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建立了基于弹性理论法的抗拔单桩解析计算模型,以及考虑试桩与锚桩相互作用的群桩计算模型,利用该计算模型讨论不同地层中抗拔桩桩身变形和内力分布规律,进而分析锚桩法静载试验中地层条件、桩间距等因素对试桩竖向抗压刚度和变形的影响。计算结果表明,桩土刚度比越大,桩-土界面摩阻力和桩身轴力曲线沿深度变化越小,相应桩身上拔位移量越大。土体模量大的地层中桩身轴力衰减最快,浅部土层性质对单桩抗拔承载力起重要作用。试桩、锚桩与地基相互作用可导致锚桩法静载试验中试验桩抗压刚度比真实情况偏大,对静载试验结果修正后能得到与实际情况更为接近的试桩曲线。 相似文献
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基于气压沉箱中同时具有防突沉支承力与助沉拉反力的锚桩设计与施工研究,发现锚桩经工况分析以抗拔承载力为主控,并可根据所处边界条件与常规应用的不同,对规范中确定设计桩长和桩径的公式进行合理调整,同时考虑节省投资,引入桩底后注浆与桩侧后注浆技术。在施工过程中通过自主开发的自动控制装置控制沉箱,使锚桩承压与抗拔承载作用于一体,很好做到了防突沉与助沉控制一体化,可供相关借鉴参考。 相似文献
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基于Abaqus软件,建立桩土有限元模型研究了扩底桩在上拔荷载作用下的承载性状。结果表明:扩底桩达到抗拔极限承载力时,桩底与土体产生了分离,扩底桩抗拔承载时的桩身轴力在扩大头的上下出现突变,扩大头承受了桩的大部分荷载,塑性应变主要发生在扩大头附近的土体中。 相似文献
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应用基于 Mindlin 位移解的弹性理论法建立了堆载法和锚桩法单桩静载测试过程的理论模拟方法,对两种测试方法进行了对比分析。重点研究了基准桩布置对两种测试方法结果的影响,结果表明:堆载法和锚桩法测试均夸大了单桩刚度,且锚桩法比堆载法更明显;另外,按照现有桩基检测规范进行的桩基测试在一定的条件下对单桩刚度的影响较大。要充分利用压重平台卸荷或锚桩上拔引起基准桩的上抬和测试桩桩身应力引起基准桩的下沉叠加来降低对测试结果的影响。 相似文献
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Influence of installation method on performance of screwed pile and evaluation of pulling resistance
In the present study, we performed installation and pull-out loading tests on screwed piles in sand deposits using a calibration chamber. These tests focused on how the installation method influenced the performance of the piles. The results revealed that the load-displacement relationship strongly depended on the installation method, but that the second-limit uplift resistance was almost unaffected. Next, we observed the movement of the soil near the pile after both the installation and pull-out loading tests. Shear failure of the soil, which occurs in a cylindrical region in the periphery through which the wing plate of the pile passes, regardless of how the screwed pile is installed, was found to be one of the determinants of the pulling resistance. Finally, we evaluated the pulling resistance of the screwed pile based on these soil observations and an analysis of the loading test results. We found that the pulling resistance of the wing plate could be determined based on the change in earth pressure near the pile due to installation and pull-out loading of the pile. 相似文献
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延安市体育场采用人工挖孔大直径嵌岩灌注桩,从桩基受力机理方面分析了采用嵌岩桩的优越性。与扩底灌注桩相比,嵌岩桩充分发挥了嵌岩段的侧壁摩阻力和桩端阻力,节省了桩端扩底需开凿粗砂岩的工作量,避免了因扩底而丧失斜面高度范围内的侧阻力。嵌岩桩能大幅提高单桩竖向承载力,减少柱下布桩的数量和承台尺寸。单桩竖向抗压静载荷试验检验了设计方法的正确性。介绍了该桩的设计参数及静载荷试验结果,可供同类工程设计时参考。 相似文献
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在钻孔灌注桩桩基工程中,为确保整个工程的安全性,需要进行桩基静载试验。传统的方法有锚桩法和自平衡法,本文以顾乡堤大桥为依托背景,对现场同一地区的两根工程桩分别采用锚桩法与自平衡法分别进行试验,对桩侧摩阻力,桩的承载力性能以及桩端阻力进行对比分析,探讨了两种方法的一些差异。 相似文献
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通过3桩等边三角形承台原型群桩基础的4次斜向抗拔、2次垂直抗拔和5次单桩垂直抗拔试验,绘制了相应的荷载位移关系曲线。依据地基变形特点和曲线变化特征,建议采用具有明确物理特征的H-(△x/△H)曲线判定螺旋群桩基础水平方向极限荷载,垂直方向抗拔极限荷载依据单位荷载的桩顶位移变化率、桩顶位移增量以及地基变形特征判定,并讨论了群桩基础在斜向荷载和垂直荷载上拔过程中的群桩效率。试验表明:抗拔群桩基础的群桩效率与外荷载的作用角度有关,斜向抗拔螺旋群桩基础的群桩效率小于垂直抗拔群桩基础的群桩效率,荷载水平分量加快了该种群桩基础的上拔破坏,斜向抗拔群桩的极限破坏荷载和极限位移要小于垂直抗拔螺旋群桩基础。 相似文献
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在乌江构皮滩水电站水垫塘及边坡存在页岩、黏土岩、粉砂质黏土岩,且夹薄层泥灰岩和少量中细粒钙质砂岩,为典型的不均质软岩,为了克服运行期间的浮托力,设计采用1 200多根锚桩对该层软岩进行锚固,则锚桩的极限承载力、群桩的间距和锚固深度等3个主要指标需要通过原位试验确定。将地表变形测量和深部应力测量的一般方法应用于锚桩的径向变形和轴向应力影响范围测量,进行了5根锚桩抗拔试验,并设计了一套试验方法。通过研究不同边界条件下锚桩的破坏形式,确定了锚桩的极限承载力标准值。通过测试锚桩周围岩体铅直方向上抬变形沿径向的分布规律研究了锚桩对软岩的影响范围,确定群桩间距为12D(D为桩径),通过预埋钢筋计测试不同深度的应力大小,研究了锚桩深部应力的分布规律并确定了锚桩的锚固深度为42D。 相似文献
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《Soils and Foundations》2014,54(2):168-175
The jet mixing anchor pile is a new kind of supporting technology for foundation pit engineering in soft clay. The engineering features of jet mixing anchor pile as well as the difference between it and normal anchor bolt are introduced. The uplift tests of 4 jet mixing anchor piles are presented in detail to obtain the ultimate bearing capacity and load–deformation relationship of the piles. Load-transfer analysis, which is rarely applied in the analysis of uplift piles, is carried out on the piles with a hyperbolic calculation model. The load transfer method focuses on the interface between pile and soil, with which the non-linear behavior, the bearing capacity and the engineering features of the anchor piles can be fully studied. The calculated load–displacement curves of the piles have close agreement with that of the pullout tests, indicating that the proposed analytical solution is reasonable and feasible in predicting the bearing capacity of the piles. Thus, with this study, the supporting stiffness of the anchor pile can be predicted in the design stage of the foundation pit engineering, which is very important and meaningful in practical engineering. The decay curve of shear stress of soil surrounding the pile is derived with the load-transfer method, through which the minimum transverse space of each two piles can be decided against the pile group effect. Engineers can optimize the length and spacing of group piles through this. 相似文献
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针对某体育馆工程桩基不能满足抗拔设计要求的实际情况,通过对钻孔灌注抗拔桩受力进行分析,综合考虑桩基技术要求、应用效果与经济效益,确定出在灌注桩上钻孔,穿入抗拔锚杆并锚入基底岩石,来达到增加抗拔能力的处理方法。 相似文献
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对位于上海软土地区某6层砖混住宅采用压桩掏土法纠偏。常规压桩纠偏,先在建筑物较大一侧压桩、封桩;再在建筑物沉降较小一侧掏土纠偏,并在掏土一侧设置少量保护桩,提高建筑物回倾后的稳定性。在该工程的施工过程中,将沉降较大一侧的压桩和沉降较小一侧的掏土纠偏同时进行,并推迟沉降较大一侧的封桩,既缩短了工期,又减小了桩顶的附加应力,同时房屋的附加沉降也控制在允许范围内,取得了较好的纠偏效果。 相似文献