水泥稳定三峡库区风化砂回弹模量试验及模型评估

以水泥稳定三峡库区风化砂的回弹模量值为研究对象,在风化砂中分别掺入3%、5%、7%、9%的水泥制作试样,然后各自养护7、14、21、28、35、56、70 d,开展室内回弹模量试验。试验结果表明:掺水泥能显著提高风化砂的回弹模量值。在相同的养护龄期下,随着水泥掺量的增加,回弹模量值逐渐增大,增长的幅度先大后小,二者呈现良好的对数函数关系;在相同的水泥掺量下,随着养护龄期的增长,回弹模量值也逐渐呈线性增大,且在最初养护的28 d内,回弹模量值的增长占整个测试期内的95%左右。通过回归分析,分别建立了水泥掺量与回弹模量值之间、养护龄期与回弹模量值之间的数学模型,再通过补充试验,进一步验证了所建数学模型的正确性及精确度。     

未水化水泥颗粒后期水化对UHPC性能的影响

采用高温加速试验,并结合烧失量法、力学试验、测长法、电通量法、碳化等手段研究了不同养护温度和水胶比条件下未水化水泥颗粒后期水化对UHPC性能的影响。结果表明：60 ℃水养护能够有效加速UHPC中未水化水泥颗粒的后期水化,试块的结合水量在90 d内趋于稳定。随养护龄期的增长,UHPC试块先收缩后膨胀,90 d的抗折强度、抗氯离子渗透性和抗碳化性能均下降,抗压强度尚无明显损失。水胶比越低,UHPC试块90 d的结合水量增长率越大,膨胀值越大,抗折强度损失率也越高。     

早龄期加载对粉煤灰混凝土变形及强度的影响

研究了粉煤灰掺量、加载龄期和加载应力对粉煤灰混凝土早期变形及加载后强度变化的影响。研究结果表明：随着粉煤灰掺量增加,混凝土的变形量逐渐降低,当掺量为30%时,变形量减少了33.6%;随着加载龄期提前或加载应力增大,粉煤灰混凝土的早期变形量增大,其中,加载应力的影响尤其明显,60%加载应力（60%的标准养护条件下7 d轴心抗压强度）比20%加载应力下混凝土最终变形量增加了277.2%;混凝土初始加载时间提前或加载应力增大会导致加载后粉煤灰混凝土强度下降,加载应力比加载龄期对加载后粉煤灰混凝土强度的影响更明显。     

异位发酵床垫料的直剪切及压缩试验研究

为研究不同含水率的条件下异位发酵床垫料:抗剪强度、黏聚力、内摩擦系数、压缩载荷的变化规律.本研究采用土壤力学试验方法,测定垫料五种不同含水率的相关参数.结果表明:当垫料含水率为29.22％～36.13％时,抗剪强度、内摩擦角系数会随着含水率的增大而增大;当含水率为45.55％～61.11％时,抗剪强度、内摩擦角系数会随...     

粉煤灰水泥浆体的电阻率与化学收缩及自收缩的相互关系

为研究粉煤灰的硅酸盐水泥浆体的电阻率、化学收缩及自收缩的变化规律,定量描述水泥基材水化过程中自收缩和未充水毛细孔体积在化学收缩中所占的比例变化,测定了不同水胶比和粉煤灰掺量的早龄期水泥基浆体的电阻率、化学收缩和自收缩。结果表明：水泥基浆体在硬化减速期的电阻率随时间对数的曲线斜率K和浆体3 d抗压强度成线性关系,并进一步论证了K值对水泥浆体结构密实速度的物理意义及其推测强度的应用价值;浆体的化学收缩和自收缩分别随水胶比升高或粉煤灰掺量增大而降低。浆体在24 h后的单位体积化学收缩和30 h后的自收缩随电阻率的发展均表现出线性关系。定量地提出了终凝后自收缩变化量与终凝后线性化学收缩变化量的比例参数γ的概念,较小的γ值表明：与未充水毛细孔相比,自收缩的比例很小;同一样品的比例参数γ表现出随水化时间逐渐减小。     

大豆内摩擦角的测定与实验研究

利用剪切仪,测定了在不同的剪切速度、不同的法向压应力、不同的水分条件下大豆的内摩擦角。结果表明:随着剪切速率的增大(1.33～4.33 mm/min)大豆内摩擦角减小,随着法向压应力的增大(0.25×105～1.00×105Pa)大豆内摩擦角减小,随着水分含量的增大(12.11%～18.02%)大豆内摩擦角先增大后减小。     

含水率对糙米内摩擦角影响的实验研究

利用土工合成材料综合测定仪,以江苏盐城产糙米为样品,测定了在不同法向压应力和不同含水率的条件下,糙米的剪切应力并计算出内摩擦角。实验结果表明:在剪切速率不变时,糙米的内摩擦角通常会随着法向压应力的增大而逐渐减小;当法向压应力较小(25kPa)时,糙米的内摩擦角会随着含水率的增加而逐渐增大。当法向压应力较高(75kPa～100kPa)时,随着含水率的增加,糙米的内摩擦角逐渐增大,达到某一峰值后,随着含水率的继续增加而逐渐降低。     

Stability analysis on shallow tunnel with floor lift under inclined ground by upper bound method

采用极限分析上限法,基于内外能耗守恒原理,通过构建考虑隧底隆起的斜坡地段浅埋隧道破坏模式,推导出围岩压力的计算式,并通过典型算例重点分析了典型因素对隧道围岩稳定性的影响。研究结果表明：基于泰沙基极限平衡法进行隧道围岩支护设计较为保守,不考虑隧底隆起的极限分析方法次之考虑隧底隆起极限分析方法的风险最大;斜坡地表倾角增大对浅埋隧道稳定性有着不可忽视的不利影响;围岩压力随岩土侧压力系数减小、埋深增大、断面尺寸加大而增大;岩土黏聚力增大、内摩擦角增大对提高浅埋隧道围岩稳定性有积极作用。     

直剪法用于糙米内摩擦角的测定与研究

利用土工合成材料综合测定仪（直剪仪）,以水分含量14.57%的糙米为样品,测定了在不同的法向压应力、不同的剪切速率下糙米的剪切应力并计算出内摩擦角。实验结果表明：糙米的剪切应力随着法向压应力（25kPa～100kPa）的增大而增大;剪切速率（1.33mm/min～2.67mm/min）较低时糙米的内摩擦角随着法向压应力的增大而减小;随着剪切速率（1.33mm/min～5.20mm/min）的增大,糙米的内摩擦角减小。     

非线性Mohr-Coulomb破坏准则下边坡可靠度上限

传统边坡可靠度分析往往在岩土参数服从线性Mohr-Coulomb（简称线性M-C）破坏准则的假设条件下进行,并且常常采用极限平衡法或有限元法计算安全系数。然而,岩土介质破坏准则具有一定的非线性。为能更加实际地描述岩土破坏机理和得到严格精确的解,基于非线性Mohr-Coulomb（简称非线性M-C）破坏准则,结合极限分析上限法和蒙特卡洛法,进行边坡可靠度上限分析。当非线性参数m=1时,与等效的线性M-C破坏准则进行对比计算,验证了方法的可行性。同时,将初始粘聚力、内摩擦角arctan（c₀/σ_t）和非线性参数作为随机变量且服从截断正态分布,进行了参数变异性和敏感性影响分析。研究表明：非线性M-C破坏准则下,边坡可靠度随初始粘聚力、内摩擦角arctan（c₀/σ_t）和非线性参数变异性的增大而减小;边坡可靠度随初始粘聚力和内摩擦角arctan（c₀/σ_t）的增大而增大,随非线性参数的增大而减小。     

Influence of Ca(OH)2 on Strength of Low Proportional Cemented Soil

Laboratory experimental research is performed by strengthing three different types of soil with low proportional cement to test the unconfined compressive strength of such cemented soil under different dosages of Ca(OH)2 and the different ages. The variation rules and causes of the unconfined compressive strength of these three types of age-different cemented soil with increasing the dosage of Ca(OH)2 are analyzed. The results shows that the intensity of red clay cement improves most obviously with Ca(OH)2 content increased, followed by silty clay, and sand is the weakest. The reason is that the fineness of the soil affect the strength of the cement greatly. The finer the soil, the more clay minerals in soil. The increase in Ca(OH)2 content promotes the ion exchange and the occurrence of volcanic ash, which improves the strength of cemented soil. Among the three types of soil in this experiment, the fineness of red clay particles is the best, so the intensity of red clay cement improves most obviously with Ca(OH)2 content increased.     

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 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.     

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。     

Dynamic Influence of Sustained Small Rainfall Infiltration on Stability of Unsaturated Soil Slope

Taking the moisture content as main control parameter of shear strength of the soil, we analyze the variational properties of moisture content and shear strength with the change of rainfall time during the small sustained rainfall infiltration, and establish the relationships between total cohesion as well as effective angle of friction and the time of sustained small rainfall infiltration into an unsaturated slope. With the rainfall infiltration, the influence area of slope expands. Through the strength reduction method based on FLAC3D, the dynamic safety factor of slope in different time and the duration time before the failure of the slope are obtained. The results show that the slope critical sliding surface is yet unsaturated during a sustained small rainfall.     

Preparation of the supplementary cementitious material offerronickel submerged arc furnace slag and its properties

The ferronickel submerged arc furnace slags are stored up more and more, as a result, seriously influenced the sustainable development of the nickel industry. By grinding, the ferronickel submerged arc furnace slag is mechanically activated, then can be used as supplementary cementitious material, thus a comprehensive utilization way of ferronickel submerged arc furnace slag is developed. Using such processed slag to replace cement from 10% to 40% in mass, with the increase of replacing dosage, the water demand of standard consistency of cement paste is lowered, the fluidity of mortar is raised; the compressive strength of mortar is decreased; the flexural strength is increased followed by a decrease after the dosage is above 10%, the ratio of flexural strength to compressive strength is increased. The experimental results indicate that the ferronickel submerged arc furnace slag can be used as supplementary cementitious material and has an increase of flexural strength and effect of plasticizing and water reducing.     

Cementation Effect with Cement during Cold In Place Recycling System of Asphalt Pavement

Different kinds of structures of RAP and different contents of cement were prepared. By means of standard compaction test, unconfined compressive strength, water stability, modulus and SEM test, the cementation effect with cement was studied. It was shown that the maximum dry density of RAP mixture rose from 1.91g/cm3 to 2.00g/cm3 with the increase of cement content when A/S was 0.4. The maximum dry density of RAP mixture would rise when adding more asphalt. The unconfined compressive strength rose from 1.48MPa to 2.63 MPa and then down to 2.28MPa when cement content was 6%. The best property could be got when A/S was 0.4 and the cement content was 6% with 9.5% water. The compressive strength of RAP mixture declined after it was cured in water for 24 h, but it had the same tendency with those of which had not been maintained in water. And it is also found that RAP does not obtain better stabilities in high temperature with modular test. From SEM test, it is shown that ettringite and C S H interlace and form the netted structure, and the aggregate would be enwrapped to increase the strength.     

Experimental Investigation of Stabilized Soft Soil by New GSC

Soft clay is stabilized by desulphurization gypsum and steel slag-slag blended cementitious materials (GSC), which can not only reuse industrial waste and decrease second pollution, but also can conserve mineral resources and protect natural ecology. The variation of unconfined compressive strength of the clay improved by GSC with different mixing ratios and water-GSC ratio and ages was studied through the laboratory experiments. The long-term strength of stabilized soil is predicted with GSC by quasi-water-GSC ratio. The results show that the more the mixing ratios is, the better the stabilized effect of soft soil is. With increase of curing period, the strength increasing of GSC-soil is consistent with cement-soil, and it has lower strength in the early stage. When mixing ratios of GSC is more than those of cement by 3%, if the water-GSC ratio is less than those of cement, it has the higher strength than cement-soil, after 28 days. The results show that GSC stabilized soil is feasible and it can meet the demand of cure strength.     

Effects of Cement Additives on Properties of CSA Cement from MSWI

Municipal solid waste incineration fly ash (MSWI) was successfully used as raw material in sintering and preparing a calcium sulphoaluminate (CSA) cement clinker in laboratory. The effects of different types and different addition percentages of cement additives on compressive strength and hydration properties were investigated. The results showed that lime (LI) powder / slag (SL) powder was compatible in CSA cement system while the activities of fly ash(FA)/ MSWI was low. Adding these four types of cement additives in CSA cement system respectively, there were negative effects on compressive strengths of hardened cement at early age while LI/SL improved the compressive strength at later age. The performance of combined additives was better, especially, the specimens with 10%LI+10%SL, 10%LI+10%MSWI, and 5%LI+15%SL.