Measuring device and method of apparent viscosity of saturated sand in high pore pressure ratio state

Abstract

The invention relates to measuring device and method of the apparent viscosity of saturated sand in a high pore pressure ratio state. The measuring device comprises a model box and an external water box, wherein the external water box can regulate the height of a water surface; a flexible pipe is led from the bottom of the water box and penetrates through an opening positioned at the bottom of the model box to connect with a water outlet pipe inside the model box; a hard board with the opening is placed on the lower part inside the model box; a rigid sphere with both ends hauled by haulage ropes is placed on a horizontal track inside the model box; and the haulage ropes are led out of the model box through a fixed pulley block and connected with a forward and reverse rotating speed-regulating motor. The measuring method comprises the following steps of: enabling the saturated sand inside the model box to be in a super-pore pressure ratio state before liquification by changing a water level of the external water box; enabling the speed-regulating motor to drive the rigid sphere to take horizontal movement on the track, and measuring the speed and the resistance of the rigid sphere; and calculating the apparent viscosity of the saturated sand before the liquification. The invention solves the problem of measurement of the apparent viscosity of the saturated sand in the high pore pressure ratio state before the liquification and has the advantages of easy test operation, high efficiency and low border effect.

Description

technical field [0001] The invention relates to a viscosity measuring device and method, in particular to a device and method for measuring the apparent viscosity of saturated sandy soil with high pore pressure ratio. Background technique [0002] Liquefaction characteristics of sandy soil is a research hotspot in soil dynamics. The total stress of saturated sand is composed of effective stress and pore water pressure. Generally, due to the existence of effective stress, the pore water pressure of sand is less than the total stress. However, under dynamic loads such as earthquakes and explosions, the pore water pressure in the saturated sand will continue to rise. When the pore water pressure increases to equal the total stress, the effective stress in the sand is equal to zero, and the sand skeleton is lost. When the force is exerted, the sand particles are "suspended" in the water. At this time, the sand becomes a fluid-like substance and loses its shear strength and bear...

AI Technical Summary

Problems solved by technology

However, none of the above-mentioned viscosity measurement methods can effectively measure the apparent viscosity of saturated sand in the state of high pore pressure ratio before liquefaction, for the following reasons:

[0005] (1) When the falling ball viscometer measures, the rigid ball falls by gravity, and the apparent viscosity of the fluid is calculated by measuring the speed of the rigid ball passing through the fluid at a constant speed, while the saturated sand is in a state of high pore pressure ratio. There is still a certain interaction force between them, and the gravity of the rigid ball alone cannot pass through the fluid at a uniform speed. Therefore, the traditional falling ball viscometer is not suitable for the measurement of the apparent viscosity of the saturated sandy soil under the state of high pore pressure.

[0006] (2) The capillary viscometer needs to use a slender glass tube, the rotational viscometer requires the fluid to flow in shear in the slit, and the sand has a certain particle size The material cannot flow smoothly in the slender glass tube or slit, so the apparent viscosity of liquefied sand is not suitable for measurement by capillary viscometer and rotational viscometer

[0008](4) It has been proved by experiments that the apparent viscosity of saturated sandy soil before liquefaction is very high, beyond the measurement range of conventional viscometers

[0009](5) The rate of flow deformation of saturated sandy soil is low when the pore pressure ratio is high, while the rate of fluid movement is relatively high when measured by a conventional viscometer. It cannot reasonably reflect the characteristics of flow deformation in the state of high pore pressure ratio before saturated sand liquefaction

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