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软土地基处理的主要目的之一是尽量增加地基施工沉降和减少工后沉降,如何改进软基沉降处理的工程措施及如何准确地预测软基沉降成为关键问题,对软基沉降计算方法的研究也越来越引起重视。收集了珠海海相软土地基6个排水固结法软基处理工程实例,对分层总和法沉降计算公式进行修正。 相似文献
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对济南地区基坑降水引起既有地基沉降的认识 总被引:3,自引:0,他引:3
结合工程经验,对基坑降水引起的周边既有建筑地基沉降的影响因素进行了总结,针对采用分层总和法估算降水引起地基沉降公式中,对应附加应力段的压缩系数取值不准问题,提出了采用基于地层应力历史的降水引起周边地基沉降的估算方法,并结合工程实例对降水引起地基沉降进行了预测。 相似文献
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小波分析和RBF神经网络在地基沉降预测中的应用研究 总被引:4,自引:2,他引:2
地基沉降是一种危害很大的环境灾害。地基沉降的监测数据经常受降雨及工程施工等诸多外界因素的干扰,故而在沉降曲线中存在许多数据突变点。为此,提出基于小波分析与RBF神经网络相结合的新的地基沉降预测方法,首先采用小波分析对对原始监测数据进行数据去噪处理,进而得到反映实际变化的地基沉降曲线,然后采用径向基函数(RBF)神经网络方法对其进行预测,为工程设计提供依据。最后结合工程实例分析,通过多种小波去噪与预测结果的对比研究,表明3次B样条小波的去噪及预测效果最好,与实测值能较好地吻合,具有较好的工程应用前景。 相似文献
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堆山工程是为了有效处理固体废弃物,进行生态城市建设中一种新的工程类型,人工山体地基沉降量是评价其稳定性非常重要的指标。本文采用固结理论与分层总和法分别计算出人工山体地基堆载竣工时与最终的沉降量,并对关键位置地基土体的固结度特征进行了分析,得到了沉降变形、固结度随时间的变化规律。将实测结果与计算结果进行了对比分析,二者基本一致,表明采用这一理论方法可以有效预测人工堆山体地基沉降。 相似文献
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为了提高软土地基沉降模型的拟合精度,通过对实测数据的分析,研究了软土地基沉降发展规律。在前人研究的基础上将Logistic预测模型和Gompertz预测模型进行叠加,建立了地基沉降历时曲线的Logistic-Gompertz叠加曲线模型,并给出模型的求解方式。通过工程实例讨论了新模型的拟合效果,对比计算结果表明所建立的新模型拟合精度不仅比Logistic模型和Gompertz模型要高,而且可靠性也优于各个单一的模型。新模型具有一定的科学性和适用性,是一种分析地基沉降观测资料的有效方法。 相似文献
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FLAC有限差分在地基沉降计算中的应用 总被引:3,自引:0,他引:3
介绍了有限差分法计算软件FLAC以及该软件在计算地基沉降时的步骤。通过对一个实际工程的计算对比,发现FLAC和分层总和法这两种方法计算得到的地基沉降量结果之间的误差仅为1.2mm,满足地基设计的要求,且FLAC有限差分法计算地基沉降量具有较好的准确性、直观性和简便性。 相似文献
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采用Asaoka法对深圳某工程实例的地基工后沉降进行预测,发现选取不同的起始点和时间间隔时,其预测结果相差有3倍之多。因此,用数学方法对预测地基沉降的Asaoka法的表达式进行分析,探讨其拟合参数的误差对沉降预测结果的影响,提出了拟合参数误差放大系数的概念,并对预测结果的可靠性进行分析和评估。分析结果表明:影响Asaoka法沉降预测结果稳定性的一个主要原因是其预测沉降的表达式对拟合参数β_1过于敏感,而且敏感性随着β_1的增大而增大,因此,在保证线性拟合良好的前提下,增大离散点的时间间隔,可减小β_1,从而有效减轻β_1的误差对预测结果的影响;采用Asaoka法预测沉降时,不能单凭线性拟合的好坏来判断一个预测结果的可靠性,还需要考虑拟合参数的误差放大系数的大小。 相似文献
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三次样条插值曲线在Asaoka法中的应用 总被引:6,自引:0,他引:6
在软土地基上修筑高等级公路,能否确保工程按期保质完成,关键之一在于能否正确估算地基沉降量。利用已有的沉降观测资料来预测未来的沉降,Asaoka方法就是较早提出的一种,它不仅简单易用而且有一定的理论基础,使得该方法与目前国内常用的经验曲线配合法有着本质的区别,这也是它今天能够吸引众多学者研究的原因。对Asaoka从理论基础和沉降递推结果进行了分析,利用三次样条插值曲线来处理非等时间间隔的沉降观测资料,结果表明,这种处理方法是可行的。 相似文献
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Motohei Kanayama Alexander Rohe Leon A. van Paassen 《Geotechnical and Geological Engineering》2014,32(3):687-697
Earth-fill structures such as embankments, which are constructed for the preservation of land and infrastructure, show significant amount of settlement during and after construction in lowland areas with soft grounds. Settlements are often still predicted with large uncertainty and frequently observational methods are applied using settlement monitoring results in the early stage after construction to predict the long term settlement. Most of these methods require a significant amount of measurements to enable accurate predictions. In this paper, an artificial neural network model for settlement prediction is evaluated and improved using measurement records from a test embankment in The Netherlands. Based on a learning pattern that focuses on convergence of the settlement rate, the basic model predicted settlements which were in good agreement with the measurements, when the amount of measured data used as teach data for the model exceeded a degree of consolidation of 69 %. For lower amounts of teach data the accuracy of settlement prediction was limited. To improve the accuracy of settlement prediction, it is proposed to add short-term predicted values that satisfy predefined statistical criteria of low coefficient of variance or low standard deviation to the teach data, after which the model is allowed to relearn and repredict the settlement. This procedure is repeated until all predicted values satisfy the criterion. Using the improved network model resulted in significantly better predictions. Predicted settlements were in good agreement with the measurements, even when only the measurements up to a consolidation stage of 35 % were used as initial teach data. 相似文献
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铁路客运专线路基沉降预测的新方法 总被引:3,自引:0,他引:3
路基的工后沉降控制是高速铁路建设的重要问题之一,利用铁路客运专线路基现场观测数据,找出相应的路基沉降规律有利于指导设计与施工。在分析武广铁路客运专线路基大量数据的基础上,将三点法的基本思想引入到双曲线模型,建立了基于双曲线模型的三点法。其具体做法是:在实测沉降曲线上选取3个适当的点作为预测样本,代入双曲线模型进行预测。为了检验新方法,运用常用的双曲线方法、三点法、Asaoka法、星野法、泊松曲线法进行对比分析,并且提出了新方法的取点控制条件。研究表明:基于双曲线模型的三点法的预测误差小、相关系数高、与实测数据吻合较好,具有一定的实用价值,为铁路客运专线无砟轨道铺设的沉降预测问题提供了参考。 相似文献
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软土路基后期沉降推算方法及误差分析 总被引:6,自引:1,他引:5
以某高速公路软基处理断面实测沉降资料为基础,分别对应用较为广泛的7种后期沉降推算方法的精度及误差进行了比较分析。针对每一种推算方法,研究了计算时间起点和时间跨度对推算精度的影响,并探讨了各种方法的优缺点及适用性。研究表明,常用的双曲线法和指数曲线法的推算精度与推算的时间起点关系较大,建议以恒载期3~5个月后为时间起点,取较长时间的沉降资料进行推算,可有效提高推算精度;三点法、沉降速率法和新野法的推算精度较高,且与计算时间起点和时间跨度的关系不大,但都需要对原始观测数据进行特殊处理,计算较为复杂;Asaoka法的推算结果与实测值最为接近,其缺点在于无法对停止加载后某阶段的沉降进行推求。 相似文献
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Factors Affecting Consolidation Related Prediction of Singapore Marine Clay by Observational Methods
The use of prefabricated vertical drains with preloading option is the most widely-used ground improvement method for the
improvement of marine clays in land reclamation projects. The assessment of the degree of consolidation of the marine clay
is of paramount importance prior to the removal of preload in such ground improvement projects. This analysis can be carried
out by means of observational methods with the use of field settlement plates and piezometer monitoring. Field settlement
monitoring data can be used to ascertain the settlement of the reclaimed fill from the time of initial installation. The field
settlement data can be analysed by the Asaoka method to predict the ultimate settlement of the reclaimed land under the surcharge
fill. Back-analysis of the field settlement data will enable the coefficient of consolidation due to horizontal flow to be
closely estimated. Piezometer monitoring data can be analysed to obtain the degree of consolidation of the improved marine
clay. Back-analysis of the piezometer data will also enable the coefficient of consolidation due to horizontal flow to be
estimated. The aim of this paper is to highlight the significance and impact of the various factors that affect prediction
by the Asaoka and piezometer assessment methods. The authors findings of the Asaoka method reveal that the magnitude of ultimate
settlement decreases and the degree of consolidation subsequently increases as a longer period of assessment is used in the
prediction. The degree of consolidation predicted by the piezometers is found to be in good agreement with the Asaoka method
for the early period of assessment. However as the assessment period increases, the piezometer indicates lower degree of consolidation
as compared to field settlement predictions. 相似文献
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根据太湖地区某高速公路路基沉降实测资料,通过现场原位取样结合室内试验,分析了太湖冲湖积相软土的压缩特性,总结出软土路基的沉降变化规律,研究了工程地质条件和填土高度对路基沉降的影响,并采用归一化指标得到不同地基处理方式下的沉降估算公式,同时对两种常用全过程路基沉降预测方法进行了比较。结果表明,太湖冲湖积相软土具有较强的结构性;相似地质条件下的路基沉降差异较大,土体结构性是影响路基沉降的重要因素之一;归一化指标分析可得到不同路基处理方式下的简单沉降估算式;常用的全过程沉降量预测方法对于最终沉降量的预测均存在一定的偏差,可综合分析预测结果得到较为准确的预测值。 相似文献
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Numerous approaches exist for the prediction of the settlement improvement offered by the vibro-replacement technique in weak or marginal soil deposits. The majority of the settlement prediction methods are based on the unit cell assumption, with a small number based on plane strain or homogenisation techniques. In this paper, a comprehensive review and assessment of the more popular settlement prediction methods is carried out with a view to establishing which method(s) is/are in best agreement with finite element predictions from a series of PLAXIS 2D axisymmetric analyses on an end-bearing column. The Hardening Soil Model in PLAXIS 2D has been used to model the behaviour of both the granular column material and the treated soft clay soil. This study has shown that purely elastic settlement prediction methods overestimate the settlement improvement for large modular ratios, while the methods based on elastic–plastic theory are in better agreement with finite element predictions at higher modular ratios. In addition, a parameter sensitivity study has been carried out to establish the influence of a range of different design parameters on predictions obtained using a selection of elastic–plastic methods. 相似文献
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基于Weibull曲线的软基沉降预测模型分析 总被引:2,自引:0,他引:2
结合软基沉降机理,提出用Weibull模型预测软基沉降全过程。该预测模型参数意义较为明确,可以反映加载速度等因素的影响,克服了其它两种成长模型反弯点处沉降值与最终沉降相对不变的缺点。在利用其它模型预测时,只有初步判断实测样本反弯点的位置才能较科学的选择有效样本和相应模型进行预测。Weibull模型可以充分利用沉降观测样本,具有广泛的适应性,指数模型是它的一种退化形式。它不但可以预测线性加载的软基沉降,而且可以预测一次加载或近似一次加载的软基沉降。工程实例的实测和计算比较说明该模型是可靠的。 相似文献