CN114018700A - Large-scale soil-rock mixed soil sample indoor compression instrument and filling deformation and stability calculation method - Google Patents

Large-scale soil-rock mixed soil sample indoor compression instrument and filling deformation and stability calculation method Download PDF

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CN114018700A
CN114018700A CN202111246175.7A CN202111246175A CN114018700A CN 114018700 A CN114018700 A CN 114018700A CN 202111246175 A CN202111246175 A CN 202111246175A CN 114018700 A CN114018700 A CN 114018700A
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sample
soil
pressure
formula
phi
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苏美亮
贾宁
刘顺
王洪播
张�杰
蔡雨辰
张国龙
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North China Power Engineering Co Ltd of China Power Engineering Consulting Group
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/32—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring the deformation in a solid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/067—Parameter measured for estimating the property
    • G01N2203/0676—Force, weight, load, energy, speed or acceleration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/067—Parameter measured for estimating the property
    • G01N2203/0682—Spatial dimension, e.g. length, area, angle

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Abstract

The invention provides a large soil-rock mixed soil sample indoor compression instrument and a method for calculating the deformation and stability of filled soil, wherein the compression instrument comprises a loading and testing system and a sample accommodating device, the sample accommodating device comprises a retaining ring for accommodating a sample, a quantitative humidifier connected with the sample and a plurality of pressure boxes arranged along the circumferential direction of the sample; the loading and testing system comprises a jack pressurized at the top of the sample, an automatic control and recording device in control connection with the jack, and a pressure sensor in two-way connection with the automatic control and recording device, and a plurality of displacement sensors are arranged at the top of the sample.

Description

Large-scale soil-rock mixed soil sample indoor compression instrument and filling deformation and stability calculation method
Technical Field
The invention relates to the field of indoor soil body compression, in particular to a large soil-rock mixed soil sample indoor compression instrument and a method for calculating the deformation and stability of filling soil.
Background
In recent years, with the increasing shortage of engineering land in China and the consideration of the influence on human living environment during engineering construction and operation, large-scale engineering projects such as power plants, transformer substations and the like are located in mountainous areas. The geological conditions of mountainous areas are complex, and in order to ensure the excavation and filling balance as much as possible in the field flat backfilling process, most of the filling adopted in the filling area is a mixture of residual slope accumulated soil in the excavation area and broken materials of strongly weathered and moderately weathered rocks. The difference of the particle sizes of the mixture is large, and the test requirement of the soil-rock mixture can not be met due to the small diameter of a sample of a compression tester used in a traditional geotechnical test room. Engineering property parameters of the earth-rock mixture are difficult to obtain, so that foundation deformation in a filling area, foundation pit support in the filling area and slope stability evaluation become a difficult problem in the geotechnical engineering industry.
The settlement of the earth surface of the filling area is generally larger, and the specific value is related to the property of the filling material, the filling process and the compactness degree of the final filling material. In fact, a concern in engineering practice is the completion of the fill in the fill area, the settlement from the fill after the settlement-sensitive building or equipment is in place, which is also called post-construction settlement. According to engineering experience, the post-construction settlement is usually 0.1-3% of the thickness of the filling. Excessive post-construction settlement is a main reason for inclination and cracking of engineering (structure) buildings and incapability of normal operation of equipment.
Under the influence of atmospheric precipitation and pipeline leakage, after pores in a soil body are filled with water, the strength of the soil body can be weakened due to overhigh water content, the soil body in a fill area is often subjected to additional compression after being soaked or humidified, and ground settlement caused by the partial compression is also an important factor causing engineering accidents, so that the performance of saturated soil needs to be measured in advance.
The traditional compression test has the test indexes of deformation parameters such as compression modulus, compression index, rebound index, secondary consolidation coefficient and the like, and can not simulate the soil engineering properties after humidification; the parameters of the lateral pressure coefficient and the internal friction angle required by the foundation pit support design and the side slope design can not be obtained.
Disclosure of Invention
The invention increases the size of the traditional compression instrument to meet the test requirement of the large-particle-size soil-rock mixture, and the obtained parameters can be used for calculating and evaluating the settlement after the soil filling work; the quantitative humidifying function of the soil sample is added, so that the additional settlement generated after the soil filling is humidified or soaked can be simulated; meanwhile, the function of testing the lateral limit annular pressure of the sample is also added, the lateral pressure coefficient of the mixture can be obtained, and the excitation angle and the internal friction angle are further obtained through theoretical analysis, so that parameters can be provided for foundation pit support and side slope design in a soil filling area.
The technical means adopted by the invention are as follows,
a large soil-rock mixed soil sample indoor compression instrument comprises a loading and testing system and a sample accommodating device, wherein the sample accommodating device comprises a retaining ring for accommodating a sample, a quantitative humidifier connected with the sample and a plurality of pressure boxes arranged along the circumferential direction of the sample; the loading and testing system comprises a jack pressurized at the top of the sample, an automatic control and recording device in control connection with the jack, a pressure sensor in two-way connection with the automatic control and recording device, and a plurality of displacement sensors arranged at the top of the sample.
Preferably, the lower part of the retaining ring is further provided with a base, the base and the retaining ring enclose an accommodating space with an open top, and in the accommodating space: the inner wall of the supporting ring is provided with a cutting ring, the sample is arranged in the cutting ring, the pressure box is arranged between the sample and the cutting ring, the upper and lower parts of the sample are respectively provided with an upper permeable steel plate and a lower permeable steel plate, and a pressurizing cover plate is arranged above the upper permeable steel plate.
Preferably, a water inlet pipe and a humidifying pipe are respectively connected and arranged below the lower permeable steel plate, and a quantitative humidifier is arranged on the humidifying pipe; the upper part of the upper permeable steel plate is respectively connected with a drain pipe and an exhaust pipe, and the exhaust pipe is communicated with a humidifying pipe.
Preferably, the jack is carried by a two-column loading frame, and the jack is pressed on the pressure cover plate.
The method for calculating the filling deformation and stability of the indoor compression instrument based on the large soil-rock mixed soil sample applies pressure to the sample through an automatic control and recording device, and calculates the deposition amount of the conventional soil sample generated by secondary consolidation after the main consolidation is finished through the following formula:
Figure BDA0003321053790000021
Figure BDA0003321053790000022
in the formula, Ss-creep compression of the fill itself;
hi-thickness of the ith soil layer;
e0i-the porosity ratio at the beginning of the i-th layer post-earthworking settlement timing;
e1i-the porosity ratio at the end of the main consolidation settlement of the ith layer of soil under overburden loading;
t1-is the time at which the primary consolidation settlement of the ith layer of soil under the action of the overburden load is finished;
t1' - - -is the time at which the post-construction settlement timer begins;
Cai-secondary consolidation coefficient of the i-th layer of soil under the action of overburden;
t-the time of settlement after construction is equal to the engineering design age, and 50 years are taken;
lambda-correction factor, taken as 1 without experience.
Preferably, the pore ratio e after the consolidation of the sample is stabilized at each stage of pressureiCan be obtained by the following formulaDetermining the porosity ratio e of the ith layer of soil at the end of main consolidation settlement under the action of the overburden load1i：
Figure BDA0003321053790000031
And
Figure BDA0003321053790000032
in the formula, ei-the void ratio of the sample after consolidation and stabilization at each stage of pressure; e.g. of the type0-initial porosity ratio, dimensionless; w is a0-initial moisture content of the sample, dimensionless; gs-specific gravity, dimensionless, of rock or soil particles in the sample; rhowDensity of water, g/cm3；ρ0Density of the sample, g/cm3；h0-initial height of the specimen (mm); Δ hi-the deformation (mm) of the sample after consolidation stabilization at a certain level of pressure;
wherein C isaThe slope of the void ratio versus time (log) curve at each stage of pressure can be determined by the following equation:
Figure BDA0003321053790000033
and the unit sedimentation amount S after the sample is stably solidified at each stage of pressurei(mm/m) is calculated by the formula
Figure BDA0003321053790000034
Preferably, the compression coefficient a within a certain pressure range can be further determined from the pore ratio of the sample after the consolidation is stabilized at each pressure stagev(MPa-1) Is calculated by the formula
Figure BDA0003321053790000035
In the formula piTo a certain pressure value (MPa)，
Further, a compression modulus E in a certain order of pressure ranges(MPa) is as follows
Figure BDA0003321053790000041
And, a compressibility index C over a range of pressurescAnd rebound index CsIs calculated by the formula
CcOr
Figure BDA0003321053790000042
Preferably, the automatic control and recording device applies pressure to the sample, after the compression deformation of the sample is stable, the quantitative humidifier or the water inlet pipe humidifies or soaks the sample, the value of the displacement sensor is read, and the additional deposition amount generated after the sample is humidified or soaked by water is calculated through the following formula:
Figure BDA0003321053790000043
in the formula,. DELTA.s-additional settlement (mm) of the fill sample; deltasi-additional compressibility of the i-th layer of soil; h isi-thickness of the i-th layer of soil (mm); alpha-correction coefficient considering the stress state of foundation soil under the substrate, the region and other factors;
wherein at a certain pressure the additional compressibility factor delta of the samplesCalculated by the following formula:
Figure BDA0003321053790000044
in the formula, deltas-additional compressibility of the sample at a certain level of pressure; h isp-height (mm) after deformation stabilization before sample humidification; h isp' - - -height (mm) after stabilization of deformation after humidification of the sample, i.e., at a certain water content; h is0-initial height of the sample (mm).
Preferably, when the automatic control and loading device applies pressure to the sample, the vertical pressure σ is measured by the pressure sensor and the pressure cell, respectivelyvAnd horizontal pressure σhThe side limit envelope curve is prepared by the Morer circles under different stress states, and the excitation angle is phimobThe internal friction angle corresponding to the soil body strength envelope line is phi;
coefficient of static soil pressure K0Is Δ σhAnd Δ σvIs given by the formula
Figure BDA0003321053790000045
The known formula of the coefficient of the static soil pressure is
K0＝1-sinφ，
The right sides of the formulas of the two static soil pressure coefficients are equal to obtain phi and phimobThe relationship between them is:
Figure BDA0003321053790000051
preferably, phi and phimobWhen the relation between the two is more than or equal to 30 degrees and less than or equal to 45 degrees, the obtained product can be obtained
φ＝φmob+11.5°，
When phi is more than or equal to 20 degrees and less than or equal to 45 degrees, the relation can be simplified into
φ＝1.18φmob+6.66°；
And, the internal friction angle phi and the excitation angle phimobCan also be expressed as:
Figure BDA0003321053790000052
or phi is 1.56 phimob。
Compared with the prior art, the invention has the following advantages:
according to the invention, through the automatic control and recording device, continuous load is simulated, so that the compression deformation of the filling under the self action can be obtained, and further, the settlement after the conventional soil sample filling area is obtained; and the quantitative humidifier, the water inlet device, the water discharge device, the permeable steel plate and other devices are additionally arranged to increase the quantitative humidifying function of the sample, so that the settlement of accessories generated after the filling is humidified or soaked can be simulated; the invention is additionally provided with the pressure box to increase the test function of the lateral limit annular pressure of the sample, can obtain the lateral pressure coefficient (static soil pressure coefficient) of the mixture, further obtains the excitation angle and the internal friction angle through theoretical analysis, and can provide parameters for foundation pit support and side slope design of the soil filling area.
Drawings
FIG. 1 is a schematic diagram of a sample containment device according to the present invention;
FIG. 2 is a schematic diagram of a loading and testing system according to the present invention;
FIG. 3 is a plot of void ratio versus time (log);
FIG. 4 is a schematic view of post-construction consolidation compression calculations;
figure 5 is a schematic diagram of the soil intensity envelope and the side limit envelope.
The system comprises a loading and testing system 1, a sample containing device 2, an automatic control and recording device 3, a repeater 4, a load control box 5, an oil pump 6, a one-way valve 7, a pressure sensor 8, a pressure gauge 9, a two-column loading frame 10, a jack 11, a displacement sensor 12, a sample 13, a quantitative humidifier 14, a humidifying valve 15, a humidifying air pump 16, an air pump valve 17, a humidifying pipe 18, a water inlet pipe 19, a water inlet valve 20, a base 21, a permeable steel plate 22 below, a permeable steel plate 23 above, a pressure box 24, a cutting ring 25, a retaining ring 26, a pressurizing cover plate 27, a drainage pipe 28, a drainage valve 29, an exhaust pipe 30, an exhaust valve 31 and a sample 32, wherein the sample is loaded on the loading and testing system;
a main consolidation process, b consolidation processes, c secondary consolidation compression process completed before settlement timing after work, d secondary consolidation compression process after work, e strength envelope curve and f side limit envelope curve.
Detailed Description
Referring to fig. 1-5, the following examples are provided:
as shown in fig. 1-2, a large soil-rock mixed soil sample indoor compression instrument comprises a loading and testing system 1 and a sample containing device 2, wherein the sample containing device 2 comprises a retaining ring 26 for containing a sample 32, a quantitative humidifier 14 connected with the sample 32, and a plurality of pressure boxes 24 arranged along the circumferential direction of the sample 32; as shown in fig. 2, the loading and testing system 1 includes a jack 11 pressurized on the top of the test specimen 32, an automatic control and recording device 3 in control connection with the jack 11, a pressure sensor 8 in bidirectional connection with the automatic control and recording device 3, and a plurality of displacement sensors 12 arranged on the top of the test specimen 32. The jack 11 is controlled by the automatic control and recording device 3 through the load control box 5, the oil pump 6 and the one-way valve 7, and the relay 4 is arranged between the pressure sensor 8 and the automatic control and recording device 3 to realize the two-way connection of the two. Thus, when the jack 11 is controlled by the automatic control and recording device 3 to press the sample 32, the pressure sensor 8 can read the pressure value through the pressure gauge 9 and can transmit the pressure value back to the automatic control and recording device 3, if the pressure drops, automatic compensation is carried out, and the dead load under all levels of pressure is realized. Moreover, the automatic control and recording device 3 can also measure and store the measured value of the displacement sensor 12 at regular time. The displacement sensor 12 is generally provided with 4, and can be provided with 12 at most, and the average value is calculated to reduce the error.
As shown in fig. 1, a base 21 is further disposed at a lower portion of the guard ring 26, the base 21 and the guard ring 26 enclose an accommodating space with an open top, and in the accommodating space: a cutting ring 25 is arranged on the inner wall of the supporting ring 26, the sample 32 is arranged in the cutting ring 25, the pressure box 24 is arranged between the sample 32 and the cutting ring 25, the upper and the lower parts of the sample 32 are respectively provided with an upper permeable steel plate 22 and a lower permeable steel plate 23, and a pressurizing cover plate 27 is arranged above the upper permeable steel plate 22; a water inlet pipe 19 and a humidifying pipe 18 are respectively connected and arranged below the lower permeable steel plate 23, and a quantitative humidifier 14 is arranged on the humidifying pipe 18; a drain pipe 28 and an exhaust pipe 30 are respectively connected and arranged above the upper permeable steel plate 23, and the exhaust pipe 30 is communicated with the humidifying pipe 18. The humidifying air pump 16 is arranged on the humidifying pipe 18 where the quantitative humidifier 14 is arranged, and the humidifying valve 15, the air pump valve 17, the water inlet valve 20, the water outlet valve 29 and the air outlet valve 31 are correspondingly arranged on the quantitative humidifier 14, the humidifying air pump 16, the water inlet pipe 19, the water outlet pipe 28 and the air outlet pipe 30 respectively so as to be convenient to control.
As shown in fig. 2, the jack 11 is carried by the spar 10 and the jack 11 presses on the pressure cover plate 27.
The sample pressure test is carried out by a compression instrument as shown in figures 1-2, the concrete test process is that remolded soil is prepared in a large-scale cutting ring 25 according to the dry density and the water content required by the test, permeable steel plates are placed on the upper part and the lower part of the sample, after the automatic control and recording device 3 is provided with loading pressure control of all levels, the vertical pressure is applied to the sample 32 by a jack 11 above the sample, the load of each level is maintained at a constant load, and the lateral stress sigma of a pressure box 24 arranged in the cutting ring is read at a given time pointhAnd the displacement sensor 12 is used for measuring the displacement until the compression deformation of the soil sample is stable. The method comprises the following specific steps:
(1) the cutting ring 25 with the sample 32 is arranged in the protective ring 26, thin filter paper, a permeable steel plate and a pressurizing cover plate 27 are sequentially arranged on the sample 32, the sample is placed in the middle of a pressurizing frame, the pressurizing cover plate 27 is aligned with the center of the frame, and the displacement sensor 12 is installed;
(2) applying a pre-pressure of 1kPa to enable the sample to be in contact with the upper and lower parts of the instrument, and adjusting the pressure sensor 8 to measure and read an initial reading;
(3) the pressure levels required to be applied are determined and are preferably 12.5, 25, 50, 100, 200, 400, 800, 1600, 2500 kPa. The first stage pressure is determined according to the hardness of the soil sample, and is preferably 12.5kPa, 25kPa or 50kPa, wherein 12.5kPa is used for soft plastic, 25kPa is used for plastic, and 50kPa is used for hard plastic. The pressure of the last stage is greater than the sum of the self-weight pressure of the soil and the additional pressure;
(4) for samples that need to be saturated, the water inlet should be opened to submerge the sample immediately after the first stage of pressure is applied. When the unsaturated sample is subjected to a compression test, wet cotton yarns with the humidity equivalent to that of the sample are used for surrounding the periphery of the pressurizing plate;
(5) when the time-dependent sedimentation curve is to be measured, it is preferred to measure the height change of the sample in the following time sequence after each stage of pressure is applied. The time is 6s, 15s, lmin, 2min15s, 4min, 6min15s, 9min, 12min15s, 16min, 20min15s, 25min, 30min15s, 36min, 42min15s, 49min, 64min, 100min, 200min, 400min, 23h, 24h, and the time is up to the stable or planned end time(ii) a When the sedimentation rate is not required to be measured, measuring the height change of the sample 24 hours after each stage of pressure is applied to serve as a stable standard; only the sample of the compression coefficient is needed to be measured, after each stage of pressure is applied, the deformation per hour reaches 0.01mm as a stable standard, and the side pressure value sigma measured by the pressure box is read and recorded at the same timeh. Pressurizing step by step according to the steps until the test is finished;
(7) when a rebound test is required, the sample can be compressed and stably retreated under a certain level of pressure until the required pressure is retreated, and the rebound amount of the sample is measured after each time of retreating to 24 hours;
(8) after the experiment, demolish each part of instrument rapidly, take out monoblock sample, survey the moisture content, when the broken condition of granule is known to needs, can carry out particle analysis to whole samples.
According to the test process, parameters such as porosity ratio, sedimentation amount, compression coefficient, compression modulus, compression index, rebound index, static soil pressure coefficient and the like are calculated:
the initial void fraction of the sample should be calculated as follows:
Figure BDA0003321053790000081
in the formula, e0-initial porosity ratio, dimensionless;
w0-initial moisture content of the sample, dimensionless;
Gs-specific gravity, dimensionless, of rock or soil particles in the sample;
ρwdensity of water, g/cm3；
ρ0Density of the sample, g/cm3。
The unit settlement of the sample after solidification and stabilization under each pressure is calculated according to the following formula:
Figure BDA0003321053790000082
in the formula, Si-unit settling volume (mm/m) at a certain pressure;
h0-initial height of the specimen (mm);
Δhithe deformation (mm) of the sample after consolidation under a certain pressure.
The pore ratio of the sample after solidification and stabilization under each level of pressure is calculated according to the following formula:
Figure BDA0003321053790000083
the compressibility over a range of pressures is calculated as:
Figure BDA0003321053790000084
in the formula, av-compressibility factor (MPa)-1)；
piA certain pressure value (MPa).
The compressive modulus in a certain range of primary pressure is calculated as follows:
Figure BDA0003321053790000085
in the formula, Es-a compressive modulus (MPa) in a certain pressure range.
Compression index C within a certain pressure range of a stagecAnd rebound index CsIt should be calculated as follows:
Ccor
Figure BDA0003321053790000091
Without allowing lateral deformation, the soil sample is subjected to an axial pressure increase Δ σvWill cause a corresponding increase in lateral pressure Δ σhRatio delta sigmah/ΔσvCalled lateral pressure coefficient xi of soil or static soil pressure coefficient K0
Figure BDA0003321053790000092
When the settlement after construction in the filling area is calculated for the conventional soil, the settlement after construction in the filling area consists of three parts, one part is the compression deformation of the filling under the action of the self weight, the second part is the compression deformation of the stratum at the lower part of the filling under the action of the filling load, and the third part is the compression deformation of the filling and the foundation under the action of the load of the building (structure) at the upper part of the filling. Generally, the first portion compression set value is the largest and most difficult to obtain. The invention only carries out simulation and analysis on the first part, and the second part and the third part can refer to the existing research results.
Provides a method for calculating the filling deformation and stability of a large soil-rock mixed soil sample indoor compression instrument, applies pressure to a sample through an automatic control and recording device,
specifically, the overburden pressure of the soil body is calculated according to engineering conditions, the overburden pressure is used as a dead load to simulate long-term stacking, and the height change of the test sample is measured and recorded according to the following time sequence through an automatic control and recording device. The time is 6s, 30s, 1min, 2min, 10min, 30min, 1h, 2h, 3h, 4h, 8h and 24h, and 15/30 days are generally taken as the end time of the test. By plotting void ratio-time (logarithmic) curve (as shown in figure 3), after the main consolidation is completed, its secondary consolidation (compression) segment is similar to a straight line in at least one or two time logarithmic cycles, as shown by t1-t2The line segment of (2). The slope of this straight line segment is called the secondary consolidation coefficient.
The secondary consolidation coefficient is calculated as follows:
Figure BDA0003321053790000093
the secondary consolidation settlement is the settlement caused by creep deformation of the filling under the action of continuous load. If the post-construction settlement exceeds the influence of a building or equipment on the deformation of the foundation, an engineering accident is generated. Therefore, the partial settlement has the greatest influence on engineering, and is the key point of engineering attention. The compression of the filling soil itself in the post-construction settlement is mainly generated due to the secondary consolidation. The post-construction consolidation compression calculation is schematically shown in FIG. 4.
And calculating the deposition amount of the conventional soil sample generated by the secondary consolidation after the primary consolidation is completed through the following formula:
Figure BDA0003321053790000094
Figure BDA0003321053790000101
in the formula, Ss-creep compression of the fill itself;
hi-thickness of the ith soil layer;
e0i-the porosity ratio at the beginning of the i-th layer post-earthworking settlement timing;
e1i-the porosity ratio at the end of the main consolidation settlement of the ith layer of soil under overburden loading;
t1-is the time at which the primary consolidation settlement of the ith layer of soil under the action of the overburden load is finished;
t1' - - -is the time at which the post-construction settlement timer begins;
Cai-secondary consolidation coefficient of the i-th layer of soil under the action of overburden;
t-the time of settlement after construction is equal to the engineering design age, and 50 years are taken;
lambda-correction factor, taken as 1 without experience.
Wherein the pore ratio e of the sample after consolidation and stabilization under each stage of pressureiThe porosity e of the i-th layer soil at the end of the main consolidation settlement under the action of the overburden load can be further determined by the following formula1i：
Figure BDA0003321053790000102
And
Figure BDA0003321053790000103
in the formula, ei-the void ratio of the sample after consolidation and stabilization at each stage of pressure; e.g. of the type0-initial porosity ratio, dimensionless; w is a0-initial moisture content of the sample, dimensionless; gs-specific gravity, dimensionless, of rock or soil particles in the sample; rhowDensity of water, g/cm3；ρ0Density of the sample, g/cm3；h0-initial height of the specimen (mm); Δ hi-the deformation (mm) of the sample after consolidation stabilization at a certain level of pressure;
wherein C isaThe slope of the void ratio versus time (log) curve at each stage of pressure can be determined by the following equation:
Figure BDA0003321053790000104
and the unit sedimentation amount S after the sample is stably solidified at each stage of pressurei(mm/m) is calculated by the formula
Figure BDA0003321053790000105
And the compression coefficient a in a certain pressure range can be further obtained by the porosity ratio of the sample after the consolidation is stable under all levels of pressurev(MPa-1) Is calculated by the formula
Figure BDA0003321053790000111
In the formula piIs a pressure value (MPa) of a certain level,
further, a compression modulus E in a certain order of pressure ranges(MPa) is as follows
Figure BDA0003321053790000112
And, a compressibility index C over a range of pressurescAnd rebound index CsIs calculated by the formula
CcOr
Figure BDA0003321053790000113
In one embodiment, as shown in fig. 1-2, a humidifying or soaking test is performed on a sample by the compression apparatus of the present invention, and an additional settlement calculation generated by the humidifying or soaking is performed, before the test, remolded soil is prepared in the large-sized cutting ring 25 according to the dry density and the water content required by the test, permeable steel plates are placed above and below the sample, and after the automatic control and recording device 3 sets the required loading pressure, vertical pressure is applied to the sample by the jack 11 above the sample. And after the soil sample is stably compressed and deformed, humidifying or soaking the sample according to the designed water content. The method comprises the following specific steps:
(1) the cutting ring 25 is arranged in the protective ring 26, the sample 32 is arranged in the cutting ring 25, thin filter paper, an upper permeable steel plate 23 and a pressurizing cover plate 27 are sequentially arranged on the sample 32 and are placed in the middle of a pressurizing frame, the pressurizing cover plate 27 is aligned with the center of the frame, and the displacement sensor 12 is arranged;
(2) applying a pre-pressure of 1kPa to enable the sample to be in contact with the upper and lower parts of the instrument, and adjusting the pressure sensor 8 to measure and read an initial reading;
(3) determining the pressure to be applied according to the overburden pressure and the additional pressure of the upper structure, measuring and reading the displacement value of the displacement sensor 12 every 1 hour, and when the deformation is less than or equal to 0.01mm/h, determining that the deformation of the sample 32 is stable;
(4) when the pressure of the sample 32 is kept unchanged after deformation and stability, adding distilled water which is calculated to be added according to humidification into the quantitative humidifier 14, closing the water inlet valve 20 and the water discharge valve 29, opening the humidification valve 15, opening the humidification air pump 16 and the air pump valve 17, opening the exhaust valve 31, opening the quantitative humidifier 14, and humidifying the sample 32 until the water amount in the quantitative humidifier 14 is zero; when the water is required to be saturated, the quantitative humidifier 14 and the humidifying valve 16 are closed, the water inlet pipe 19, the water inlet valve 20 and the water discharge valve 29 are opened, and water is injected into the water inlet pipe 19 until the water is discharged from the water discharge pipe 30;
(4) after humidification or soaking, the displacement sensor 12 is measured and read every 1 hour, and when the deformation is less than or equal to 0.01mm/h, the deformation of the sample 32 is considered to be stable. And after the test is finished, dismantling the instrument.
Accordingly, by applying pressure to the sample 32 by the automatic control and recording device 3, after the compression deformation of the sample is stabilized, the sample is humidified or immersed by the quantitative humidifier 14 or the water inlet tube 19, the value of the displacement sensor 12 is read, and the amount of additional deposition of the sample after the sample is humidified or immersed by water is calculated by the following formula:
Figure BDA0003321053790000121
in the formula,. DELTA.s-additional settlement (mm) of the fill sample; deltasi-additional compressibility of the i-th layer of soil; h isi-thickness of the i-th layer of soil (mm); alpha-correction coefficient considering the stress state of foundation soil under the substrate, the region and other factors;
wherein the additional compressibility delta is the degree of compression at which the sample is humidified or soaked at a certain pressuresCalculated by the following formula:
Figure BDA0003321053790000122
in the formula, deltas-additional compressibility of the sample at a certain level of pressure; h isp-height (mm) after deformation stabilization before sample humidification; h isp' - - -height (mm) after stabilization of deformation after humidification of the sample, i.e., at a certain water content; h is0-initial height of the sample (mm).
In addition, one basic assumption of the static soil pressure coefficient is that the lateral deformation of the soil body is 0, namely the soil body is in a one-dimensional compression state. The sample meets the requirement that the lateral deformation is 0 in the test process of the consolidometer, so the vertical pressure and the horizontal lateral pressure of the sample in the compression process are respectively measured, and then the relation curve sigma between the vertical pressure and the horizontal pressure of each stage is obtainedv～σhThe lateral pressure coefficient K is determined based on the static soil pressure coefficient definition0Value (i.e. Δ σ)h/ΔσvRatio of (d). Meanwhile, as shown in fig. 5, these test points correspond to moire circles in different stress states, which are tangent to the same straight line. This line may be referred to as the side envelope e. The dip angle of the side-limiting envelope e is the excitation angle phimobAnd in fig. 5, the inclination of the intensity envelope f, i.e. the internal friction angle, is phi, where K of the intensity envelope is determinedaCalculating formula for active soil pressure coefficient
Figure BDA0003321053790000123
In fig. 5, the abscissa represents the positive stress, and the ordinate represents the shear stress. Obviously, the excitation angle phimobLess than the internal friction angle phi.
Thus, in one embodiment, when the automatic control and loading device 3 applies pressure to the sample 32, the vertical pressure σ is measured by the pressure sensor 8 and the pressure cell 24, respectivelyvAnd horizontal pressure σhThe side limit envelope line e is prepared by the Morer circles under different stress states, and the excitation angle is phimobThe internal friction angle corresponding to the soil body strength envelope line f is phi;
coefficient of static soil pressure K0Is Δ σhAnd Δ σvIs given by the formula
Figure BDA0003321053790000131
The known formula of the coefficient of the static soil pressure is
K01-sin phi, which is a theoretical formula of 1944 simplified by Jaky in 1948, and a side pressure coefficient formula of a currently common semi-empirical semi-theory is obtained;
the right sides of the formulas of the two static soil pressure coefficients are equal to obtain phi and phimobThe relationship between them is:
Figure BDA0003321053790000132
when phi and phimobBetweenWhen the relation of (A) is more than or equal to 30 DEG and less than or equal to 45 DEG, the obtained product can be obtained
φ＝φmob+11.5°，
When phi is more than or equal to 20 degrees and less than or equal to 45 degrees, the relation can be simplified into
φ＝1.18φmob+6.66 °; the relation is the internal friction angle phi and the excitation angle phimobAn approximate relationship therebetween;
and, the internal friction angle phi and the excitation angle phimobCan also be expressed as:
Figure BDA0003321053790000133
(Simpson is based on BRICK type) or 1.56 φmob(Federico et al, through statistical analysis of 59 actually measured static soil pressures, find the internal friction angle φ and the excitation angle φmobThe relational expression (c).
According to the invention, an automatic control and recording device is used to simulate continuous load, so that the compression deformation of the filling soil under the action of the automatic control and recording device can be obtained, and further the conventional soil sample filling area can be obtained to be settled; and the quantitative humidifier, the water inlet device, the water discharge device, the permeable steel plate and other devices are additionally arranged to increase the quantitative humidifying function of the sample, so that the settlement of accessories generated after the filling is humidified or soaked can be simulated; the invention is additionally provided with the pressure box to increase the test function of the lateral limit annular pressure of the sample, can obtain the lateral pressure coefficient (static soil pressure coefficient) of the mixture, further obtains the excitation angle and the internal friction angle through theoretical analysis, and can provide parameters for foundation pit support and side slope design of the soil filling area.

Claims (10)

1. The indoor compression instrument for the large soil-rock mixed soil sample is characterized by comprising a loading and testing system (1) and a sample containing device (2), wherein the sample containing device (2) comprises a retaining ring (26) for containing a sample, a quantitative humidifier (14) connected with the sample, and a plurality of pressure boxes (24) arranged along the circumferential direction of the sample; the loading and testing system (1) comprises a jack (11) pressurized at the top of the sample, an automatic control and recording device (3) in control connection with the jack, a pressure sensor (8) in two-way connection with the automatic control and recording device (3), and a plurality of displacement sensors (12) arranged at the top of the sample.
2. The large soil-rock mixing soil sample indoor compression instrument according to claim 1, wherein a base (21) is further disposed at a lower portion of the retaining ring (26), the base (21) and the retaining ring (26) enclose an accommodating space with an open top, and in the accommodating space: the inner wall of the retaining ring (26) is provided with a cutting ring (25), the sample is arranged in the cutting ring (25), the pressure box (24) is arranged between the sample and the cutting ring (25), an upper permeable steel plate (23) and a lower permeable steel plate (22) are respectively arranged above and below the sample, and a pressurizing cover plate (27) is arranged above the upper permeable steel plate (23).
3. The large soil-rock mixed soil sample indoor compression instrument as claimed in claim 2, wherein a water inlet pipe (19) and a humidifying pipe (18) are respectively connected and arranged below the lower water permeable steel plate (22), and the quantitative humidifier (14) is arranged on the humidifying pipe (18); and a drain pipe (28) and an exhaust pipe (30) are respectively connected and arranged above the upper water permeable steel plate (23), and the exhaust pipe (30) is communicated with the humidifying pipe (18).
4. The large-scale soil-rock mixing soil sample indoor compression instrument according to claim 2, wherein the jack (11) is carried by a two-column loading frame (10), and the jack (11) is pressed on the pressing cover plate.
5. A method for calculating the deformation and stability of the filled soil obtained by the indoor compression meter for large soil-rock mixture soil samples according to the claims 1-4, characterized in that the automatic control and recording device (3) applies pressure to the samples, and the deposition amount of the conventional soil samples generated by the secondary consolidation after the primary consolidation is completed is calculated by the following formula:
Figure FDA0003321053780000011
Figure FDA0003321053780000012
in the formula, Ss-creep compression of the fill itself;
hi-thickness of the ith soil layer;
e0i-the porosity ratio at the beginning of the i-th layer post-earthworking settlement timing;
e1i-the porosity ratio at the end of the main consolidation settlement of the ith layer of soil under overburden loading;
t1-is the time at which the primary consolidation settlement of the ith layer of soil under the action of the overburden load is finished;
t1' - - -is the time at which the post-construction settlement timer begins;
Cai-secondary consolidation coefficient of the i-th layer of soil under the action of overburden;
t-the time of the post-construction settlement;
lambda-correction factor, taken as 1 without experience.
6. The method for calculating deformation and stability of filled soil according to claim 5, wherein the pore ratio e of the sample after consolidation stabilization at each stage of pressureiThe porosity e of the i-th layer soil at the end of the main consolidation settlement under the action of the overburden load can be further determined by the following formula1i：
Figure FDA0003321053780000021
And
Figure FDA0003321053780000022
in the formula, ei-the void ratio of the sample after consolidation and stabilization at each stage of pressure; e.g. of the type0-initial porosity ratio, dimensionless; w is a0Initial water content of the sample, no amountA head line; gs-specific gravity, dimensionless, of rock or soil particles in the sample; rhowDensity of water, g/cm3；ρ0Density of the sample, g/cm3；h0-initial height of the specimen (mm); Δ hi-the deformation (mm) of the sample after consolidation stabilization at a certain level of pressure;
wherein C isaThe slope of the void ratio versus time (log) curve at each stage of pressure can be determined by the following equation:
Figure FDA0003321053780000023
and the unit sedimentation amount S after the sample is stably solidified at each stage of pressurei(mm/m) is calculated by the formula
Figure FDA0003321053780000024
7. The method for calculating deformation and stability of filled soil according to claim 6, wherein the compression coefficient a within a certain pressure range can be further obtained by the porosity ratio of the sample after consolidation and stabilization at each pressure levelv(MPa-1) Is calculated by the formula
Figure FDA0003321053780000031
In the formula piIs a pressure value (MPa) of a certain level,
further, a compression modulus E in a certain order of pressure ranges(MPa) is as follows
Figure FDA0003321053780000032
And, a compressibility index C over a range of pressurescAnd rebound index CsIs calculated by the formula
CcOr
Figure FDA0003321053780000033
8. The filling deformation and stability calculation method according to claim 5, wherein the automatic control and recording device (3) applies pressure to the sample, after the compressive deformation of the sample is stabilized, the sample is humidified or soaked by the quantitative humidifier (14) or the water inlet pipe (19), the value of the displacement sensor (12) is read, and the additional deposition amount of the sample after being humidified or soaked is calculated by the following formula:
Figure FDA0003321053780000034
in the formula,. DELTA.s-additional settlement (mm) of the fill sample; deltasi-additional compressibility of the i-th layer of soil; h isi-thickness of the i-th layer of soil (mm); alpha-correction coefficient considering the stress state of foundation soil under the substrate, the region and other factors;
wherein at a certain pressure the additional compressibility factor delta of the samplesCalculated by the following formula:
Figure FDA0003321053780000035
in the formula, deltas-additional compressibility of the sample at a certain level of pressure; h isp-height (mm) after deformation stabilization before sample humidification; h isp' - - -height (mm) after stabilization of deformation after humidification of the sample, i.e., at a certain water content; h is0-initial height of the sample (mm).
9. The method for calculating deformation and stability of filling soil according to claim 5, wherein when the automatic control and loading device (3) applies pressure to the sample, the pressure sensor (8) and the pressure cell (24) measure the pressure respectivelyTo obtain vertical pressure sigmavAnd horizontal pressure σhThe side limit envelope curve is prepared by the Morer circles under different stress states, and the excitation angle is phimobThe internal friction angle corresponding to the soil body strength envelope line is phi; coefficient of static soil pressure K0Is Δ σhAnd Δ σvIs given by the formula
Figure FDA0003321053780000041
The known formula of the coefficient of the static soil pressure is
K0＝1-sinφ，
The right sides of the formulas of the two static soil pressure coefficients are equal to obtain phi and phimobThe relationship between them is:
Figure FDA0003321053780000042
10. the method of claim 9, wherein phi and phi are calculatedmobWhen the relation between the two is more than or equal to 30 degrees and less than or equal to 45 degrees, the obtained product can be obtained
φ＝φmob+11.5°，
When phi is more than or equal to 20 degrees and less than or equal to 45 degrees, the relation can be simplified into
φ＝1.18φmob+6.66°；
And, the internal friction angle phi and the excitation angle phimobCan also be expressed as:
Figure FDA0003321053780000043
or phi is 1.56 phimob。
CN202111246175.7A 2021-10-26 2021-10-26 Large-scale soil-rock mixed soil sample indoor compression instrument and filling deformation and stability calculation method Pending CN114018700A (en)

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