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Test method for simulating variation of permeability coefficient of foundation pit precipitation soil

A technology of permeability coefficient and test method, which is applied in the field of simulating the change of the permeability coefficient of the foundation pit dewatering soil in the soft soil layer, can solve the problems of not considering the influence of the permeability coefficient of the foundation pit dewatering soil and the unreasonable results.

Inactive Publication Date: 2010-12-15
TONGJI UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In the design, calculation and construction of deep foundation pits in soft soil strata, most of the current permeability coefficients are selected using the material parameters before precipitation, or only based on experience, without considering the influence of foundation pit precipitation on the soil permeability coefficient, and the results are obvious. Not reasonable enough

Method used

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  • Test method for simulating variation of permeability coefficient of foundation pit precipitation soil
  • Test method for simulating variation of permeability coefficient of foundation pit precipitation soil
  • Test method for simulating variation of permeability coefficient of foundation pit precipitation soil

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] Specific steps are as follows:

[0027] (1) Cut the undisturbed soil sample with a soil cutting ring knife with an inner diameter of 61.8mm and a height of 20mm, and paste filter paper at both ends of the sample;

[0028] (2) Connect the osmotic pressure container with the seepage flow pipeline and the seepage flow metering tube, let the water in the metering tube flow into the osmotic pressure container, so that the permeable stone in the entire pipeline and the osmotic pressure container is fully exhausted and saturated, and then close the valve;

[0029] (3) Put the ring knife with the soil sample up into the osmotic pressure container; put an O-shaped water stop ring on the outside of the ring knife, put a directional gasket, and screw on the compression screw; Install the permeable stone and the pressure transmission piston;

[0030] (4) The sample is consolidated in two stages through the pressure regulating valve. The first consolidation restores the sample to t...

Embodiment 2

[0035] The sample is the undisturbed soil taken from a deep foundation pit in the urban area of ​​Shanghai. The sample soil is gray muddy clay of layer ④, with a buried depth of 9.5-17.5m and a weight of 16.7kN / m 3 , the average self-weight stress is 100.0kPa. The test simulated four working conditions of no precipitation and 2.0m, 4.0m, and 8m of precipitation, and the corresponding consolidation pressures were 100.0kPa, 120.0kPa, 140.0kPa, and 180.0kPa; The samples were consolidated in two stages; a total of 4 groups of tests were done. Table 1 shows the vertical permeability coefficient of gray silty clay soil in layer ④ before and after precipitation measured according to the above test procedures. The variation curve of vertical permeability coefficient of layer ④ gray silty clay with precipitation depth is shown in image 3 shown.

Embodiment 3

[0037] The sample is the undisturbed soil taken from a deep foundation pit in the urban area of ​​Shanghai. The sample soil is ⑤-1 layer of gray clay, with a buried depth of 17.5-22.0m and a weight of 17.5kN / m 3 , the average self-weight stress is 150.0kPa. The test simulated four working conditions of no precipitation and 2.0m, 4.0m, and 8.0m of precipitation, and the corresponding consolidation pressures were 150.0kPa, 170.0kPa, 190.0kPa, and 230.0kPa; The precipitation samples were consolidated in two stages; a total of 4 groups of tests were done. Table 1 shows the vertical permeability coefficient of the gray clay layer ⑤-1 before and after precipitation measured according to the above test procedures. ⑤ The variation curve of the vertical permeability coefficient of the gray clay layer ⑤-1 with the precipitation depth is shown in Figure 4 shown.

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Abstract

The invention relates to a test method for simulating variation of a permeability coefficient of foundation pit precipitation soil, which comprises the following steps of: cutting an undisturbed sample by using a cutting ring and sticking filter paper at both ends of the sample; communicating an osmoticpressure container with a seepage pipeline and a seepage metering pipe to make porous stones in the whole pipeline and the osmoticpressure container subjected to sufficient exhaust saturation, and closing a valve; arranging the cutting ring with the undisturbed sample into the osmoticpressure container in a mode that the cutting edge is upward, sleeving a water stop ring and a directed gasket outside the cutting ring, compressing the water stop ring and the directed gasket and arranging the porous stones and a pressure transmitting piston at the upper end of the sample; carrying out two-stage consolidation on the sample through a pressure regulating valve, wherein the first consolidation makes the sample recovered into a natural geostatic stress state of soil mass and the second consolidation simulates the stress state of the soil mass after precipitation; and after completing consolidation, opening a seepage valve and starting a subsequent seepage test. Influences of the decrease of moisture content of the foundation pit precipitation soil, the increase of effective stress and the consolidation of soil on the permeability coefficient are considered, and the method provides a basis for accurate selection of the permeability coefficient of the foundation pit precipitation soil so as to provide guarantee for designing and constructing a soft watery deep foundation pit safely, economically and reasonably.

Description

technical field [0001] The invention relates to an indoor geotechnical test method, in particular to a test method for simulating the variation of the permeability coefficient of precipitation soil in foundation pits of soft soil layers. Background technique [0002] Soil permeability refers to the property of how easily water flows through the pores in the soil. The permeability coefficient is an important physical index to measure the permeability of the soil. It is used to analyze and calculate the foundation consolidation settlement, evaluate the seepage stability of foundation pits, earth dam embankments, and the design of foundation pit drainage and foundation reinforcement design. Required basic parameters. However, there are many factors affecting the permeability coefficient, including soil particle composition, compactness, saturation, temperature and structure, etc., which all have an important impact on the permeability coefficient. In engineering practice, the...

Claims

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Application Information

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IPC IPC(8): G01N15/08
Inventor 丁春林姚笑青叶丹朱恺
Owner TONGJI UNIV
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