静力触探判别饱和砂性土液化公式的探讨

目前国内有许多工程勘察单位利用静力触探建立了本地区的饱和砂性土的液化判别公式,本文通过利用静力触探在淮阴市区进行工程地质勘察的实际资料,经数理统计计算后,建立了本地区的静力触探判别饱和砂性土液化的公式。现状液化是一种宏观震害现象。目前国内外评价砂土液化可能性的方法基本上可分两大类:剪应力比较法。即将计算的场地地震剪     

双桥静力触探在尾矿坝勘查中的技术应用

静力触探试验适用于软土、一般粘性土、粉土、砂土和含少量碎石的土,作为一种轻便、快捷、高效的原位测试技术,在岩土工程勘察、检测等方面得到了广泛应用。目前由于各地对静力触探经验技术和数据积累的不同,在我国对静力触探试验结果褒贬不一。本文通过双桥静力触探在尾矿坝勘察中的具体应用,以及静力触探成果的具体分析与评价,体现了静力触探在尾矿坝勘察中的适用性和重要性。     

初析静力触探判别液化对标准贯入试验的优越性

结合7个勘察场地的标准贯入和静力触探原位测试数据,应用数理统计原理和方法对二者进行比较分析,得出用静力触探试验判别地基土液化的均方差和变异系数等均优越于标准贯入试验。     

基于双桥静力触探的饱和砂土液化判别方法刍议

饱和砂土液化是地震引发地基变形失稳、建筑受损破坏的主因之一,合理判定液化可能性是勘察实践和理论研究的重大课题。国内规范要求砂土液化判别仍以标准贯入试验为主,静力触探等原位测试方法为辅,静力触探较其他原位测试手段,在操作便利性、数据采集连续性、测试成本和抗干扰能力等方面更具优势。针对国内规范常用静力触探砂土液化判别方法进行了分析研究,并结合勘察实例进行了计算和对比,探讨了静力触探判别液化方法的土层适用性,并提出有关改进建议。     

静力触探在工程地质勘察中的应用

静力触探是工程地质勘察中一项比较先进的原位测试手段,本文通过双桥探头所反映的曲线图形来解决一些工程地质问题,正确评价地基土的性质。     

邯郸市饱和粉土地震液化判别与差异分析

采用标准贯入试验法、静力触探法及宏观判别法对邯郸市某工程粉土地基进行了液化判别,并对判别结果进行对比分析。根据判别方法所考虑的因素和特点,结合粉土的区域特征,提出了适合邯郸市饱和粉土的综合判别方法,从而提高了液化判别的可靠性。     

液化判别中基于人工神经网络的粘粒含量取值研究

岩土工程勘察实践中,得到正确的粘粒含量是进行液化判别的前提与基础。利用静力触探成果进行液化判别时,粘粒含量往往采用场地平均值或邻近钻孔相应深度处土样的粘粒含量值,与判别点处粘粒含量实际值间存在一定差别,影响了采用静力触探液化判别的准确性。采用人工神经网络可建立起需液化判别土层各点粘粒含量与相应空间坐标间的关系,从而得到场地内需液化判别土层粘粒含量的分布规律,为液化判别提供更为准确的粘粒含量。     

几种地震液化判别方法的对比

地震液化判别是地震地质灾害评价的重要环节,不同的判别方法有时会得出不同的结论。对几种主要判别方法进行梳理,通过具体工程测试数据,分别应用标准贯入法、NCEER法、静力触探法及剪切波速法进行判别,分析各种方法的结论,得出用剪切波速法进行液化判别存在明显的缺陷,对于浅层的粉土较为冒进,对于深层的砂土又过于保守。标准贯入法、NCEER法、静力触探法得出的结论基本一致,但对于细颗粒含量较高的砂土,NCEER法与其他方法存在明显的差别。     

静力触探在工程地质勘察中的应用

本文依据多年来工程地质勘察成果,详细介绍了静力触探应用于地层划分;确定地基土容许承载力;预估单桩竖向承载力;判别在地震动力作用下砂土液化势;地基土空洞探测;确定湿陷性黄土浸水湿陷事故范围;活动断层的工程软弱带的分布与走向。     

基于台湾集集地震数据的CPT与SPT液化判别方法比较

利用集集地震静力触探试验(CPT)数据,对基于CPT测试的Robertson液化判别方法和Olsen方法进行了检验,两个方法对液化点判别成功率分别为82.61%和80.43%,对非液化点判别成功率分别为31.82%和44.32%。CPT液化判别方法对液化点判别基本可靠,但对非液化点判别准确性较差。对集集地震标准贯入试验(SPT)数据,美国地震工程研究中心(NCEER)推荐的SPT液化判别方法对液化点和非液化点判别成功率分别达到92.41%和94.35%。SPT方法判别成功率非常高,整体准确性远高于CPT方法。另一方面,CPT的土分类图可以同时反映土的种类与强度,甚至可以对集集地震液化土与非液化土进行区分。对于细粒土的液化初判,CPT土分类图也优于SPT方法中的黏粒含量指标。因此,土分类图是CPT的优势所在。     

安哥拉格埃路砂地层的承载力研究

安哥拉格埃路地层（Quelo）棕红色砂土形成年代较长,低含水率下地基承载力较高,但遇水后地基承载力降低幅度较大,地基处理方案常有争议。大量的工程实践和专项研究表明,地基土的承载力与含水率有明显的相关性,通过探井取样和原位测试,查明了地基土的物理力学特性,分析不同含水率条件下的静力触探试验(CPT)和平板载荷试验(PLT)数据,建立了适用于该地层的地基承载力与含水率的幂函数关系式以及地基承载力与锥头阻力的线性经验公式。静力触探试验结果表明,地层锥头阻力qc和侧壁摩阻力fs随深度增加而逐渐提高,土质均匀,但摩阻比Rf较小。分析认为,采用不经碾压的砂土作为地基,具有较高的风险;对于多层及9～13层建筑的地基处理,采用换填垫层法较桩基更合理。     

Field measurements of shear strength of an underconsolidated marine clay

This paper presents the observations of cone penetration testing (CPT), in situ vane shear testing and undrained triaxial testing of underconsolidated marine clay in the Craney Island Dredged Material Management Area (CIDMMA), Norfolk, VA. Comparison of vane shear measurements, taken during 1981–1983, to CPT measurements, taken during 1993, indicates a change in undrained shear strength. Both the vane shear and cone penetration resistances are lowest at the mid-heights of the clay layers and the excess pore water pressures are highest at the mid-height of the clay layers, indicating that the clay layer is underconsolidated.     

A performance-based framework for assessing liquefaction potential based on CPT data

This article describes a new performance-based approach for evaluating the return period of seismic soil liquefaction based on standard penetration test (SPT) and cone penetration test (CPT) data. The conventional liquefaction evaluation methods consider a single acceleration level and magnitude and these approaches fail to take into account the uncertainty in earthquake loading. The seismic hazard analysis based on the probabilistic method clearly shows that a particular acceleration value is being contributed by different magnitudes with varying probability. In the new method presented in this article, the entire range of ground shaking and the entire range of earthquake magnitude are considered and the liquefaction return period is evaluated based on the SPT and CPT data. This article explains the performance-based methodology for the liquefaction analysis – starting from probabilistic seismic hazard analysis (PSHA) for the evaluation of seismic hazard and the performance-based method to evaluate the liquefaction return period. A case study has been done for Bangalore, India, based on SPT data and converted CPT values. The comparison of results obtained from both the methods have been presented. In an area of 220 km² in Bangalore city, the site class was assessed based on large number of borehole data and 58 Multi-channel analysis of surface wave survey. Using the site class and peak acceleration at rock depth from PSHA, the peak ground acceleration at the ground surface was estimated using probabilistic approach. The liquefaction analysis was done based on 450 borehole data obtained in the study area. The results of CPT match well with the results obtained from similar analysis with SPT data.     

震动液化间接测试技术在吉林西部砂土地层中的应用

鉴于目前常用的剪切波速测试法、液性指数法和原位测试法等进行砂土震动液化的复判方法存在弊端,本文提出标准贯入击数--锥尖阻力复判法( qc--N 复判法) 及瑞利波法等间接测试击数的方法进行砂土震动液化判别。通过理论计算及实例验证表明,判别结果与相对密度法测得结果一致,同时具有工作效率高、生产成本低的优点,有较高的实际应用价值。     

Support vector machines‐based modelling of seismic liquefaction potential

This paper investigates the potential of support vector machines (SVM)‐based classification approach to assess the liquefaction potential from actual standard penetration test (SPT) and cone penetration test (CPT) field data. SVMs are based on statistical learning theory and found to work well in comparison to neural networks in several other applications. Both CPT and SPT field data sets is used with SVMs for predicting the occurrence and non‐occurrence of liquefaction based on different input parameter combination. With SPT and CPT test data sets, highest accuracy of 96 and 97%, respectively, was achieved with SVMs. This suggests that SVMs can effectively be used to model the complex relationship between different soil parameter and the liquefaction potential. Several other combinations of input variable were used to assess the influence of different input parameters on liquefaction potential. Proposed approach suggest that neither normalized cone resistance value with CPT data nor the calculation of standardized SPT value is required with SPT data. Further, SVMs required few user‐defined parameters and provide better performance in comparison to neural network approach. Copyright © 2006 John Wiley & Sons, Ltd.     

长春硬塑状态老黏性土地基承载力

为提供长春硬塑状态老黏性土可靠的地基承载力依据,探讨适宜的确定地基承载力的方法,采用载荷试验、静力触探试验原位测试和室内土工试验等方法对长春老黏性土进行了测试研究,获取了地基承载力特征值（306~425 kPa）、静力触探锥尖阻力（1.9~3.3 MPa）、天然孔隙比(0.63~0.72)和液性指数(0.02~0.25)等试验数据。通过对试验数据的统计分析,得出地基承载力特征值与静力触探锥尖阻力线性相关,并与天然孔隙比和液性指数线性相关的结论。据此,提出了根据静力触探锥尖阻力计算长春老黏性土地基承载力特征值的经验公式,总结出根据室内土工试验指标确定长春老黏性土地基承载力特征值的数据表。     

基于静力触探试验的液化判别新方法

近来地震液化灾害频发,再次成为研究重点,发展具有良好应用前景的基于静力触探试验（CPT）的液化判别方法对预防液化灾害具有重要意义。以Boulanger数据库171组数据为回归样本,分析既有方法存在的问题,提出了基于CPT液化判别的双曲线模型和计算公式,并通过提取2011年新西兰地震147组液化新数据,对该方法进行对比检验。研究表明,我国岩土工程勘察规范的CPT液化判别方法对浅埋砂层偏于保守,对深层土又明显偏于危险,而国际上具有代表性的Robertson方法,其液化临界线存在低烈度区不合理回弯、高烈度区又偏于保守的问题。提出的新公式在不同地震动强度和砂层埋深下均可给出合理判别结果,克服了国内外既有方法的缺点,并纳入到具有样板规范性质的《建筑工程抗震性态设计通则》修订稿中,可为我国相关规范修订和工程应用提供支持。