Determination of the material damping ratio and the shear wave velocity with the Seismic Cone Penetration Test

The Seismic Cone Penetration Test (SCPT) is used to determine the variation with depth of the shear (and longitudinal) wave velocity at various sites in Belgium. The cross correlation technique together with a posteriori increase of the sampling frequency proves to be a reliable method to determine wave velocities by the SCPT. Additionally, the Spectral Ratio Slope (SRS) method is applied to Fourier transforms of the measured response to determine the variation of the material damping ratio with depth. This method is applied to synthetic signals computed for three different soil profiles with known characteristics and to the horizontal acceleration time histories that have been measured during SCPT on two sites. The influence of some signal processing techniques commonly applied in the SRS method is studied. A remarkable influence of the window length, applied on the predicted signals, on the computed material damping ratio is found, especially its scattering. It is therefore concluded that the use of a window function should be avoided wherever possible. On one of the two test sites, results of Resonant Column Tests and Free Torsion Pendulum Tests on undisturbed soil samples have been used to evaluate the values of the shear wave velocity and the material damping ratio as obtained in the in situ test.     

运用轻便触探和静载荷试验研究黄土的湿陷性(英文)

黄土在应力作用下迂水时力学强度迅速下降 ,产生大范围的快速沉陷。这就是黄土的湿陷性 ,是黄土的诸多特性之一。鉴于对黄土湿陷性以往用各种实验室试验指标进行评价 ,这里提出运用动力触探和静载荷试验进行黄土湿陷性原位评价的一种简便的新方法。该方法的试验程序是 ,先用轻便可变动能触探仪在天然状态和饱水状态下进行触探试验 ,而后在触探孔完成静载荷压缩性试验。运用中国黄土高原黄土原位动力触探和静载荷试验测得的资料 ,详细分析了天然状态的黄土对探头阻力 qdnat,饱水状态的黄土对探头阻力 qdsat,实验室测得的湿陷性指数s压缩曲线参数 (即触探极限压力 ppf,触探蠕变压力ppl 和触探载荷模量Epn)的关系。结果证明所提出的方法适用于原位判定黄土的湿陷性。     

利用qc,D50评价砂土地震液化势研究

本文根据国内外地震液化调查资料，建立了利用双桥静力触探锥头阻力ｑｃ和平均粒径Ｄ５０判别地震液化势的半经验性方法。这种方法对评价地震液化势是颇为有效的。     

锥状喀斯特区溶洞景观特征及其旅游资源评价

锥状喀斯特是湿热带地区重要的喀斯特地貌景观类型和高品位的旅游资源。发育在锥状喀斯特地区的溶洞既是锥状喀斯特地貌景观的重要组成部分,也是发展旅游不可替代的景观资源。本文从这一认识出发,首先揭示了锥状喀斯特及溶洞发育的四大特征: ( 1)溶洞成因类型多样; ( 2)是深、长、大洞的主要发育区;( 3)不同锥状喀斯特发育阶段,洞穴类型组合不同; ( 4)能形成溶蚀、沉积形态丰富、造型奇特、美学价值很高的溶洞景观集群。在此基础上,进行了初步的旅游价值评价,指出在旅游开发中具有三大资源优势: ( 1)洞穴资源具有多功能性(科研、探险、观光旅游、生态旅游、医疗等)。( 2)构成独特的高品位峰林— 溶洞(地面、地下)综合景观类型。( 3)景观资源的高度互补性可提高旅游景观内涵的丰度和旅游经济效益。      

Lyttelton Volcano, Banks Peninsula, New Zealand: Primary volcanic landforms and eruptive centre identification

Lyttelton Volcano, Banks Peninsula, New Zealand, has historically been viewed as a simple volcanic cone. This paper uses digital terrain models (DTM) and primary volcanic landforms to reinterpret Lyttelton Volcano as having multiple eruptive centres. Primary volcanic landforms are features produced during active volcanism, classified as constructional, hypabyssal, and erosional volcanic features. Constructional volcanic features are lava flows, scoria cones and domes; hypabyssal volcanic features are dykes and sills; and erosional volcanic features are valley and ridge patterns and orientations. Lava flow trends are recognised from aerial photograph analysis and supported by field observations, highlighting radiating lava trends around specific locations within Lyttelton Harbour. Scoria cones and domes occur on the outer flanks of volcanic cones, and are used as such in the identification of remnant cone surfaces. Dyke orientations are plotted and then projected to the interior of the volcano, defining 13 zones of convergence. The projected arrays of these orientations highlight defined regions along the erosional crater rim, each indicating a radial dyke swarm, from which the projected trends of the associated dykes indicate an eruptive centre. Valley and ridge orientations are projected from the longest valley or ridge segment, towards the inner harbour. Radiating erosive patterns are incepted during the growth and degradation of a volcanic cone, with the resulting trends orienting to the summit. Zones of convergence/eruptive centres are identified from lava flow orientations, onlapping lava sequences, scoria cones, and intrusive locations. The summit of a volcanic edifice can be identified from the orientations of valleys and ridges, while radial dyke systems determine whether this summit was a volcanic centre or simply a local topographic high. Volcanic landforms are used to identify cone sectors, the preserved sector associated with a particular eruptive centre. Cone sector limits are defined by a basal footprint and an erosional crater rim, with similar arcuate features (remnant cone features) being exposed in the interior of the volcano. Lyttelton Volcano comprises fifteen volcanic cones, with vent locations controlled by underlying fault lineaments. The growth and erosion of each volcanic cone is reflected in primary volcanic landforms, with the preserved features of cones confined to cone sectors and cone artefacts.     

Investigation of seismic behavior of fluid–rectangular tank–soil/foundation systems in frequency domain

Main purpose of this study is to evaluate the dynamic behavior of fluid–rectangular tank–soil/foundation system with a simple and fast seismic analysis procedure. In this procedure, interaction effects are presented by Housner's two mass approximations for fluid and the cone model for soil/foundation system. This approach can determine; displacement at the height of the impulsive mass, the sloshing displacement and base forces for the soil/foundation system conditions including embedment and incompressible soil cases. Models and equations for proposed method were briefly explained for different tank–soil/foundation system combinations. By means of changing soil/foundation conditions, some comparisons are made on base forces and sloshing responses for the cases of embedment and no embedment. The results showed that the displacements and base shear forces generally decreased, with decreasing soil stiffness. However, embedment, wall flexibility, and soil–structure interaction (SSI) did not considerably affect the sloshing displacement.     

Applicability of existing empirical shear wave velocity correlations to seismic cone penetration test data in Christchurch New Zealand

Seismic piezocone (SCPTu) data compiled from 86 sites in the greater Christchurch, New Zealand area are used to evaluate several existing empirical correlations for predicting shear wave velocity from cone penetration test (CPT) data. It is shown that all the considered prediction models are biased towards overestimation of the shear wave velocity of the Christchurch soil deposits, demonstrating the need for a Christchurch-specific shear wave velocity prediction model (McGann et al., 2014) [1]. It is hypothesized that the unique depositional environment of the considered soils and the potential loss of soil ageing effects brought about by the 2010–2011 Canterbury earthquake sequence are the primary source of the observed prediction bias.     

扁铲侧胀试验在滨海沉积软土中的应用

通过运用扁铲侧胀仪(DMT)在长江入海口滨海沉积软土中进行的原位测试,获得滨海沉积软土中扁铲侧胀试验各指标参数的变化规律。扁铲侧胀试验与静力触探试验结果一致,试验结果可靠,且扁铲侧胀试验可以快速地获取侧向基床反力系数KH,为桩基础的设计提供可靠的依据。对比旁压试验结果,扁铲侧胀试验得到的KH值常常偏大。在粘土层、粘质粉土夹粉质粘土、淤泥质粉质粘土、粘质粉土、淤泥质粘土等土层中KH与真实值相差较小,可以使用,但实际应用中应同时结合规范使用;而在砂质粉土和粉砂等土层中KH与真实值相差较大,不宜使用。     

Groundwater potentiometric decline in the Springfield, Missouri area

The decline of the potentiometric surface of the Ozark aquifer underneath Springfield Missouri intensified during the 1980s and has been of concern since. From 1990 to the present, the shifting of population from urban to rural areas and water management changes to use more surface water created an opportunity for groundwater levels to recover. However, in 2002 private well owners reported low levels and water problems, which prompted mapping the new cone of depression. To this purpose, well data measured from private wells and data available elsewhere were mapped using GIS mapping tools. The results show a cone of depression extending towards the recently developed areas south of Springfield while the potentiometric levels of some areas within the city had recovered. The maps show that, compared to the 1987 conditions, the present cone of depression has changed significantly in extent and shape while its maximum depth has changed only slightly.     

Discrete element modelling of deep penetration in granular soils

This paper presents a numerical study on deep penetration mechanisms in granular materials with the focus on the effect of soil–penetrometer interface friction. A two‐dimensional discrete element method has been used to carry out simulation of deep penetration tests on a granular ground that is under an amplified gravity with a K₀ lateral stress boundary. The numerical results show that the deep penetration makes the soil near the penetrometer move in a complex displacement path, undergo an evident loading and unloading process, and a rotation of principal stresses as large as 180°. In addition, the penetration leads to significant changes in displacement and velocity fields as well as the magnitude and direction of stresses. In general, during the whole penetration process, the granular ground undergoes several kinds of failure mechanisms in sequence, and the soil of large deformation may reach a stress state slightly over the strength envelope obtained from conventional compression tests. Soil–penetrometer interface friction has clear effects on the actual penetration mechanisms. Copyright © 2005 John Wiley & Sons, Ltd.