共查询到20条相似文献，搜索用时 15 毫秒
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Agostinho Mendonça M-Lurdes Lopes Margarida Pinho-Lopes 《Geotechnical and Geological Engineering》2003,21(2):129-147
A geogrid reinforced steep slope was built and monitored during construction and during the first ten months of service. The slope is located between Régua and Reconcos in the new Portuguese main itinerary, IP3, and is a part of reestablishment 2. The reinforced slope has an extension of about 206.2m, is in curve and the reinforced area reaches a maximum height of about 19.6m in the outside curve slope at 150.0m of extension (km 0+150). The monitored slope cross section is at km 0+150. The reinforcements are high density polyethylene geogrids;. materials with different tensile strength values were used. The reinforcement strains were measured at three reinforcement levels using linear extensometers. The soil vertical stresses were recorded using load cells. The internal horizontal displacements of the slope were recorded using two inclinometer tubes. The face displacements were recorded topographically in points spaced approximately 1.2m vertically along the face of the slope on the km 0+150 cross section. The reinforced slope behaviour was observed during a period of about 13 months, which includes three months of construction period. This way it was possible to obtain information about the slope behaviour during and after construction (the first 10 months of service). The behaviour of the observed reinforced slope is characterized by: low values of face displacements, slope internal horizontal displacements and reinforcement strains; change of the face displacements configuration at the end of construction during service;tendency to stabilization of the horizontal displacements in a relatively short period of service; change, during service, of the position of the line passing through the points of the reinforcements where maximum strains were recorded. The reinforced slope behaviour express the conservative design of Equilibrium Limit methods and encourage the research on new design methods for geosynthetic reinforced soil systems. 相似文献
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采用Mohr-Coulomb强度理论,对下有不透水层的无限边坡进行了弹塑性分析,探讨了降雨过程中坡面水平位移的变化规律,分析了边坡安全系数和滑坡前坡面水平位移的关系。数值分析表明,土坡的抗剪强度参数、初始应力状态和降雨强度对边坡的安全系数和水平位移都有很大影响,但初始应力状态对滑坡发生的时间没有影响,对于具有较小抗剪强度参数的边坡,如果降雨强度较大,则滑坡时的水平位移较小。 相似文献
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Lulu Zhang Fang Wu Yafei Zheng Lihong Chen Jie Zhang Xu Li 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(3):169-182
Multiple types of responses, such as displacements, ground water level, pore water pressures, water contents, etc., are usually measured in comprehensive monitoring programmes for rainfall-induced landslide prevention. In this study, a probabilistic calibration method for coupled hydro-mechanical modelling of slope stability is presented with integration of multiple types of measurements. A numerical example of a soil slope under rainfall infiltration is illustrated to compare the effects of single and multiple types of responses on parameter estimation and model calibration. The results show that the soil parameters can be estimated with less uncertainty and total uncertainty bounds are narrower with multiple types of responses than with a single type of response. Model calibration based on multiple types of responses can compromise different responses and hence the means and standard deviations of model error are the smallest. A feasible correlation coefficient between soil modulus and permeability can be obtained from model calibration with multiple types of responses and single type of response as long as the responses include displacement data. 相似文献
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针对淮北地区水土流失问题,利用野外人工模拟降雨试验,分析了不同雨强(40mm/h、60mm/h和80mm/h)和坡度(5°、10°和15°)条件下砂姜黑土和黄潮土产流产沙差异。结果表明:砂姜黑土初始产流时间长,产流总量小。坡面出现细沟时,砂姜黑土初始含沙量随时间变化有减小趋势,最终趋于稳定,而黄潮土含沙量呈波动变化;60mm/h、80mm/h雨强10°坡砂姜黑土产沙总量大于黄潮土,其他情况黄潮土产沙总量大于砂姜黑土,黄潮土土壤侵蚀严重。砂姜黑土表面细沟发育密度大,主要在坡面中下部,为相互连通的树枝状结构,而黄潮土表面细沟发育密度小,形成沟壑。两种土壤产流总量、产沙总量与坡度、雨强分别呈多元线性函数、多元幂函数关系,雨强对坡面产流产沙总量的影响大于坡度。 相似文献
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Sam Frydman 《Geomechanics and Geoengineering》2020,15(1):54-63
ABSTRACTA simplified approach is presented for estimating permanent displacements in slopes as a result of both vertical and horizontal seismic accelerations. A study of 52 earthquake records showed that the time difference between maximum horizontal and vertical accelerations varied between 0 and 10.3 s. The approach is illustrated for an earth dam embankment by analysing the effects of five of the above earthquake records. The approach combines a pseudo-static slope stability analysis for estimation of the critical (or yield) horizontal-vertical acceleration combinations, and a Newmark type displacement analysis. Guidelines are presented for conservative choice of soil strength parameters of saturated clays for use in the stability analysis. While permanent displacements of up to 40 cm were predicted without considering the vertical acceleration component, no additional displacement above 3.5 cm resulted when this component was included. The predicted additional displacement was consistently less than 10%, and in 50% of the analyses, vertical acceleration led to smaller predicted displacements. The simple approach may be applied in analysis for any slope using real earthquake records. Using existing, empirical expressions for permanent displacement, based only on horizontal accelerations, the effect of the vertical accelerations may be conservatively estimated by increasing the displacement by 10%. 相似文献
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Consoli Nilo Cesar Reginato Naiara da Costa Lopes Júnior Luizmar da Silva Rocha Marcelo Maia Faro Vítor Pereira Born Ricardo Bergan 《Geotechnical and Geological Engineering》2021,39(6):4295-4313
This paper describes the main features related to lateral displacements with depth after successive lateral loading–unloading cycles applied to the top of reinforced-concrete flexible bored piles embedded in naturally bonded residual soil. The bored piles under study have a cylindrical shape, with 0.40-m in diameter and 8.0-m in length. Both bored piles types (P1 and P2) include an embedded steel pipe section in their center as longitudinal steel reinforcements: pile type P1 has another 16 steel rods as steel reinforcement to concrete while pile type P2 has no further steel reinforcement. Pile type P1 has three times as much stiffness (EI) and four and a half times the plastic moment (My) than pile type P2. A similar load–displacement performance was observed at initial loads as for small displacements of both piles. At this initial loading stage, the response of the reinforced concrete piles is a function of the soil characteristics and of a linear elastic pile deformation. During this stage, piles can even be understood as probes for evaluating soil reactions. For larger horizontal displacements, after the concrete section starts undergoing large deformations, approaching the ultimate bending moment, pile behavior and consequently the load–displacement relation starts to diverge for both piles. For pile P1 the values of relevant lateral displacements are extended to about 2.5-m in depth, while for pile P2 lateral displacements are mostly constrained to about 2.0-m in depth. Measurements of horizontal displacements of pile P1 against depth recorded with a slope indicator show that, after unloading, lateral loads at distinct stages (small and near failure loads), exhibits a much higher elastic phase of the system response. An analytical fitting model of soil reaction is proposed based on the measured displacements from slope indicator. The integration of a continuous model proposed for the soil reaction agrees fairly well with the measured displacements up to moments close to plastic limit. Results of load–displacement show that the stiffer pile (P1) was able to mobilize twice as much lateral load compared to pile P2 for a service limit displacement of about 20 mm. The paper shows results that enable the isolation of the structural variable through real scale pile load tests, thus granting understanding of its importance and enabling its quantitative visualization in examples of piles embedded in residual soil sites.
相似文献8.
This paper presents probabilistic assessment of seismically-induced slope displacements considering uncertainties of seismic ground motions and soil properties.A stochastic ground motion model representing both the temporal and spectral non-stationarity of earthquake shakings and a three-dimensional rotational failure mechanism are integrated to assess Newmark-type slope displacements.A new probabilistic approach that incorporates machine learning in metamodeling technique is proposed,by combining relevance vector machine with polynomial chaos expansions(RVM-PCE).Compared with other PCE methods,the proposed RVM-PCE is shown to be more effective in estimating failure probabilities.The sensitivity and relative influence of each random input parameter to the slope displacements are discussed.Finally,the fragility curves for slope displacements are established for sitespecific soil conditions and earthquake hazard levels.The results indicate that the slope displacement is more sensitive to the intensities and strong shaking durations of seismic ground motions than the frequency contents,and a critical Arias intensity that leads to the maximum annual failure probabilities can be identified by the proposed approach. 相似文献
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Kinematic and static analysis of geotechnical problems using the DEM has been widely accepted in the research arena for many years; however, its routine use in geotechnical practice for slope stability analysis still remains limited. This study focuses on the behavior of cohesive soil slopes undergoing failure initiation and succedent run-out. The numerical simulations of a supposititious slope composed of homogeneous cohesive soil were conducted using the DEM. The cohesive soil was simulated using contact-bonded graded aggregates of diameters ranging from 80 to 160 mm. This study investigated the microcrack-growth, particle displacements, particle movement and porosity changes within the slope fill. The simulation results showed that the failure mechanism is a rotational one at the failure initiation stage and gradually transfer to a slide/flow mode as progressive failure occurs. The porosity of deposit mass increased remarkably as result of dilation and block void. The run-out behavior of failure mass is not very sensitive with the viscous damping constant. 相似文献
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Ming Lu 《Engineering Geology》1998,49(3-4):353-361
A three-dimensional finite element analysis was performed to simulate field tests at a pilot gas storage project. The storage was a shallow rock cavern lined with a 6 mm thick steel liner. During the tests, high internal pressure up to 52 MPa was applied and deformation of both rock mass and the steel liner was recorded. The maximum rock displacements of less than 6 mm was numerically predicted and fits the measurement very well. The three-dimensional nonlinear finite element modeling has confirmed the overall stability of the structure and revealed the functioning of each structural component, including the rock mass, concrete lining and the steel liner. 相似文献
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为探明坡面土壤侵蚀过程中细沟的演变规律,研究细沟形态特征量化方法是非常重要的。利用室内土槽模拟降雨试验,对比了45 mm/h、87 mm/h和127 mm/h雨强下容重分别为1.30 g/cm3和1.05 g/cm3两种黄土在20°陡坡坡面细沟发育形态的差异,并分别采用分形维数、拓扑参数对细沟沟网的形态特征进行量化描述,引入地貌信息熵理论进行坡面地貌信息熵计算,然后对各量化参数的敏感性进行了分析。结果表明,分形维数作为整体性的量化参数,对描述发育成熟的细沟形态差异不够灵敏;坡面地貌信息熵能够反映侵蚀过程中侵蚀程度的变化,对细沟发育程度的描述较为灵敏;细沟沟网的拓扑特征参数较好地体现了沟网内部结构的差异,可用于描述沟网内部结构特征的较灵敏参数。 相似文献
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探明强降雨下泥沙输移突增的关键特征因子及其临界条件对预防泥沙灾害及减少水土流失将起到至关重要的作用。选取典型的四川紫色土试验区鹤鸣观小流域为研究对象,采用数据分类统计对比分析方法,对试验站近10年降雨径流输沙资料进行分析,研究强降雨情况下次降雨量、降雨强度和降雨历时等对泥沙输移突增的影响,找出导致泥沙输移突增的关键特征因子及其临界条件。研究结果表明:四川紫色土区强降雨情况下泥沙输移突增的关键特征因子为次降雨量、降雨强度以及最大径流模数;同时各关键因子的临界值分别为降雨强度5.3 mm/h,次降雨量130 mm,以耕作方式为主的坡地最大径流模数临界值为6 000 dm3/（km2·s）,以种植林草为主的坡地最大径流模数临界值为3 000 dm3/（km2·s）。 相似文献
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重庆溶洼—丘峰区土地利用类型对土壤抗蚀性的影响 总被引：1，自引：0，他引：1
以重庆鸡公山耕地、果园、撂荒地、灌草坡和林地5种土地利用类型为研究对象,通过野外采样调查与室内分析,采用主成分分析法对与土壤抗蚀性密切相关的11个常用指标进行筛选和综合评价,探讨不同土地利用类型下土壤抗蚀性能的变化状况和差异性。结果表明:研究区表征土壤抗侵蚀能力最优指标为:>0.25 mm团聚体破坏率、>0.25 mm水稳性团聚体含量、团聚度、<0.01 mm物理性黏粒含量、结构性颗粒指数和<0.001 mm黏粒含量。依据提炼出的3个主成分,建立土壤抗蚀性综合评价模型,即Y（综合指数）=0.712Y1+0.157Y2+0.131Y3,由此计算出土壤抗蚀性由强到弱为:林地> 灌草坡>撂荒地>果园>耕地。建议区内适当退耕还林还草,减少人为扰动,以利于提高土壤的抗蚀性能和水土保持能力。 相似文献
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黄土地层中的CaCO3与环境 总被引：20，自引：1，他引：20
本文根据大量观察分析,对黄土地层中的CaCO3含量、存在形式、淀积深度进行了研究,并进行了分类。结果表明,不仅CaCO3含量能够反映气候变化,而且其存在形式和淀积深度同样能反映气候变化;其淀积深度很少受时间影响,比含量更能可靠地用于气候研究。 相似文献
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对长江流域443个GNIP的降水样品同位素原始资料,分降雪和降雨进行δ2H和δ18O线性回归,得到降雪样品的相关方程为δ2H=7.965δ18O+17.114,有最大的斜率和截距;而降雨样品根据降水量大小从<10mm至>300mm分为4组后,得到的相关方程随着降水量的减小,斜率和截距均减小,斜率从7.701减小为5.705,截距从7.812×10-3减小为-5.479×10-3。δ2H~δ18O相关方程的斜率及截距与气温、水汽压之间的关系表明,在降水从云层底部降落到地面的过程中,仅较小降雨事件有明显的二次蒸发现象,并伴随着同位素的分馏。长江流域较小降雨事件占有比例很小,仅为所有降水事件的6.32%,所以二次蒸发效应仅引起地区大气降水方程斜率和截距的微弱减小。研究表明,单个降水原始资料的同位素分析,能产生长期加权平均降水同位素分析得不到的宝贵信息。 相似文献
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《Engineering Geology》2000,57(3-4):179-192
Long-term in situ monitoring of slow tectonic movements has been applied to a seismoactive region of SW Bulgaria, within the epicentral zone of one of the strongest earthquakes in Europe (4 April 1904, M=7.8). The region has been found the most seismoactive in Bulgaria being of interest to many scientists. Three spatial extensometers were installed here in carefully selected sites to reflect fault movements on fissures. The extensometer TM-71 used here, enables three-dimensional detecting of even very slow movements with the accuracy of 0.01 mm and high stability over time. After 17 years of measuring, the rates of tectonic movements were established at all three monitoring points. Movements recorded at point B6 located in the seismoactive Kroupnik fault zone are of a relatively high rate. Locally, they show left-lateral strike–slips at rates of ca. 2.7 mm year−1, as well as thrusting with a mean rate of 1.9 mm year−1. Monitoring point K7 located in a fissure of the same zone on a steep slope affected by recent earthquakes has shown an uplift tendency of the block W of the Strouma Fault, with a result of gradual slope subsidence occurring from time to time. Monitoring point K5 located in a fissure of Strouma Fault zone became increasingly active during the last 2 years after 8 years of relative quiescence. Before that, only low left-lateral movements could be observed. Long-term fissure monitoring has shown quite a number of details interpretable to the dynamics of a broad region. Permanent shear displacements were found to develop after earthquakes. It was established that only a certain distinct part of local earthquakes provide such a displacement reaction at the monitoring points showing particular seismic connections. 相似文献
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随着我国城市化进程的不断推进,地下空间的开发和利用越来越受重视,特别是盾构隧道已成为工程建设的重要技术手段。而城市地下环境日趋复杂,市政隧道下穿既有道路的项目愈发常见,研究与之对应的土体位移预测方法对地下空间安全评估至关重要。借助弹性力学中薄壁圆筒的平面模型,构建相应的边界条件,推导出适用于有重地层浅埋圆截面土体沉降变形计算方法。以澳门纯钢纤维混凝土盾构隧道下穿友谊大马路工程为实例,并与不同收敛模式下随机介质理论进行对比验证。研究结果表明：理论公式与土体位移实测值吻合度较高,且略优于随机介质理论的计算结果。理论公式综合考虑了路基土体参数、隧道深径比及施工技术水平等因素的影响,计算结果合理可靠,可为盾构隧道下穿施工诱发土体位移预测提供重要的理论支持。 相似文献
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滑坡位移的多模态支持向量机模型预测 总被引：1，自引：0，他引：1
将支持向量机（support vector machine,SVM）方法与信号分析中的经验模态分解（empirical mode decomposition, EMD）方法相匹配,提出了一种通过多模态支持向量机函数回归分析建模预测滑坡位移的理论方法。以边坡位移历史观测数据为基础,应用EMD方法获得滑坡形成过程中位移演化的几个特征时间模态,构成了多模态信息统计学习样本,确定了边坡位移演化的自适应多尺度变化信息。对应于每个经验模态的位移变化信息,引入了多模态SVM建模方法,然后合成不同经验模态下边坡位移的计算结果,得到滑坡位移的预测值。以卧龙寺新滑坡和新滩滑坡的监测数据为基础的理论预测结果表明,与采用遗传算法的神经网络方法的预测结果相比,支持向量机经验模态方法具有更强的预测能力,理论预测结果与实际监测值具有很好的一致性 相似文献