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Determination of the in situ engineering properties of foundation materials has always been a challenge for geotechnical engineers and, thus, several methods have been developed so far. Dynamic Cone Penetration (DCP) test is one of the most versatile amongst them. In the present research, a light weight simple DCP device was developed and used for evaluation of the engineering properties of sandy soils in laboratory conditions. The device consisted of an 8-kg hammer that drops over a height of 575 mm, and drives a 60° cone tip with 20 mm base diameter into the ground. To control the validation of the results, laboratory direct shear and plate load tests were used as reference tests. The soil sample was a poorly graded sandy soil (SP) taken from alluvial deposits of the Tehran plain. All DCP tests and PLTs were undertaken on compacted soil in a mould with 700 mm diameter and 700 mm height. Based on the results of the experiments, the relationships between Dynamic Penetration Index (DPI), relative density (Dr), modulus of elasticity (E), shear modulus (G), modulus of subgrade reaction (KS), and the friction angle of the soil were obtained with a high coefficient of determination (> 90%). The repeatability of the test results was also evaluated by calculating the coefficient of variations (Cv), which was less than 30% for all tests. 相似文献
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Donald A. Davidson 《地球表面变化过程与地形》1983,8(2):171-175
This short communication describes difficulties of sample preparation associated with the determination of plastic and liquid limits using a drop-cone penetrometer. Problems of sample packing, soil moisture distribution and degree of remoulding are identified. These problems are particularly relevant in influencing liquid limit values whilst the effects on plastic limits are less marked. It is concluded that if the need is for the quick determination of liquid and plastic limits for general classification purposes, then the traditional Casagrande and thread methods are adequate. If these limits require to be measured with greater precision using the drop-cone technique, then careful consideration must be given to sample preparation. 相似文献
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The penetration of rigid objects such as piles and penetrometers into soils creates a zone of soil disturbance around them. The extent of this disturbed zone influences the resistance of the moving rigid body. This paper presents a theoretical framework to analyze the resistance in the disturbed zone created by a shaft penetrating a clay soil. The soil is modeled as a viscous material after it reaches failure [critical state (CS)]. The results of this analysis show that the viscous drag stress component on the shaft surface is influenced by the size of disturbed zone that has reached CS around the shaft, the shear viscosity of the soil and the velocity profile (or strain rate) in the CS zone around the shaft. The size of CS zone, the velocity profile and the viscosity of soil are interdependent. Large variation in viscous drag occurs when the size of the CS soil zone is less than four times the shaft’s radius. Limiting drag occurs when the size of the CS soil zone exceeds six times the shaft’s radius. The theoretical velocity distribution of the movement of soil in the CS zone shows that the soil is dragged along with shaft in the near field (close to the shaft surface) and moves upwards in the far field. 相似文献
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自落式贯入仪(Free-Falling Penetrometer, FFP)是一种新型海底沉积物原位测量设备,用于海底沉积物工程性质原位调查。本文基于自主研发的FFP设备在黄海海域开展现场贯入试验,分析探头尺寸对判断沉积物性质的影响。研究表明,在不同沉积物中探头尺寸对贯入深度、贯入阻力和沉积物类型判断有不同影响。在细粒沉积物中探头尺寸对贯入深度、贯入阻力影响较小;在根据贯入阻力变化划定分层时,小直径探头能反应贯入阻力更为细小的变化。在粗粒沉积物中探头尺寸影响更明显,大尺寸探头使贯入阻力变大,贯入深度减小。根据标准化深度和硬度因子可区分粗粒沉积物和细粒沉积物,在粗粒沉积物中探头尺寸增大,硬度因子减小,有利于细化沉积物类型。 相似文献
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This paper describes the construction of an inexpensive, lightweight, free-fall lake sediment penetrometer with application to paleolimnological research. This penetrometer is suitable for use in a variety of fresh water lake settings. Data are collected on a laptop PC, Palm OS handheld, or a Texas Instruments handheld data collection unit and are analysed using commercially available software. The quality of these data are adequate for determining changes in substrate type based on hardness. The unit can also be used to locate sites for optimum penetration of gravity cores and to calibrate sonar records. Addition of up to three optional transducers could expand the capabilities of the unit. Other potential uses include the determination of specific geotechnical properties of the lake sediment including the undrained shear strength. 相似文献
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Particle crushing occurs near the tip of a penetrometer and influences the development of the tip resistance.To study particle crushing near a penetrometer tip,a cone penetrometer was monotonically jacked and then load-tested in medium dense and dense silica sand samples prepared in a halfcylindrical calibration chamber with viewing windows.During the tests,images of the advancing penetrometer and the surrounding soil were taken using digital cameras and analyzed to obtain the displacement and strain fields around the penetrometer using the Digital Image Correlation(DIC)technique.Subsequently,soil samples were collected near the tip of the penetrometer using a novel agarimpregnation technique and digitized using an X-ray microscope.The digitized samples were analyzed to reconstruct the three-dimensional models of individual particles,generating the gradation and relative breakage parameters of the sand around the cone penetrometer. 相似文献
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