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1.
高浓度浆液注入到采空区后形成充填墩台,墩台搭接尺寸将影响其上覆承载力。为掌握搭接尺寸对上覆承载力影响规律,选取水泥为胶结材料,标准砂为骨料,配制高浓度浆液,并利用3D打印技术制模制作墩台试样,进行单轴抗压试验。结果表明,单个墩台在顶面面积和高度一定时堆积角度越小极限承载力越大;堆积角30°和45°的搭接墩台试样的极限承载能力均在对应的单个墩台的2.0~3.5倍范围,试样硬化后,搭接墩台试样的极限承载力随着搭接尺寸的增加呈先增大后减小的趋势;采用墩台充填的方式进行采空区治理时,合理设置注浆孔间距,使所注浆液在采空区内部形成搭接墩台群,其承载效果优于均匀分布的单个墩台;堆积角30°搭接墩台的场地承载力整体优于堆积角45°的搭接墩台;采空区内取充填堆积角30°搭接墩台,且注浆孔间距为极限搭接尺寸的38.5%时,治理场地内整体承载力最大。研究成果将为高浓度浆液部分充填治理采空区的工程实施提供依据。 相似文献
2.
通过颗粒流数值模拟,从桩端阻力随上拔位移的发展与桩端周围土体颗粒位移表现等角度,研究了扩底抗拔桩端阻力的群桩效应问题。研究比较了单桩（墩）与群桩（墩）的抗拔性状以及不同墩距下中心墩与边墩阻力随上拔位移发展的情况。研究表明,在归一化上拔量 0.1时,单桩（墩）与群桩（墩）的上拔特性无明显差别;此后,随着上拔位移的发展,单桩（墩）的上拔端阻力要大于群桩中的桩（墩）的端阻力,桩（墩）周围土体颗粒的相互影响开始显现。在归一化上拔量 0.5的情况下,群桩（墩）中中心桩（墩）的端阻力要略大于边桩（墩）。在归一化上拔量 0.5的情况下,群桩中边桩的桩端阻力较中心桩的要大,而群墩中边墩的墩端阻力较中心墩要小,体现了桩身侧限对抗拔桩群中端阻力发挥的影响。随着墩距的增大,在较大的位移量以后群墩才与单墩的受力有显著差别。 相似文献
3.
尖山营特大桥桥墩每年均出现雨季抬升,旱季沉降的异常现象。本文针对桥墩异常升降问题,采用野外地质调绘、现场监测、钻探、物探以及室内试验等方法相结合,分析造成尖山营特大桥墩体异常升降的主要原因。通过现场地质调绘和钻孔岩芯发育情况获取研究区地质构造分布,分析构造作用对异常升降的影响;基于天然音频大地电法勘探与对研究区地表水出露情况的勘察,研究承压水的赋存情况;将钻孔岩芯进行室内膨胀特性试验,研究了桥址区地基岩土体的吸水膨胀特性对桥墩升降的潜在作用。结果表明:排除地质构造和承压水原因,引起桥墩异常升降的主要原因是膨胀岩土体与地下水物理化学反应带动上部结构抬升及沉降引起的。桥址区二叠系吴家坪组（P2w）地层岩土体的膨胀力试验预估值在3～59 MPa之间,上部总荷载1.38～13.5 MPa,膨胀力大于上部结构重力载荷;原状膨胀岩试样在1.05 MPa的轴压作用下吸水,存在0.35%的膨胀应变,结合已有研究可确定130 m厚的膨胀性地层可造成上部结构抬升45.5 mm。二叠系吴家坪组（P2w）地层的吸水膨胀、失水收缩性能,与地下水的补给与排泄相结合,是引发桥墩异常升降的主要原因。 相似文献
4.
砂卵石层上大直径扩底短墩竖向承载性状 总被引：12，自引：2，他引：10
根据同一场地砂卵石层中一组土的深层静载荷试验、一组纯摩擦桩和两组原型扩底墩的竖向承载力静载试验,分析了埋深在6.20～6.75 m处的扩底短墩的荷载传递性状。结果表明,可用直接试验法和间接试验法确定扩底墩的竖向承载力。以卵石层为持力层的S3试验墩的极限承载力为7 250 kN,其中端阻力达6 890 kN,占95 %;以砂层为持力层的S2墩的极限承载力为2 330 kN,端阻力占85 %。当墩顶仅沉降1.46 mm左右时,S3、S2墩侧摩阻力已充分发挥;在端阻力充分发挥时,S3、S2墩顶沉降则分别达92.64 mm和21.07 mm。直径相同时,扩底桩的竖向承载力远大于纯摩擦桩和直身墩。 相似文献
5.
ABSTRACT Granular pile-anchor (GPA) technique is an innovative tension-resistant foundation technique which can effectively ward off the dual swell–shrink problem posed by expansive clays. The other tension-resistant foundation techniques are drilled piers, belled piers and under-reamed piles. Laboratory scale model studies and field scale experiments on GPAs revealed that swelling of expansive clay beds could be effectively controlled by GPA technique. This paper presents results obtained from laboratory scale model studies on GPA-reinforced expansive clay beds subjected to alternate cycles of wetting and drying. Swelling and shrinkage of the clay beds were monitored for three wetting–drying cycles (N) spanning a time period of 300 days. The clay beds were reinforced with varying number of GPAs (n = 0, 1, 2 and 3). Swelling (mm) and shrinkage (mm) of the clay beds in a given wetting–drying cycle decreased with increasing number of GPAs. Further, swelling (mm) and shrinkage (mm) significantly decreased with increasing number of wetting–drying cycles (N) also. For a given number of GPAs (n), swelling and shrinkage decreased with increase in depth from the top of the clay bed too. 相似文献
6.
A bridge pier supported on two drilled shafts collapsed due to the impact by a 130-ton rock in a landslide event. A series
of static and dynamic numerical simulations is conducted using a nonlinear finite element analysis program to investigate
the bearing behavior and responses of the bridge foundation under rock impact. The rock impact load is evaluated according
to the site conditions. The deflection histories at the striking point and the internal forces in the drilled shafts during
rock impacts in different directions are analyzed. The bridge pier exhibits significant system effects: the failure of the
bridge pier is initiated by the failure of one pier column or one drilled shaft first, followed by the failure of the entire
pier. The effects of impact loading direction, striking location, and characteristics of impact load on the behavior of the
bridge pier are examined through a parametric study. The capacities of the pier along different loading directions are different
due to differences in the group effects of the drilled shafts. The bridge pier is strongest when the impact load is along
the 45° direction with respect to the shaft row, and weakest when the impact load is perpendicular to the shaft row. 相似文献
7.
Jian-Feng Chen Jie Han Sadik Oztoprak Xiao-Ming Yang 《Computers and Geotechnics》2009,36(7):1191-1199
A three-dimensional numerical method was used to simulate cavity expansion during installation and an in situ load test conducted on a single rammed aggregate pier (RAP). Verification of the numerical model was carried out by comparing the computed settlements at top and tip of the pier with the measured values. An un-rammed aggregate pier (UAP) of the same diameter and length was also simulated using the numerical method to demonstrate the effect of installation. Interpretations of the numerical results were focused on the load–settlement behavior, the bulging of the pier, the axial load distributions along the pier, and the stress paths of the soil around the pier. A parametric study was conducted to investigate the influence of the pier length/diameter ratio and the soil properties on the behavior of rammed and un-rammed aggregate piers. 相似文献
8.
岩溶区隧道围岩--支护体系稳定性研究 总被引：4，自引：0，他引：4
岩溶是地下水地质作用的过程和结果，是隧道建设面临的不良地质现象之一。正在建设中的某高速公路隧道出口段岩溶地质作用强烈，溶隙、孔洞发育，且受构造变形及后期淋滤溶蚀作用强烈，力学强度低，岩性复杂。其角砾状粘土岩和水云母粘土岩多已泥化成粘土，遇水易膨胀。岩溶区隧道围岩——支护体系的稳定性是该隧道建设面临的主要问题。文章结合隧道施工过程中的围岩变形监控量测和三维弹塑性有限元数值仿真模拟对隧道围岩——支护体系的稳定性进行了研究。围岩水平收敛和拱顶下沉位移及速率变化特性表明，在监测时段内隧道围岩无趋于稳定的迹象。施工动态力学数值仿真模拟表明，在初期支护条件下，围岩出现了较大范围的塑性破坏区，两隧道之间(间距45．0m)围岩破坏接近度达到0．70，最大竖向位移达到3．0mm，表明隧道全断面施工时，两隧道相互作用影响程度较大。为确保隧道围岩——支护体系的稳定，选择合理的施工方法，制定切实可行的支护方案提供了信息。 相似文献
9.
Sudhakar M. Rao T. Thyagaraj P. Raghuveer Rao 《Geotechnical and Geological Engineering》2013,31(4):1399-1404
Compacted expansive clays swell due to crystalline swelling and osmotic/double layer swelling mechanisms. Crystalline swelling is driven by adsorption of water molecules at clay particle surfaces that occurs at inter-layer separations of 10–22 Å. Diffuse double layer swelling occurs at inter-layer separations >22 Å. The tendency of compacted clay to develop osmotic or double layer swelling reduces with increase in solute concentration in bulk solution. This study examines the consequence of increase in solute concentration in bulk solution on the relative magnitudes of the two swelling modes. The objective is achieved by inundating compacted expansive clay specimens with distilled water and sodium chloride solutions in free-swell oedometer tests and comparing the experimental swell with predictions from Van’t Hoff equation. The results of the study indicate that swell potential of compacted expansive clay specimens wetted with relatively saline (0.4, 1 and 4 M sodium chloride) solutions are satisfied by crystalline swelling alone. Comparatively, compacted clay specimens inundated with less saline solutions (0.005–0.1 M sodium chloride) require both crystalline and osmotic swelling to satiate the swell potential. 相似文献
10.
针对阳城煤矿不等长工作面台阶区域发生冲击地压灾害问题,基于工作面特殊布置方式及覆岩赋存特征,采用理论分析、数值模拟和现场实测等方法,分析了台阶区域覆岩结构运动特征和围岩应力演化规律,研究了台阶区域冲击地压诱发机制。研究结果表明：1304工作面台阶区域覆岩经历了“OX-S-C”型较为复杂的结构演变,覆岩空间结构由OX向S型转换时,顶板岩层大面积破断下沉,在台阶区域形成多个悬臂梁结构,越往高位,悬臂梁长度越大;受覆岩运动和采动应力场叠加影响,煤岩体形成高应力集中区,在顶板岩层动载冲击作用下,煤岩体弹性应变能突然释放,诱发冲击地压。采用COMSOL软件对不同卸压钻孔参数下煤体应变能分布特征进行模拟研究,优化了台阶区域卸压钻孔参数。根据模拟结果,随着钻孔孔径、孔深增大及间距减小钻孔卸压效果越明显,考虑工程实际,确定孔径为150 mm、孔深为30 m、间距为1 m为合理有效的卸压钻孔参数,并应用于1302工作面台阶区域的冲击地压防治,取得了较好的防冲效果。 相似文献
11.
上海地铁12号线龙漕路车站基坑下穿运营3号线高架,施工条件受限,需要对位于基坑中间的高架桥墩进行保护以确保3号线运营安全。依托该工程,采用精细化三维数值分析、室内试验和现场实测等方法,对近距离开挖卸荷引起的高架桥墩响应进行研究。监测结果表明：软土地层高架桥墩在近距离开挖卸荷影响下均产生上抬,与数值分析结果吻合;桥墩水平位移总体上朝向卸荷一侧,但发展过程中震荡明显且位移较大,位移终值基本符合数值分析的预估值;近距离卸荷导致桥墩基础桩极限承载力有轻微的损失,但基本不会威胁高架桥的安全;长期沉降表现为半周卸荷条件下上抬可略有恢复,全周卸荷下则不会恢复。 相似文献
12.
黄河西霞院工程电站厂房地基为上第三系洛阳组黏土岩类地层。现场勘察揭示该黏土岩具有特殊的工程地质性质,在开挖或遇水时风化分解较快,由岩石的性质转变为土的性质。为了更好地了解洛阳组黏土岩的工程特性,进行了一系列室内试验和现场大型剪切试验。该黏土岩的黏土含量最高达53.7 %,黏土矿物成分以蒙脱石为主,含量在28 %～38 %,岩体的膨胀率为0.6 %～4.9 %,单轴抗压强度为0.11～1.04 MPa,凝聚力为132.2 kPa,内摩擦角为22.29°。研究表明洛阳组黏土岩具有典型的软岩硬土特征。 相似文献
13.
浅谈当宜高速公路膨胀土性质与路基稳定问题 总被引：4，自引：2，他引：2
当宜高速公路沿线存在有大量膨胀土, 为使其加固方案合理, 避免滑坡、塌方等现象的发生, 结合当宜高速公路膨胀土试验研究及稳定性分析, 对沿线膨胀土性质与路基稳定问题进行了分析探讨, 并提出了有针对性的处治方案. 相似文献
14.
A variational model for the analysis of axially loaded piers is presented. A closed-form solution technique employing an iterative procedure, is developed to obtain the displacement and forces in the pier along its axial direction. The method is suitable for similar analyses of pile foundations. It is shown that displacements and the load distribution along the axis of the pier compare well with a more sophisticated finite element solution. Furthermore, the new model complements the well-known Reese model employing t–z curves for the analysis of settlement of axially loaded piers. This new formulation using continuum mechanics principles, distributes the work done by the applied load as compressive strain energy in the pier, and as shear strain energy in the soil, as well as, the compressive strain energy in the soil surrounding the pier and at the bottom of the pier. 相似文献
15.
高放废物地质处置黏土岩处置库围岩研究现状 总被引：2，自引：0，他引：2
世界上很多国家都对处置库的可能围岩进行了详细研究。通过对比,认为花岗岩、黏土岩、岩盐比较适合作为处置库围岩,而黏土岩由于具有自封闭性、渗透率低等其他岩石类型不可比拟的优点,因而将黏土岩作为高放废物地质处置库围岩越来越受到各国的关注。文章同时介绍了瑞士、法国、比利时等国家在黏土岩中所进行的大量研究,均认为在黏土岩中处置高放废物和乏燃料是安全的。文章还对黏土岩处置库概念设计、黏土岩处置库围岩地下实验室研究,以及我国开展黏土岩处置库研究的意义等进行了综述。 相似文献
16.
Mehrdokht Mohajerani Pierre Delage Jean Sulem Mohammad Monfared Anh Minh Tang Behrouz Gatmiri 《Rock Mechanics and Rock Engineering》2014,47(1):131-142
There are very few data on the thermoplastic behaviour of claystones, while their knowledge is necessary in understanding long-term behaviour of high-level radioactive waste confining systems. In this paper, a number of thermomechanical parameters of the Callovo–Oxfordian claystone, the possible host rock of radioactive waste in France, are presented. These parameters were obtained from experiments performed on a hollow cylinder cell. The short drainage path of this device allows a good saturation in a reasonably short time; also, the good drainage conditions and reasonable homogeneity of pore pressure during the tests in such a low-permeability material. The saturation procedure was performed under in-site stresses prior to testing to reduce the swelling effect during hydration. The thermomechanical experimental programme conducted here evidenced a plastic contraction of the claystone during drained heating under in-situ stress conditions, like in normally consolidated soils. Previous loading induced a dilating–contracting response comparable to that of overconsolidated clays. Finally, whereas the elastic response appeared to be temperature independent, the plastic compressibility investigated through a drained isothermal isotropic compression test at 80 °C increased compared to that at 25 °C. These first results should be confirmed by further thermomechanical investigation on claystones. 相似文献
17.
膨胀岩边坡工程中膨胀与流变的耦合效应 总被引：3，自引：0，他引：3
根据南昆线膨胀岩的膨胀粘滞性质，提出了将膨胀问题转化为膨胀－流变问题的力学模型，继而建立膨胀和流变的耦合模型，通过有限元计算，得到由膨胀和流变共同作用生成的附加应力及其分布规律，并对挡墙设计提出合理建议。 相似文献
18.
A mixture of the MX80 bentonite and the Callovo-Oxfordian (COx) claystone were investigated by carrying out a series of experiments including determination of the swelling pressure of compacted samples by constant-volume method, pre-swell method, zero-swell method and swell–consolidation method. Distilled water, synthetic water and humidity controlled vapour were employed for hydration. Results show that upon wetting the swelling pressure increases with decreasing suction; however, there are no obvious effects of synthetic water chemistry and hydration procedure on the swelling behaviour in both short and long terms. For the same initial dry density, the swelling pressure decreases with increasing pre-swell strain; whereas there is a well defined logarithmic relation between the swelling pressure and final dry density of the sample regardless of the initial dry densities and the experimental methods. It was also found that swelling pressure depends on the loading-wetting conditions as a consequence of the different microstructure changes occurred in different conditions. Furthermore, it was attempted to elaborate a general relationship between the swelling pressure and the final dry density for various reference bentonites. 相似文献
19.
Shales or highly compacted engineered clay layers are being used as buffers in deep surface nuclear waste repositories. Due to the complex natural structure and fabric of clay and non-clay minerals associated with high in situ stresses, high temperatures, and the practical difficulties in the replication of the field stress and temperature conditions in the lab testing facilities, swell potential from the macro and micro investigations does not provide reliable and universally applicable results. In this study, a comprehensive molecular-level simulation-based volume change constitutive model has been developed for clay minerals incorporating the effects of cation exchange capacity, density, water content, in situ stress state, temperature, exchangeable-cations type and proportion, pore fluids, and the dissolved salts. The molecular simulations were performed using molecular mechanics, molecular dynamics, and Monte Carlo simulation techniques. Comparing the model predictions with the results of the lab tests, the model has been proven to be quite precise in the prediction of the swell potential of these strata under various overburden pressures and temperatures. There is several fold increase in swelling of clay samples at 80 °C as compared to the equivalent specimen tested at 25 °C. The effect of higher temperature is lesser at lower initial water content (higher density) while at higher water content (lower density) the structure has been found to be more vulnerable at higher temperatures. About 100 times higher confining pressure results in the same swell at 80 °C as in its counterpart specimen at 25 °C, the corresponding swell increase factor in case of 50 °C specimens is about 45. A sharp increase in swelling with a drop in in situ pressure emphasizes the probability of higher swell as a result of an accidental reduction in in situ pressure such as the higher concentration of nuclear reactions. In this study, the cohesive energy density (CED) was found to be highly sensitive to various volume change variables, such as water content, density, CEC, type, and percentage of exchangeable and non-exchangeable cations. Contrary to all the previous models, CED-based model developed in this study is universal in nature and can be adopted for any case with minimal basic material input parameters. The good agreement found between the predicted and real values for the swell potential of the undisturbed samples suggests that the model presented here can effectively be used for the assessment of the swelling potential of shale/clay deposits to be used as buffers to the nuclear waste storage. 相似文献
20.
Analysis of time-varying rainfall infiltration induced landslide 总被引：5，自引：0，他引：5
Chen Chien-Yuan Chen Tien-Chien Yu Fan-Chieh Lin Sheng-Chi 《Environmental Geology》2005,48(4-5):466-479
A case study of rainstorm-induced landslide is modeled following the hourly rainfall time series from the stage of infiltration
caused by induced slope movement and soil saturated to excess pore pressures—Transient Rainfall Infiltration and Grid-based
Regional Slope-Stability Analysis (TRIGRS). The grid-based landslide stability analysis was conducted to model the increased
pore pressures and runoff in the study area under the specified rainfall conditions. The generated time variances of pore
pressures help determine landslide characteristics and mechanisms under rainfall conditions. Inputs of soil properties and
permeability parameters for landslide stability analysis in the study area were prepared by TRIGRS adopted for transient infiltration
analysis. Results of the analyses show that under heavy rainfall conditions, the infiltrated slope is unstable and the time
of debris masses movement initiated is correlated to the recorded time. In the initiated landslide, characteristics and effects
are considered and reflected in the numerical modeling under combinations of topography, land use, climatic and geological
conditions. Results reveal that there is a plane failure surface and a potential circular failure surface at the study site
besides the rock topple failures in the crest. A grid-based slope-stability analysis incorporated with the GIS spatial functions
is more advantageous than the traditional two-dimensional analysis for specified slope profiles to determine the whole behavior
of a slope. 相似文献