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通过滑坡防治格构锚固大型物理模型试验,分析了土质滑坡格构锚杆体系在坡顶荷载下的变形和位移,揭示了格构锚杆的抗滑机制,探讨了锚固力与坡体位移及锚杆变形的关系,提出了极限锚固力的计算方法。结果表明：滑坡滑动时,格构梁与坡体整体发生旋转滑移,锚杆在滑面处发生了弯曲变形,处于弯曲和轴向拉伸组合变形状态;格构锚杆的抗滑作用表现为锚杆在滑面处的抗剪抗滑和锚杆格构梁的挡土阻滑;格构锚杆的极限锚固力由初始预应力、锚杆弯曲变形引起锚拉力、坡体位移引起锚拉力三部分组成,可通过公式 计算。该研究结果可为格构锚固体系的优化设计提供一定的参考。 相似文献
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提出锚杆锚固力可分为托锚力，剪锚力和挤胀力三部分的新概念及其含义，分析了锚杆拉拔试验得到的拉拔力与锚固力的关系，认为最大拉拔力不是锚杆锚固力，而是锚杆可能达到了大托锚力，分析了单根锚杆的三种破坏形式。 相似文献
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为了研究爆破掘进施工对巷道支护锚杆的影响,采用结构动力学理论,从理论上推导出了锚杆在爆破地震波作用下的振动规律,计算出锚杆上的位移、振速、轴力随时间的变化,研究了黏结式锚杆在爆破动荷载作用下的动力响应特征。结果表明：自由段锚杆的轴力和轴向振速呈现指数型衰减,而锚固段锚杆的轴力和轴向振速以及剪应力呈现正弦变化,整体表现为先增大后减小。锚固长度对锚杆振动效应影响较大,不同锚固长度时锚杆受力状态不同,在锚杆满足抗拉强度的前提下,可以适当减小锚固段长度。剪切刚度对锚杆的振动有一定的影响,剪切刚度越大,锚杆与锚固砂浆之间的剪应力也越大。故为了防止锚杆不发生剪切破坏,尽量选择剪切刚度较小的锚固剂材料。研究成果对掘进爆破安全技术的提高具有一定的指导意义。 相似文献
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上层水泥浆预应力锚杆广泛应用于上层基础加固。锚杆头部主要作用是将拉杆的力传递给建筑物，易于掌握。水泥浆团结体对拉杆的握裹力大小取决于水泥浆质量及拉杆表面的清洁程度与凸凹程度。此类传力方式锚杆没有充分发挥钢筋拉杆的应力，造成锚固段深部上层抗剪应力的浪费，减小锚杆抗拔力。倒拉式锚杆则克服了上述缺点。水泥浆团结体与上层间的作用力对锚杆的极限抗拔力起决定作用，它的大小决定于水泥浆团结体凸体对上层的剪切应力和相对平滑的水泥浆团结体对土层的摩擦阻力。土层蠕变作用限定了锚杆安全系数的取值范围。锚固段要求设置在非重力土楔范围以外的稳定区域。 相似文献
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《岩土力学》2020,(1)
为了研究爆破掘进施工对巷道支护锚杆的影响,本文采用结构动力学理论,从理论上推导出了锚杆在动荷载作用下的运动规律,计算出锚杆上的位移、振速、轴力;分析研究了黏结式锚杆在爆破动荷载作用下的动力响应特征。结果表明:自由段锚杆的轴力和轴向振速呈现指数型衰减,而锚固段锚杆的轴力和轴向振速以及剪应力呈现正弦变化,整体表现为先增大后减小。锚固长度对锚杆振动效应影响较大,不同锚固长度时锚杆受力状态不同,在锚杆满足抗拉强度的前提下,可以适当减小锚固段长度。剪切刚度对锚杆的振动有一定的影响,剪切刚度越大,锚杆与锚固砂浆之间的剪应力也越大。故为了防止锚杆不发生剪切破坏,尽量选择剪切刚度较小的锚固剂材料。研究成果对掘进爆破安全技术的提高具有一定的指导意义。 相似文献
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为揭示GFRP锚杆在土遗址加固中的性能,进而克服现有竹、木、复合锚杆锚固的局限性,拓展该新型材料在古遗址加固中的应用,选择直径22mm和25mm的GFRP锚杆开展了现场锚固测试试验。通过单级和循环两种加载模式,获取了两种杆体的破坏模式与极限锚固力; 在杆体砂浆界面布设应变片,获取了受荷过程中界面监测点剪应变的变化特征与分布规律。结果表明:两种锚固系统均失效于砂浆土体界面,22mm GFRP杆体极限锚固力50kN,而25mm GFRP杆体超过120kN; 从加载端到末端监测界面剪应变呈衰减分布,在较大荷载下由于加载方向与杆体轴向微弱偏离导致局部出现受压现象,试验过程中监测界面未出现脱黏现象。研究表明GFRP锚杆可以部分替代复合锚杆,在土遗址载体加固中具有良好的应用前景。 相似文献
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对大松动圈围岩巷道,单一锚杆支护难以实现对整个破裂区围岩的锚固控制,采用锚网索联合支护时,应考虑锚杆支护对联合支护设计的作用。通过分析大松动圈围岩锚杆锚固支护机制,提出量化锚杆支护作用的锚固承载系数,形成锚网索联合支护参数量化计算方法。研究结果表明：锚杆锚固支护后将大松动圈围岩分为浅层锚固区和深层破裂区,浅层锚固区具有一定承载能力,可视作锚索的等效托盘;在锚网索联合支护中,浅层锚固区承载结构稳定的条件是锚固结构承载力大于环向轴力且能够有效控制破裂区围岩;锚固承载系数大小主要取决于浅层锚固区与破裂区和锚杆预紧力与设计锚固力的关系,对于大松动圈围岩其取值范围为0.45～0.75。经现场试验可知,巷道顶底板移近量为273 mm,两帮移近量为393 mm,表面位移曲线趋于平稳,采用该方法得到的锚网索支护参数有效保证了巷道的正常使用。 相似文献
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采用室内加速腐蚀试验方法,研究了砂浆受腐蚀后砂浆锚杆锚固体的锚固特性变化情况。通过对不同腐蚀阶段砂浆锚杆锚固体中锚杆-砂浆界面以及砂浆-基体界面的黏结强度及荷载-位移关系的测试及分析,得到了界面黏结特性随砂浆腐蚀时间的变化关系。结果表明：随着砂浆受腐蚀程度的增加,锚杆-砂浆-基体三者界面间的黏结强度均呈线性下降,锚杆-砂浆界面间剪切刚度随着腐蚀时间的增加而减小,而砂浆-基体界面间的剪切刚度受砂浆腐蚀程度的影响不大,但界面间的化学胶着力会随砂浆腐蚀程度的增加而降低。 相似文献
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为研究水泥砂浆固化土剪切强度特性和合理确定水泥砂浆固化土工程应用的配比,从掺砂量、水泥掺入比、原料土含水率及砂料粒径入手,对水泥砂浆固化土进行了室内固结不排水三轴（CU）试验研究。结果表明,掺砂可以改善固化土强度;随掺砂量的增加,黏聚力和有效黏聚力先增加后减小,转折点的掺砂量为最佳掺砂量（10%左右）,内摩擦角和有效内摩擦角不断增加,一定掺砂量下增加水泥掺入比可有效地提高固化土的强度;随着含水率的增加,固化土的黏聚力呈近似线性减小的关系,而内摩擦角几乎保持不变,采用水泥砂浆处理高含水率软弱地基时适当提高掺砂量,可以较大幅度改善固化土的力学性质;在掺料配比一定的情况下砂料粒径对固化土的抗剪强度指标存在一定的影响。采用单一粒径砂料的固化土抗剪强度更高,该单一粒径在固化土级配良好的前提下,不均匀系数Cu趋于最大、曲率系数Cc趋于最小 相似文献
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The residual shear strength of soils is increasingly becoming an active research area, as landslides occur almost daily all over the world. Since Skempton published his landmark paper in 1964, several researchers proposed correlations between soil index properties and residual friction angle of soils for preliminary estimates. However, recent data gathered from Japanese colluvium soils indicate that previously proposed charts correlating soil index properties with residual friction angle yield very poor estimates. In this study, first previously published Japanese data are reevaluated to establish a theoretical foundation for such correlations. Then, it is shown that equivalent smectite content (ESC) largely controls the residual friction angle of soils. In the second stage of the paper using the data of several researchers, it is shown that there is piecewise linear correlation between the equivalent basal spacing (EBS) and the residual friction angle. This study lays down a foundation for theoretical correlation between EBS and residual friction angle of soils. 相似文献
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Architectural mortar from two ancestral Pueblo sites (Spruce Tree House and Nordenskiöld's Ruin 12) located in Mesa Verde National Park was investigated using visual, mineralogical, and geochemical techniques. Results indicate ancestral Pueblo people had a preference for mortars composed of sand and clay contents that produce a USDA textural class of sandy clay loam to clay loam. A temporal trajectory of soil selection is observed at Spruce Tree House, with mesa‐top soils being preferred during the early period of occupation, but with soils below cliff dwellings preferred during later periods. Mortar geochemical composition is found to differ between cliff dwellings, and sometimes between households within a cliff dwelling, due to local soil differences and/or potential amendment additions. Results from Spruce Tree House indicate that contemporaneous households shared access to mortar sources. The prevalence and possible origins of gypsum found in mortar are discussed. Finally, this research examines the possibility that land tenure rights may have extended beyond those lands used exclusively for agricultural purposes. © 2011 Wiley Periodicals, Inc. 相似文献
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If the free vertical movement of the upper rigid part of the shear box is hindered during shearing, a frictional force is mobilized between the specimen and the vertical walls of the shear box. This causes either unloading (for contractant soils) or additional loading (for dilatant soils) of the specimen during shearing. If no correction of the applied vertical load with respect to the wall friction is taken into account, the resulting shear strength can be either underestimated (for contractant soils) or overestimated (for dilatant soils). For example, in a particular investigation of a normally consolidated soil, the measured friction angle from a direct shear test was almost 8° smaller than the angle from a triaxial test. This paper, therefore, presents a method for direct measurement of the frictional force at the contact between the vertical walls of the box and a fine-grained soil. If the wall friction is taken into account, the friction angle from the shear box coincides well with the angle from triaxial tests. If the wall friction cannot be measured during the test, a sufficiently large vertical gap should be adjusted in case of soft soils, in order to enable non-restrained settlement of the upper part of the box during specimen contraction. 相似文献
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通过对国内外学者在岩石锚杆设计上存在的差异的探讨,认为检测手段的差异是产生认识差异的主要原因.国内锚杆检测将原始地面作为反力装置进行锚杆抗拔试验,千斤顶的反力无形中是对地层施加荷载,使得对锚杆的变形破坏的考虑限制在(1)钢筋或其他材料本身(2)锚固段的砂浆对于钢拉杆的握固力和(3)锚固段地层对于砂浆的摩擦力是否承受极限拉力这3个方面进行考虑,而未能考虑锚固的土体在最不利的条件下需能保持整体稳定性. 相似文献
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土工格栅加筋技术对膨胀土地质灾害的防治具有特殊效果,但目前对土工格栅与膨胀土界面特性的研究不足。采用南水北调中线工程新乡段的膨胀性泥灰岩风化土作填料,塑料单向拉伸土工格栅作为加筋体,在叠环式剪切试验机上通过施加不同的竖向荷载对其界面特性进行了拉拔试验研究。研究结果表明,土工格栅在膨胀土中的拔出过程主要经过3个阶段,分别是界面静摩擦力阶段、渐进剪切阶段和整体运动阶段,各阶段受力特性有明显差异;随着法向应力的增大,静摩擦力在界面抗剪强度比值呈对数级增大,从50 kPa时0.20增大至400 kPa时0.57,极限值可达到0.75;对挡土墙、高边坡等加筋设计中应考虑最大静摩擦力所占比重,在格栅的不同竖向高度处所受垂直应力不同,分段设计更加合理。 相似文献
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Engineering classifications which are useful for “temperate” zone soils usually fail to predict the field performance of lateritic soils, because the index tests upon which the classifications are based are not always reproducible for lateritic soils. Undisturbed and disturbed samples of twelve lateritic soils from Hawaii and Puerto Rico, all derived from basalt but representing various stages of weathering were subjected to engineering and mineralogic tests. The specific gravity of the solids increases as the degree of weathering increases; and both strength and void ratio exhibit systematic trends with increased weathering. These results suggest a classification based upon specific gravity and void ratio. Soils with specific gravities less than 3.05 and void ratios greater than 1.25 have low cohesion (less than 20 psi) and low internal friction angles (less than 35°); whereas soils with void ratios between 1.25 and 0.9 have higher cohesions. Still greater values for cohesion and friction angles are noted in soils with void ratios lower than 0.9. Soils with specific gravities greater than 3.05 and void ratios greater than 1.25 have low cohesion but high friction angles. Thus by measuring the void ratio and specific gravity of these soils one can estimate their strength. 相似文献
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吸力内摩擦角在非饱和土抗剪强度理论中是一个关键参数,因受设备、测试技术以及试验方法等的限制,对于其值的确定难度较大。详细地分析了土的基本物理力学性质、测试方法对吸力内摩擦角数值的影响,并通过定性分析和定量计算结合,认为干密度、含水率、内摩擦角、黏聚力与吸力内摩擦角之间存在着一定的非线性关系,因而借用人工智能--BP神经网络的方法构建了4:9:1的网络结构模型,实现了对吸力内摩擦角 的预测和计算。通过预测结果的分析可知,该模型模拟和预测的精度均较高,因此,该种方法可以应用到非饱和土吸力内摩擦角值的预测之中去。 相似文献
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B.P. Wen A. Aydin N.S. Duzgoren-Aydin Y.R. Li H.Y. Chen S.D. Xiao 《Engineering Geology》2007,93(3-4):82-98
Slip zones of the large landslides in the Three Gorges area are commonly composed of fine-grained soils with substantial amount of coarse-grained particles, particularly gravel-sized particles. In this study, residual strength of the soils from slip zones of these landslides were examined in relation to their index properties based on a survey of 170 landslides. It was found that laboratory-determined residual friction angle using gravel-free fraction of the disturbed soils from the slip zones was closely related to clay content, liquid limit and plasticity index. On the other hand, in-situ residual friction angle of these soils (i.e. including gravel fraction) showed very weak correlations with clay content and Atterberg limits, but was largely dependent on gravel and fines (clays + silts) contents, increasing with gravels and decreasing with fines, and displayed strong linear correlation with the ratio of gravel to fines contents. These observations indicate that among the index properties, clay content and Atterberg limits can be used to estimate residual strength of the soils finer than 2 mm, but they are not appropriate evaluate the residual strength of the soils containing considerable amount of gravel-sized particles. For the latter, particle size distribution (particularly the ratio of gravel to fines contents) appears to be a useful index. Additionally, it was found that there was no identifiable correlation between relative abundance of individual major clay minerals and residual friction angles of both gravel-free fraction of disturbed and in-situ soils, suggesting that influence of clay minerals on residual strength of these soils can not be simply evaluated based on their abundance. 相似文献