the use of numerical simulations to the results.     

Experimental Analysis on Shear Strength Characteristics of Sand-Gravel Mixtures

The effect of gravel content and shape on shear strength of sand-gravel mixtures was investigated through a series of direct shear tests under different stress states (σ = 50,100,150 and 200 kPa) in laboratory. Mixtures were made up of sand with rounded and angular gravels, respectively. The gavel contents of 20%, 40%, 60% and 80% were used in sample preparation. The results indicate that the dilatancy and shear strength of sand-gravel mixture increase with increasing gravel content and irregular degree of gravel shape. The gravel content has a more visible effect on the shear strength rather than that of the gavel shape. The minimum void ratio of the mixture is a characteristic parameter to investigate the relationship between gravel content & shape and the shear strength of sand-gravel mixture.     

Experiment Study on Soil Properties of Shennv Stream Landslide in Wu Gorge

Accurate obtainting soil parameters of landslide is the key links for landslide stability evaluation and project management . This article takes Shennv Stream landslide in Chongqing Wushan County as an example, implementing unconsolidated and undrained shear test and mineral composition analysis by X ray diffraction for soil in different elevations of landslide ,conducting sensitivity test for various soil parameters of reservoir landslide change with different water level.Study shows that : Mineral composition of soil mainly contains Calcite, Quartz and clay mineral. Hydrophilic minerals in clay mineral have great effect on stability of landslide. Shear strength decreases by influence of water content on cohesion. Cohesion decreases sharply in a quadratic function relation with water content increasing .When water content comes to 18.21% ,change of cohesion tends to be stable.But the internal friction angle of landslide soil decreases linearly in small amplitude with an increase of water content. Research results may provide some important references for rationally choosing strength parameters of soil in similar landslide.     

Experimental Research on Municipal Solid Waste Landfill''s Strength Character in a Refuse Dump of Chongqing

With the development of economic and society,more and more waste landfill gradually threaten to the development of the city.Some special tests are done to study the relationship of the Municipal solid waste(MSW) strength and the stability of MSW landfill structure.A geo-technical test with the soil samples collected at the scene is done in the laboratory through direct sheared device and the thri-axial sheared device,the disciplinarian and factors are analyzed.The results are referenced to the design and construction of new-built MSW and finished rubbish field.It is shown that some parameters such as composition,particle magnitude,water content,compressing method,intensity and time,will greatly affect the strength character of MSW.     

Experimental Analysis of the Water Weaken Effect on Gravel Soil Roadbed Locating in the Reservoir Region with Different Compactedness

It is vital to get the accurate data of the shear strength parameters of gravel soil with different water content and compactedness before they conduct the stability analysis for gravel soil roadbed. Under several test conditions, a series of direct shear tests were performed by using some gravel soil samples obtained from a selected roadbed which is under the influence of water level fluctuation. The corresponding results show that the gravel soil cohesion increased as the water content of fine soil increases till it meets its peak value, then it will decrease as the water content keeps increase. However, the internal friction angle will decrease slowly with the increase of water content of fine soil in the initial phase, and then it will decrease rapidly as the water content keeps increase. And on the other hand, the fitted shear strength parameters calculated from the test data has been influenced by the pre-load values that used to prepare soil samples, especially for the condition that the pre-load value less than the normal stress value applied in the direct shear test. All in all, the fitted shear parameters will be controlled by the relationship among water content, pre-load value and normal stress.     

Experimental Study on Shear Strength of High Strength Concrete Columns

On basis of the experiment on sixteen high strength concrete columns, their shear behaviors are analysed. The effects of shear-span ratio and axial compression ratio on failure behavior, cracking shear and shear strength are analysed. The authors have discussed the suitability of the design equations for shear strength in the code. This experimental study on shear strength of high strength concrete frame columns is the first one in this field at home and the results can be served as reference for the code of high strength concrete design.     

Experiments on influence of slurry kinds on mechanicalbehavior of interface between gravel and concrete

The mechanical behavior and mechanism of the interface between structure and coarse grained soil are investigated through simple shear tests on the conditions of bentonite slurry, clay slurry and without slurry, respectively. The results indicate that different kinds of slurry have important influence on shear strength. Compared with the interface without slurry, the shear strength with bentonite slurry reduces by 45% approximately, significantly more than clay slurry which reduces by 10%. The value of the friction angle with bentonite slurry is about 60% of that with clay slurry. Shear displacement increases as upright stress increases when reaches its failure states at the same height, and shear displacement with bentonite slurry is smaller than that with clay slurry when with the same upright stress and height. The upright displacement with bentonite slurry is greater than that with clay slurry under the same upright stress. In addition, shear dilatation is apparent under the low normal stress when without slurry. Otherwise, it appears as shear contraction.