CN109653260B - Settlement calculation method of coral sand foundation based on secondary compression coefficient of vibration environment - Google Patents

Abstract

The invention relates to a settlement calculation method of a coral sand foundation based on a secondary compression coefficient of a vibration environment. The method fills the blank of the testing method of the secondary compression coefficient under the action of coral sand vibration load, uses the secondary compression coefficient to calculate the settlement deformation of the coral sand foundation, and has profound significance for the subsequent hydraulic reclamation construction, engineering design and construction of coral island reefs.

Description

Settlement calculation method of coral sand foundation based on secondary compression coefficient of vibration environment

Technical Field

The invention discloses a settlement calculation method of a coral sand foundation based on a secondary compression coefficient in a vibration environment, and belongs to the technical field of testing.

Background

Coral sand is a special rock-soil medium rich in calcium carbonate or other insoluble carbonate substances, which is usually caused by marine organisms (coral, seaweed, shell, etc.), and is also called calcareous soil. The main mineral component of the method is calcium carbonate (> 50%), which is a carbonate deposit which is greatly different from a terrestrial deposit and is formed in a saturated calcium carbonate solution for a long time through physical, biochemical and chemical action processes (including organic debris crushing and cementing processes and certain pressure, temperature and solubility change processes). As the deposition process is mostly not carried for a long distance, the reasons of fine pores in the original biological skeleton and the like are kept, the formed soil particles are porous (containing internal pores), irregular in shape, easy to break, easy to bond and the like, so that the engineering mechanical properties of the soil particles are obviously different from those of common continental facies and marine facies sediments, and the soil particles have obvious secondary compression characteristics. Island reef filled by coral sand is generally located in the ocean and is influenced by tides and the like, and the vibration environment has a larger difference compared with the continent, so that the study of secondary compression characteristics of the coral sand foundation in the island reef vibration environment is particularly important for calculating the settlement deformation of the coral sand foundation. The settlement deformation of the coral sand foundation in a vibration environment is deeply researched, and the method has great significance for the engineering design and construction of coral island reefs, national defense construction enhancement and the like.

Disclosure of Invention

The invention provides a settlement calculation method of a coral sand foundation based on a secondary compression coefficient of a vibration environment, which is designed and provided aiming at the prior art, and aims to simulate the vibration environment of coral sand reclamation islands through an indoor artificial vibration source, measure the secondary compression coefficient of the coral sand foundation by a compression test device, and then calculate the settlement deformation of the coral sand foundation by using the secondary compression coefficient, wherein the meaning of the secondary compression coefficient is shown in figure 1.

The purpose of the invention is realized by the following technical scheme:

the settlement calculation method of the coral sand foundation based on the secondary compression coefficient of the vibration environment is characterized by comprising the following steps of: the method comprises the following steps:

firstly, in an indoor laboratory for placing a compression instrument for geotechnical tests, a coral sand sample is manufactured according to the standard of geotechnical test methods (GB/T50123-1999), the coral sand sample is placed in the compression instrument, a set of vibration source capable of adjusting frequency and amplitude is arranged in the laboratory to provide a vibration environment for the compression instrument, the frequency range of the vibration source is adjustable to be 1-50 Hz, and the amplitude range of the vibration source is adjustable to be 10^-7～10^-3m/s²Adjusting the frequency and amplitude of the vibration environment to be consistent with the ground pulsation environment of the coral sand island reef to be engineered, setting the pressure of a compressor according to the pressure required by the engineering, performing a compression test on the coral sand sample, and drawing a deformation-time logarithmic curve under the vibration environment according to test data;

dividing the curve into an initial compression stage A-B, a main compression stage B-C, a secondary compression stage IC-D and a secondary compression stage II D-E according to the time sequence on a deformation-time logarithmic curve in a vibration environment, wherein a point A is a test starting point, a point E is a test end point, the initial compression stage A-B and the compression stage II D-E are straight line segments, the main compression stage B-C and the secondary compression stage IC-D are curve segments, and a point D is an intersection point of a straight line fitted in the compression stage I and a straight line in the secondary compression stage II D-E;

step three, calculating the secondary pressure of the secondary compression stage IC-DSub-compression coefficient C of the compression stage_αvⅠAnd a secondary compression coefficient C of a secondary compression stage of the secondary compression stages IID-E_αvⅡThe calculation formula is as follows:

C_αvⅠ＝(d_Ⅰ2-d_Ⅰ1)/(d₀·lg(t_Ⅰ2/t_Ⅰ1))

in the formula:

d_Ⅰ1on the C-D test section, experience t_Ⅰ1Height variation (mm) of sample at test time (min)

d_Ⅰ2On the C-D test section, experience t_Ⅰ2Height variation (mm) of sample at test time (min)

d₀Initial height of the sample (mm)

C_αvⅡ＝(d_Ⅱ2-d_Ⅱ1)/(d₀·lg(t_Ⅱ2/t_Ⅱ1))

In the formula:

d_Ⅱ1on D-E test section, experience t_Ⅱ1Height variation (mm) of sample at test time (min)

d_Ⅱ2On D-E test section, experience t_Ⅱ2Height variation (mm) of sample at test time (min)

d₀-initial height of the specimen (mm);

step four, according to the secondary compression coefficient C_αvⅠ、C_αvⅡCalculating settlement deformation of coral sand foundation

S_creepv＝C_αvⅠ·H₀·(lgt_d-lgt_start)+C_αvⅡ·H₀·(lgt_end-lgt_d)

In the formula:

H₀thickness of foundation soil layer of coral sand

t_start-time of start of compression (min)

t_dTime (min) for transition from the first compression stage to the second compression stage

t_end-calculating the cut-off time (min) for the sub-compression.

The method simulates the vibration environment of coral sand reclamation island reef through an indoor artificial vibration source, measures the secondary compression coefficient of the coral sand foundation through a compression test device, and calculates the settlement deformation of the coral sand foundation by using the secondary compression coefficient.

Drawings

FIG. 1 is a diagram showing the meaning of the secondary compression factor in Craig's Soil mechanisms (Eighth Edition)

FIG. 2 is a logarithmic deformation-time curve under a vibration environment plotted in an embodiment of the present invention

Detailed Description

The invention will be further described in detail with reference to the following figures and examples:

in this embodiment, a concrete runway is constructed on coral sand foundation in a certain sea area, and the thickness H of coral sand stratum from the part below the runway to between reef and limestone₀The settlement calculation method of the coral sand foundation based on the secondary compression coefficient of the vibration environment comprises the following steps:

step one, adjusting an artificial vibration source to enable the vibration environment in a laboratory to be consistent with a construction site

In a laboratory for placing a compression instrument for geotechnical test, coral sand samples are prepared according to the standard of geotechnical test method (GB/T50123-1999), and placed in the compression instrument, and the samples are taken from the coral sand samples in the field, wherein the dry density of the coral sand samples is 1.43g/cm³The particle density was 2.78g/cm³Height d of sample₀Is 20 mm;

a set of vibration source capable of adjusting frequency and amplitude is arranged in a laboratory to provide a vibration environment for the compressor, the frequency range of the vibration source is 1-50 Hz, and the amplitude range is 10^-7～10^-3m/s²Adjusting the frequency and amplitude of the vibration environment to be consistent with the ground pulsation environment of the coral sand island reef to be engineered, setting the pressure of a compressor according to the pressure required by the engineering, performing a compression test on the coral sand sample, and drawing a deformation-time logarithmic curve under the vibration environment according to test data;

dividing the curve into an initial compression stage A-B, a main compression stage B-C, a secondary compression stage IC-D and a secondary compression stage II D-E according to the time sequence on a deformation-time logarithmic curve in a vibration environment, wherein a point A is a test starting point, corresponds to the beginning of the runway repair time of 200 days, a point E is a test ending point, corresponds to the end of the runway design life of 30 years, corresponds to the initial compression stage A-B and the compression stage II D-E of 5 years of the first runway repair evaluation time, is a straight line segment, is a curve segment, and is a point D which is the intersection point of a straight line fitted in the compression stage I and a straight line in the secondary compression stage II D-E;

the sub-compression stages IC-D are subjected to t_Ⅰ1The height change value d of the sample is 12min_Ⅰ1Is 0.101mm, and experiences t_Ⅰ2The height change value d of the sample is 4320min_Ⅰ20.1319 mm; the secondary compression stage IID-E experiences t_Ⅱ1When the test time is 12960min, the height change value d of the sample_Ⅱ10.1401mm, over a period of t_Ⅱ2The height change value d of the sample is 77760min_Ⅱ2(0.1895mm)；

Step three, calculating a secondary compression coefficient C of a secondary compression stage of the secondary compression stages IC-D_αvⅠAnd a secondary compression coefficient C of a secondary compression stage of the secondary compression stages IID-E_αvⅡThe calculation formula is as follows:

C_αvⅠ＝(d_Ⅰ2-d_Ⅰ1)/(d₀·lg(t_Ⅰ2/t_Ⅰ1))

＝(0.1319-0.101)/(20*lg(4320/12))

＝0.0006

in the formula:

d_Ⅰ1on the C-D test section, experience t_Ⅰ1Height variation (mm) of sample at test time (min)

d_Ⅰ2On the C-D test section, experience t_Ⅰ2Height variation (mm) of sample at test time (min)

d₀Initial height of the sample (mm)

C_αvⅡ＝(d_Ⅱ2-d_Ⅱ1)/(d₀·lg(t_Ⅱ2/t_Ⅱ1))

＝(0.1895-0.1401)/(20*lg(77760/12960)

＝0.0032

In the formula:

d_Ⅱ1on D-E test section, experience t_Ⅱ1Height variation (mm) of sample at test time (min)

d_Ⅱ2On D-E test section, experience t_Ⅱ2Height variation (mm) of sample at test time (min)

d₀-initial height of the specimen (mm);

step four, according to the secondary compression coefficient C_αvⅠ、C_αvⅡCalculating settlement deformation of coral sand foundation

S_creepv＝C_αvⅠ·H₀·(lgt_d-lgt_start)+C_αvⅡ·H₀·(lgt_end-lgt_d)

＝0.0006*8000*(lg(5*365*1440)-lg(200*1440))+0.0032*8000*(lg(30*365*1440)-lg(5*365*1440))

＝0.0006*8000*0.9602+0.0032*8000*0.7782

＝24.5mm

In the formula:

H₀thickness of foundation soil layer of coral sand

t_start-time of start of compression (min)

t_dTime (min) for transition from the first compression stage to the second compression stage

t_end-calculating the cut-off time (min) for the sub-compression.

The coral sand compression test in the vibration environment shows secondary compression characteristics at 10000-.

And the effect of guiding construction is achieved according to the calculation data, the airport runway enters a test flight stage after being built for 1 year, and the settlement observation data is displayed to be basically consistent with the settlement calculation result.

Claims (1)

1. A settlement calculation method of a coral sand foundation based on a secondary compression coefficient of a vibration environment is characterized by comprising the following steps: the method comprises the following steps:

firstly, in an indoor laboratory for placing a compression instrument for geotechnical tests, a coral sand sample is manufactured according to the standard of geotechnical test methods (GB/T50123-1999), the coral sand sample is placed in the compression instrument, a set of vibration source capable of adjusting frequency and amplitude is arranged in the laboratory to provide a vibration environment for the compression instrument, the frequency range of the vibration source is adjustable to be 1-50 Hz, and the amplitude range of the vibration source is adjustable to be 10^-7～10^-3m/s²Adjusting the frequency and amplitude of the vibration environment to be consistent with the ground pulsation environment of the coral sand island reef to be engineered, setting the pressure of a compressor according to the pressure required by the engineering, performing a compression test on the coral sand sample, and drawing a deformation-time logarithmic curve under the vibration environment according to test data;

dividing the curve into an initial compression stage A-B, a main compression stage B-C, a secondary compression stage IC-D and a secondary compression stage II D-E according to the time sequence on a deformation-time logarithmic curve in a vibration environment, wherein a point A is a test starting point, a point E is a test end point, the initial compression stage A-B and the secondary compression stage II D-E are straight line segments, the main compression stage B-C and the secondary compression stage IC-D are curve segments, and a point D is an intersection point of a straight line fitted in the compression stage I and a straight line in the secondary compression stage II D-E;

step three, calculating a secondary compression coefficient C of a secondary compression stage of the secondary compression stages IC-D_αvⅠAnd a secondary compression coefficient C of a secondary compression stage of the secondary compression stages IID-E_αvⅡThe calculation formula is as follows:

C_αvⅠ＝(d_Ⅰ2-d_Ⅰ1)/(d₀·lg(t_Ⅰ2/t_Ⅰ1))

in the formula:

d_Ⅰ1on the C-D test section, experience t_Ⅰ1Height variation (mm) of sample at test time (min)

d_Ⅰ2On the C-D test section, experience t_Ⅰ2Height variation (mm) of sample at test time (min)

d₀Initial height of the sample (mm)

C_αvⅡ＝(d_Ⅱ2-d_Ⅱ1)/(d₀·lg(t_Ⅱ2/t_Ⅱ1))

In the formula:

d_Ⅱ1on D-E test section, experience t_Ⅱ1Height variation (mm) of sample at test time (min)

d_Ⅱ2On D-E test section, experience t_Ⅱ2Height variation (mm) of sample at test time (min)

d₀-initial height of the specimen (mm);

step four, according to the secondary compression coefficient C_αvⅠ、C_αvⅡCalculating settlement deformation of coral sand foundation

S_creepv＝C_αvⅠ·H₀·(lgt_d-lgt_start)+C_αvⅡ·H₀·(lgt_end-lgt_d)

In the formula:

H₀thickness of foundation soil layer of coral sand

t_start-time of start of compression (min)

t_dTime (min) for transition from the first compression stage to the second compression stage

t_end-calculating the cut-off time (min) for the sub-compression.

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