土钉支护结构水平位移安全监控模型研究

【作者】 杨海荣；

【导师】 陈淮；

【作者基本信息】 郑州大学 ， 结构工程， 2004， 硕士

【摘要】 土钉支护技术已经成为国内深基坑工程的主要支护形式，保障土钉支护结构安全可靠的根本措施是进行施工过程中的变形监测。目前，国内现行规范规程提出的以极限变形值作为土钉支护结构水平位移的安全监测报警限值，是“结果控制”，在实际工程应用中具有一定的局限性。针对这种情况，本文提出了土钉支护结构水平位移安全监测“过程控制”的理念，旨在建立“土钉支护结构水平位移安全监控模型”，以“安全时程曲线”为控制依据，使土钉支护结构施工过程中的水平位移发展始终处在“安全时程曲线”之下，以确保最终变形在某一规定的阈值之内，用现有水平位移监测结果为施工方案的调整提供决策依据，从而对土钉支护结构施工全过程做到安全有效地监测和控制。 本论文主要开展了以下几个方面的工作： (1)分析研究了土钉支护结构水平位移预测的主要方法，包括：时间序列分析法、人工神经网络法、灰色预测法、失败树分析法和进化支持向量机法等，认为这些预测模型具有各自的适用性，但其根本思想多偏重于“预测”而非“安全控制”，这些方法多为理论推演，某些预测模型过于繁琐，在实际工程中不易推广应用。 (2)分析研究了大量国内深基坑工程土钉支护结构水平位移实际变形监测数据，并选择不同地域、不同岩性条件、不同施工方式的典型土钉支护工程12例，将其施工过程中现场监测的水平位移数据作为试验点绘在位移——时间坐标系中，根据这些点的分布或由这些点连成曲线的发展趋势，得出其水平位移时程曲线图，对支护结构水平位移发展规律进行了研究，明确了水平位移时程曲线的近似型态。 (3)分析了双曲函数、指数函数、对数函数等与土钉支护结构位移时程曲线相似的常见函数曲线，并最终选定了S形曲线和反正切函数作为拟合水平位移发展的时程模型。研究表明，采用S形曲线拟合土钉支护结构的水平位移时程曲线，得到回归参数a、b，虽然回归参数a、b具有很高的线性相关系数，但S形曲线从总体上说具有很陡的“突变”特征，不适合用于支护结构的安全监控。采用反正切函数拟合土钉支护结构的水平位移时程曲线，可以使其位移时程曲线与实测曲线最大限度地接近，从而确定了以反正切函数作为“安全时程曲线”，建立了土钉支护结构水平位移安全监控模型。 (4)用水平位移安全监控模型对12例典型土钉支护工程进行验证，用具体参数代入本文模型公式，绘制其安全时程曲线，与实测水平位移曲线进行比较，证明两者形状及发展趋势是一致的。杨海荣:土钉支护结构水平位移安全监控模型研究 (5)工程应用。将本文研究得出的土钉支护结构水平位移安全监控模型应用于郑州市的2个新建工程，将具体参数代入模型公式，事前绘出该具体工程的土钉支护结构水平位移安全时程曲线，作为土钉支护结构施工过程的控制依据。将施工过程中实测的水平位移数据及时绘出，并与安全时程曲线进行对比，当发现实测数据超出安全时程曲线时，立即向施工方报警。实际应用结果表明:“土钉支护结构水平位移安全监控模型”可以有效地应用于土钉支护结构水平位移安全监控。 本文研究取得了如下成果: (l)本文提出了“过程控制”思想并建立了“土钉支护结构水平位移安全监控模型”，以土钉支护结构变形发展的“安全时程曲线”为控制依据，使施工过程中的结构水平变形发展始终处在“安全时程曲线”之下，以确保土钉支护结构最终变形在某一规定的阂值之内，从而对施工过程进行全程有效地控制。 (2)对土钉支护结构水平位移发展规律进行了研究，认为:基坑坡顶水平位移随施工日期的延续而增大，基坑每一层开挖均产生一个水平位移，支护施工完成后水平位移逐渐趋于稳定。采用复合土钉支护结构的坡顶水平位移在整个施工过程表现为:浅层和深层土钉施工引起的水平位移增量相近，其绝对值较小;中层土钉施工水平位移增量最大。采用普通土钉支护结构坡顶水平位移在整个施工过程中呈加速增长趋势，随着每层的开挖，水平位移增量逐渐增大，深层开挖的水平位移增量约为浅层开挖的水平位移增量的2一3倍。基坑边壁中间观测点的水平位移大，靠近角部的水平位移较小。 (3)当采用S形曲线拟合土钉支护结构的水平位移时程时，尽管回归参数a，b时具有很高的线性相关性，但S形曲线从总体上说具有很陡的“突变”特征，不适合用于土钉’支护结构的安全监控。采用反正切函数作为“安全时程曲线”模型，则可以通过参数变换的方式，使位移时程曲线与实测曲线最大限度地接近;并且，可以根据工程实际条件，确定最大位移的具体数值，使本文模型公式具有可推广性。 (4)本文研究得出的土钉支护结构水平位移安全监控模型为::D(t卜制ar.ctg(击一l0)+fl式中，t一自降水开始计算的施工进程(d);D~一土钉支护结构的最终变形，可以根据工程地质情况、地下水位、地面堆载等情况综合确定，当无工程经验时可以取为(1%0一3%。)H，并在最初几排土钉施工完成取得实测数据后进行适当修正，其中H一开挖深度;T一变形稳定总时间，可以取人工降低地下水位至开挖到基坑底面时间另加10d。更多还原

【Abstract】 The soil nailing foundation pit retaining structure (SONFOPIRS) has become the mainstream in the domestic deep foundation pit retaining construction. In order to ensure the construction safety, the security monitoring must be ensured entirely through the construction course. In the active national code, the accumulated horizontal displacement is used as the SONFOPIRS security monitoring alarming criteria, which is the Result Control Methodology and has the limitation in the practical applications. Aiming at this, the SONFOPIRS horizontal displacement development security monitoring Trace-Control Methodology and the SONFOPIRS horizontal displacement development security-monitoring model is set up in this dissertation. According to the methodology, the SONFOPIRS horizontal displacement development is limited in the security trace-control curve from beginning to end, so that the accumulated horizontal displacement is controlled in one threshold parameter. As the decision-making basis of the construction project, the existing horizontal displacement monitoring result can be used to monitor and control the SONFOPIRS construction course effectively.The dissertation completes the following works:(1) Some horizontal displacement forecast theories on the SONFOPIRS have been analyzed and studied including the time-sequence analysis, the Artificial Neural Network, the Gray Color Forecast, the Failure Cause Tree Analysis and so on, and then such conclusions are given: these forecast models have their applicability respectively, however, they mainly focus on "forecast" instead of "security control", and the study methods centralize in rationalism deduce, and some forecast models are so complex that not easily to spread and apply.(2) A great deal of projects’ deformation field survey data have been analyzed, and a dozen of typical project cases’ horizontal displacement development rules have been studied with various sites, lithology and dialect construction procedures: the field survey horizontal displacement data in the construction course are draw on the displacement-time coordinate system as the test points, with the distribution of these points or the developing trend of these points forming curves, their horizontal displacement-time curve can be concluded, and then the SONFOPIRS horizontal displacement development rule can be studied and its approximate shape of thedisplacement-time curve can be judged.(3) After trying on some functions such as the hyperbola, index and logarithm, finally, the S-shapecl and the arctan functions are confirmed as the fitting ones for horizontal displacement-time curve. The research indicates: When being used to fit the horizontal displacement-time curve, the S-shaped curve has an abrupt change feature as a whole, although the regression parameters a and b have the closest linearity relation, therefore it is not suitable to use as the security monitoring. With its displacement-time model closes the survey curve with maximum, the arctan function model can be determined as the security displacement-time curve.(4) The horizontal displacement security-monitoring model is validated in the dozen of typical project cases: the correlative parameters are applied in the model’s formula and draw their security displacement-time curve. After comparing with the survey curve, the security displacement-time curve is proved that its shape and development trend is consistent with the survey one.(5) Practical application: the SONFOPIRS security monitoring model is applied in two new building projects in Zhengzhou, the correlative parameters are applied in the model’s formula and draw their security displacement-time curve before surveying, which are used as the control criteria of the SONFOPIRS construction course. The surveying data in the construction course are draw on time and compared with the security displacement-time curve. The alarming is given to the construction while the surveying data exceeds the security displacement-time curve. The project application indicates that the S更多还原