Prediction of ground surface displacement caused by grouting

Ground surface displacement caused by grouting was calculated with stochastic medium theory. Ground surface displacement was assumed to be caused by the cavity expansion of grouting, slurry seepage, and slurry contraction. A prediction method of ground surface displacement was developed. The reliability of the presented method was validated through a comparison between theoretical results and results from engineering practice. Results show that the present method is effective. The effect of parameters on uplift displacement was illustrated under different grouting conditions. Through analysis, it can be known that the ground surface uplift is mainly caused by osmosis of slurry and the primary influence angle of stratum β determines the influence range of surface uplift. Besides, the results show that ground surface uplift displacement decreases notably with increasing depth of the grouting cavity but it increases with increasing diffusion radius of grout and increasing grouting pressure.

A new analytical solution for calculation the displacement and shear stress of fully grouted rock bolts and numerical verifications

In presence of difficult conditions in coal mining roadways, an adequate stabilization of the excavation boundary is required to ensure a safe progress of the construction. The stabilization of the roadways can be improved by fully grouted rock bolt, offering properties optimal to the purpose and versatility in use. Investigations of load transfer between the bolt and grout indicate that the bolt profile shape and spacing play an important role in improving the shear strength between the bolt and the surrounding strata. This study proposes a new analytical solution for calculation displacement and shear stress in a fully encapsulated rock bolt in jointed rocks. The main characteristics of the analytical solution consider the bolt profile and jump plane under pull test conditions. The performance of the proposed analytical solution, for three types of different bolt profile configurations, is validated by ANSYS software. The results show there is a good agreement between analytical and numerical methods. Studies indicate that the rate of displacement and shear stress from the bolt to the rock exponentially decayed. This exponential reduction in displacement and shear stress are dependent on the bolt characteristics such as: rib height, rib spacing, rib width and grout thickness, material and joint properties.

Experimental Study on Mechanical Characteristics of Cracked Rock Mass Reinforced by Bolting and Grouting

The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealedby means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting andgrouting. And the load-bearing mechanism of the reinforced rock mass was perfectly reflected by the experiment. Theresults can offer some useful advice for support design and stability analysis of deep drifts in unstable strata.

运营期纵连板式无砟轨道端刺结构位移特征

研究目的:Π型端刺锚固体系是纵连板式无砟轨道路桥过渡段限制轨道结构位移的关键部位。本文考虑轨道结构与桥梁及摩擦板、端刺与土体的非线性相互作用关系,建立轨道-桥梁-路基-端刺结构一体化计算模型,研究锚固结构服役状态下的位移特征,分析端刺与路基不同脱空位置对结构位移的影响,提出注浆填补层间脱空的增强方案,并对其可行性进行论证。研究结论:(1)端刺与路基完全脱空后,纵向位移相比脱空前大幅增加且超过了3 mm位移限值,脱空引起的路基对端刺结构摩阻力、锚固力下降会导致端刺产生超量位移;(2)摩擦板区域的脱空对端刺位移影响很小,主端刺区域脱空和完全脱空引起的端刺纵向位移只相差0.11 mm,所以主端刺区域路基脱空是引发结构超量位移的主因;(3)采用注浆方式对脱空区域路基进行加固整治后端刺的纵向位移降低了3.5 mm左右,端刺结构位移恢复到了与正常服役状况相近的程度;(4)本研究成果可为现场Π型端刺结构超量位移整治提供一定的理论依据。

运营盾构隧道洞内注浆修复试验研究

[目的]盾构隧道结构发生横截面大变形后,若采用内张钢圈等方法进行加固,会花费大量材料和人工成本。通过二次注浆改善盾构隧道结构受力条件、主动回调变形是更加经济的手段。因此有必要对注浆修复盾构隧道结构横截面变形的有效性、注浆过程中及注浆后的结构响应进行深入研究。[方法]依托武汉地铁盾构隧道进行现场洞内注浆试验,测量、比较了注浆前后隧道的周边地层缺陷、结构裂缝及收敛变形。详细分析了洞内侧向注浆后隧道结构收敛变形、水平平移的时变规律。[结果及结论]试验结果证明了洞内侧向注浆对修复地层缺陷、治理隧道结构裂缝和横截面大变形的有效性;揭示了注浆荷载影响下衬砌环的收敛变形、水平平移的分布规律和时变发展过程。在注浆过程中,注浆点位所在的衬砌环呈现“竖鸭蛋”收敛变形趋势;注浆后2.5 h,受浆液收缩影响,衬砌结构“竖鸭蛋”收敛变形有所回弹,“横鸭蛋”收敛变形趋势进一步发展;注浆后20.0 h左右,隧道结构收敛变形基本稳定。

静钻根植桩施工环境效应现场试验研究

静钻根植桩采用先钻孔注浆后植桩的施工技术,可以解决传统预制桩施工过程引起的挤土效应问题。然而,静钻根植桩施工过程中钻孔和注浆过程会对周围土体产生一定扰动,目前没有相关研究。文章通过一组现场试验对静钻根植桩施工过程中的钻孔、注浆搅拌和植桩阶段对周围土体的扰动规律进行研究。静钻根植桩施工前在钻孔周围土体中埋设土压力传感器,孔隙水压力传感器和测斜管,分别测试静钻根植桩施工过程中周围土体中水平土压力,超静孔隙水压力和深层土体水平位移的变化规律。研究结果表明:静钻根植桩施工过程会对周围土体造成一定扰动,而施工完成后周围土体中的水平土压力、超静孔隙水压力和深层土体水平位移迅速恢复;当水平距离达到4D(D为钻孔直径)时,静钻根植桩施工过程基本不会对土体产生影响;试验结果可以为静钻根植桩在地铁周围等施工位移控制敏感区域的应用提供理论依据。

嵌岩低桩承台锁口钢管桩围堰设计与施工技术

昌九高铁扬子洲赣江公铁大桥西支主桥为(48+144+320+144+48)m无砟轨道钢箱桁组合梁斜拉桥。桥塔墩位于通航河道内,桥位处河床覆盖层浅,基岩强度高,基础由大直径钻孔桩和矩形嵌岩低桩承台组成,承台采用锁口钢管桩围堰施工方案。G33号主墩围堰平面设计尺寸54.56 m×28.52 m,锁口钢管桩采用Q345B材质∅1020 mm螺旋钢管,长28 m,钢管桩之间采用C-T形锁扣连接;围堰设置4层内支撑,单层内支撑设3道对撑,内支撑四角设型钢斜撑;基底设置混凝土垫层参与围堰结构受力。围堰采用XR360旋挖钻机在岩层中引孔,孔内换填细砂后插打钢管桩,钢管桩壁内、外两侧换填砂采用高压旋喷注浆加固。围堰设置智能化监测系统,对围堰受力、变形等进行实时动态监控。实践证明,该桥围堰结构安全可靠、止水效果良好、施工快捷高效。

工业灰渣-棉秆纤维灌孔砌块砌体的抗剪性能研究

为研究工业灰渣-棉秆纤维灌孔砌块砌体的抗剪性能,对48个工业灰渣-棉秆纤维灌孔砌块砌体和6个未灌孔工业灰渣-棉秆纤维空心砌体进行了抗剪试验,探究了砌筑砂浆抗压强度、芯柱抗压强度和预压力对灌孔砌块砌体破坏特征、峰值位移和抗剪强度的影响,分析了灌孔砌块砌体的剪切变形性能。结果表明:提高砂浆抗压强度、芯柱抗压强度和预压力均能不同程度地提升灌孔砌块砌体的抗剪强度和峰值位移,其中芯柱抗压强度和预压力对砌体抗剪强度和峰值位移影响较大;与砂浆部分相比,随着芯柱抗压强度的提升,芯柱部分对砌体抗剪强度的贡献越来越大。基于梁式抗剪模型,提出了适用于无预压状态下工业灰渣-棉秆纤维灌孔砌块砌体的抗剪强度计算公式;根据试验结果拟合了预压状态下砌体的抗剪强度计算公式。

运营高铁高压喷射注浆桩桥墩纠偏技术

以广珠城际铁路沙朗特大桥为研究对象,基于弹性地基梁原理,利用高压喷射注浆桩的喷射压力进行桥墩及桥台的纠偏,建立高压喷射注浆桩的桥墩纠偏联动装置模型,提出纠偏技术并得到成功应用。实施结果表明:通过高压喷射注浆桩纠偏后桥梁及轨道结构状态稳定,为恢复桥梁正常使用功能,对偏移量大于5 mm地段桥墩原则上应进行纠偏处理,对偏移量小于5 mm地段桥墩结合前后墩台偏移值进行判定。

高压旋喷桩单桩施工挤土效应数值模拟分析

为研究高压旋喷桩加固区域近接既有高速铁路时,高压旋喷桩施工造成周围土体变形的规律,依托杭甬高速铁路198号桥墩所在断面,结合现场试验,采用有限差分软件FLAC3D模拟高压旋喷桩施工,探究高压旋喷桩单桩注浆压力、桩长和土体模量变化对挤土效应范围的影响。结果表明:(1)现场试验中单桩挤土效应影响距离约16.5 m,占桩长的82.5%;(2)高压旋喷桩单桩施工挤土效应影响距离与注浆压力、桩长呈正相关;(3)单桩注浆压力增大,桩长增长,挤土效应影响距离增大;(4)桩周土体模量增大,高压旋喷桩的挤土效应影响距离减小;(5)高压旋喷桩近接既有高速铁路施工时,需确定正确施工参数并进行变形监测,必要时采取变形控制措施。

MJS高压旋喷桩在基坑支护工程中的应用研究

以南京市中山北路202号地下车库项目基坑支护工程为例,研究不同支护方案下秦淮河漫滩区深基坑开挖过程中支护结构的支护效果。采用ABAQUS有限元分析软件研究MJS高压旋喷桩单排悬臂桩支护、内支撑排桩支护这两种支护方案在施工过程中桩身水平位移、桩后地表沉降、桩身弯矩的变化。结果表明:内支撑排桩支护效果较单排悬壁桩更佳,基坑开挖过程中施加内支撑可以调整桩身受力,有效控制基坑变形;单排悬壁桩支护结构受土体的开挖深度影响较大,一般适用于地质条件较好深度较浅的基坑中。

Complete load transfer behavior of base-grouted bored piles

A field study on the behavior of three destructive piles in soft soils subjected to axial load was presented.All the three piles with different diameters were base-grouted and installed with strain gauges along the piles.The complete load transfer behavior of the base-grouted pile was analyzed using measured results.Moreover,the thresholds of the relative pile-soil displacement for fully mobilizing skin frictions in different soils were investigated,and pile tip displacements needed to fully mobilize tip resistances were analyzed.The results of the full-scale loading tests show that the skin frictions are close to the ultimate values when the pile-soil relative displacements are 1%-3% of pile diameter,and the pile tip displacements needed to fully mobilize the tip resistances are about 1.3%-2.0% of pile diameter.The load transmission curve of the soils around the pile tip corresponds to a softening model when the pile is loaded to failure.

Similarity Solution for the Synchronous Grouting of Shield Tunnel Under the Vertical Non-Axisymmetric Displacement Boundary Condition

Abstract.Similarity solution is investigated for the synchronous grouting of shield tunnel under the vertical non-axisymmetric displacement boundary condition in the paper.The synchronous grouting process of shield tunnel was simplified as the cylindrical expansion problem,which was based on the mechanism between the slurry and stratum of the synchronous grouting.The stress harmonic function on the horizontal and vertical ground surfaces is improved.Based on the virtual image technique,stress function solutions and Boussinesq’s solution,elastic solution under the vertical non-axisymmetric displacement boundary condition on the vertical surface was proposed for synchronous grouting problems of shield tunnel.In addition,the maximum grouting pressure was also obtained to control the vertical displacement of horizontal ground surface.The validity of the proposed approach was proved by the numerical method.It can be known fromthe parameter analysis that larger vertical displacement of the horizontal ground surface was induced by smaller tunnel depth,smaller tunnel excavation radius,shorter limb distance,larger expansion pressure and smaller elastic modulus of soils.

定向区域注浆三维模拟试验系统研制及应用

定向区域注浆改造含水层是矿井水害防治的有效途径之一。为研究定向区域注浆浆液扩散规律,自主研制了定向区域注浆三维模拟试验系统。该系统主要由试验台、注浆系统、注水系统及数据监测等子系统组成,可实现定向钻孔注浆模拟、浆液三维扩散模拟、高承压水模拟和区域化注浆模拟等功能。系统可独立控制注浆孔单元,实现多孔、多序次注浆,借助6个注浆孔模拟不同注浆压力、浆液黏度、注浆速率、水灰比等多种参数影响下的浆液流动过程,并可实现动/静(高)水压环境下浆液扩散过程的实时监测。以200、250、300 mm模拟裸孔长度为研究对象,初步探究了定向注浆作用下裸孔注浆浆液扩散的特征及其效果。研究发现:在仅有裸孔长度为变量的情况下,浆液扩散范围不会随裸孔长度的线性增加而同步线性增加;短裸孔的浆液结石体呈现以钻探裸孔为轴心的圆柱状,长裸孔的浆液结石体呈现以钻探裸孔为轴心的圆台状;裸孔增加相同的长度,裸孔越长,浆液在裸孔两端的扩散范围差值越大,同时压力损失越多,浆液扩散的距离越小。将试验所得浆液扩散半径与Maag公式计算所得浆液扩散半径进行对比,发现注浆裸孔长度为200 mm时,两数值仅相差2.8%,试验结果符合Maag球形扩散理论规律,验证了本试验系统的科学性与合理性。

基于地表位移控制的浅埋盾构管片壁后注浆压力确定方法

采用考虑卸载模量的硬化土小应变模型,模拟分析了不同埋深盾构隧道施工时地表竖向位移随管片壁后注浆压力的变化规律,并从盾构施工微扰动控制角度探讨了壁后注浆压力的确定方法。结果表明:随壁后注浆压力增大,不同埋深下地表竖向位移均可分为沉降敏感阶段、稳定阶段和隆起敏感阶段;壁后注浆压力应在隧道顶部上覆土自重应力的基础上进一步增大,以顶起上覆土,弥补超挖引起的地表沉降;当地层损失补偿率与地层损失率接近时,可达到盾构施工微扰动控制要求,据此提出一种综合考虑地表竖向位移、地层损失率、地层损失补偿率的壁后注浆压力范围确定方法。

高压气囊桩对既有地铁隧道的安全保护试验研究

近接基坑施工可使既有地铁隧道出现较大的应力和发生变形。为此,本文对高压气囊桩地铁保护技术进行优化,并在宁波轨道交通5号线前殷停车场入场线开展高压气囊桩对既有地铁隧道的安全保护现场试验。通过测定隧道的水平位移、沉降和收敛以及高压气囊桩周边的孔隙水压力、深层水平位移、分层沉降,评估了高压气囊桩对隧道的安全保护作用效果。结果表明:布设在隧道近侧的高压气囊桩充气加压和压力注浆使得隧道产生背离桩体的最大水平位移为1.65mm和最大沉降为1.01mm,可以对既有地铁隧道水平位移起到较好的保护作用。

邻近高速铁路单根高压旋喷桩施工对周围土体的变形影响

为研究邻近既有高速铁路高压旋喷桩施工引起的周围土体变形规律,本文以实际地基加固工程为背景,采用现场试验与有限元模拟相结合的方法,明确了单根高压旋喷桩的施工影响距离,分析了高压旋喷桩的施工参数对周围土体变形的影响,提出了邻近高速铁路的高压旋喷桩施工注意事项。研究结果表明:现场试验的单根桩施工影响距离约占桩长的80%,有限元模拟的影响距离占桩长的78.9%,旋喷桩周围土体的最大水平位移及单根桩的影响距离将随着钻杆提升速度减小及注浆压力增大而增大,当邻近高速铁路进行高压旋喷桩施工时,应确定适宜的施工参数,加强对既有高速铁路的变形监测,必要时在施工前采取一定的变形控制措施。

黄土地区高压旋喷桩施工挤土效应预测方法研究

高压旋喷桩作为一种方便高效的复合地基加固措施,适用于湿软黄土地区路基帮宽段地基加固。高压旋喷桩施工注浆期间中会挤压周边土体产生变形,从而影响线路的安全运营。以某高速铁路引入既有城际铁路路基帮宽段工程为背景,通过对高压旋喷桩单桩施工挤土过程的简化分析,将施工注浆过程简化为半无限土体中一系列球形空腔膨胀的过程,提出了考虑施工参数与土体参数的单根高压旋喷桩施工引起土体位移的计算方法;给出了施工结束时土体侧向位移及垂向位移计算公式;根据量纲分析提出了球形空腔半径的计算公式,并将理论预测结果与现场试验结果进行对比,证明了该方法的可靠性。通过该方法进行参数化分析,结果表明:随着土层深度的递增,土体垂向位移不断减小,侧向位移先增大后减小;黄土地区单桩施工影响范围约为10倍成桩半径。

含断层采场顶板膨胀型浆体注浆加固效果研究

为研究某矿含断层采场顶板处采用膨胀型浆体注浆加固效果,开展了由膨胀型浆体和普通型浆体注浆加固相似模拟试验,对比分析了不同浆体注浆加固后含断层采场顶板沉降和围岩应力变化情况。研究结果表明:相较于普通型浆体,膨胀型浆体注浆加固含断层采场顶板能够进一步减小顶板沉降及其上下盘围岩应力增量,使加固后的含断层采场顶板稳定性更高;膨胀型浆体通过先挤后黏增加了浆—岩接触面的粘结强度和摩擦强度,提升了复合顶板整体力学强度和承载力,减小了上覆岩层自重应力向矿柱围岩中底部转移;膨胀型浆体产生的膨胀应力分别向上支撑和向下挤压断层两侧岩体,缓解了上覆岩层对上盘岩体矿柱围岩的挤压,略微增大了下盘矿柱的围岩应力。

高性能灌浆料置换RC框架边节点高温后抗震性能

对C30混凝土整浇梁柱边节点和UGM高性能灌浆料置换加固梁柱边节点进行了高温试验和低周往复加载试验,对比了节点的破坏形态,分析了节点的滞回特性、承载性能、耗能能力和延性,研究了高温对两种节点抗震性能的影响规律。结果表明:在500℃范围内,随着温度的升高,C30节点和灌浆料加固节点的变形能力不断提升,承载力、耗能能力基本上呈现不断降低的趋势,延性则先提高而后降低,但仍大于常温状态下的延性系数,同时,灌浆料加固节点的抗震性能总体上优于C30节点。