CN107884285B - Soil shear strength parameter test method based on critical edge pressure formula - Google Patents
Soil shear strength parameter test method based on critical edge pressure formula Download PDFInfo
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- CN107884285B CN107884285B CN201711092734.7A CN201711092734A CN107884285B CN 107884285 B CN107884285 B CN 107884285B CN 201711092734 A CN201711092734 A CN 201711092734A CN 107884285 B CN107884285 B CN 107884285B
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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
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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- 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
- G01N2203/0014—Type of force applied
- G01N2203/0025—Shearing
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- 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
- G01N2203/003—Generation of the force
- G01N2203/0042—Pneumatic or hydraulic means
- G01N2203/0044—Pneumatic means
Abstract
The invention discloses a kind of soil shear strength parameter test methods based on critical edge pressure formula, and the shear strength parameter of the soil body can accurate, quickly, be economically tested out by this method.Carry out loading plate load test, loading plate two sides apply two different earth's surface load q1、q2Value, according to different earth's surface load q1、q2Value tests out critical edge pressure p respectivelycr1、pcr2Value, goes out soil body cohesive strength c value, soil body internalfrictionangleφ value by pcr formula inverse.
Description
Technical field
The present invention relates to a kind of soil shear strength parameter test methods, specifically a kind of public with critical edge pressure
Formula, by loading plate load test, the method for testing out soil shear strength parameter.
Background technique
Soil shear strength parameter, i.e. cohesive strength c and internalfrictionangleφ are most important two mechanics parameters of the soil body, work
It includes laboratory test and outdoor test (test in situ), laboratory test that the test of the shear strength parameter of the soil body is tested in journey
Including direct shear test, triaxial compression test and unconfined compression strength test；Compared with laboratory test, test in situ
The soil body is not disturbed, therefore has more engineering superiority, especially for the soil that sampling is difficult, test in situ is even more can not
Substitution, the in-situ test for testing soil shear strength parameter at present mainly includes vane shear test, large-scale direct shearing examination
It tests, vane shear test is used to measure the undrained shear strength of saturated soft clay (φ ≈ 0), and large-scale direct shear test is not
(test that need to do three kinds of different vertical pressures can just obtain one group of c, φ value) only at high cost, and as indoor direct shear test
There are inherent defects: shear surface artificially limits, shearing stress distribution is uneven, shear surface is gradually reduced, at present the examination of large size direct shearing
It tests for testing coarse granule soil classifiction.There is presently no better test in situ can accurately, quickly, economically
Test out the shear strength parameter of the soil body, it is therefore desirable to develop new test method.
Summary of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of soil body shearing resistances based on critical edge pressure formula
Intensive parameter test method can accurate, quickly, economically test out the shear strength parameter of the soil body by this method.
The object of the present invention is achieved like this:
A kind of soil shear strength parameter test method based on critical edge pressure formula,
Under vertical pressure effect, mecystasis is initially entered at strip footing basal edge, according to strip footing ground
Critical edge pressure pcr formula:
In formula, q is vertical stress caused by soil body self weight at basic bottom surface, and c is soil body cohesive strength, and φ is to rub in the soil body
Angle；
Carry out load test, loading plate two sides apply two different earth's surface load q1、q2Value, according to q1、q2It tests respectively
Pcr out1、pcr2Value, c, φ value of the soil body are gone out by pcr formula inverse:
In formula,
Further, load test is carried out using the loading plate of bar shaped, does not apply surface load in the side of loading plate, i.e.,
q1=0, and apply surface load q in the other side2, a load test tests out c, φ value of the soil body.
Further, the loading plate includes plate body and the branch for being used to transmit vertical pressure that plate body upper end is arranged in
Seat, the lower section of the loading plate are equipped with the air bag for uniformly transferring vertical pressure, the air bag in a rectangular parallelepiped shape, the air bag
Upper surface, lower surface shape is identical as the shape of loading plate and corresponding installation, be equipped in inside air bag for testing gas
The first displacement sensor, second displacement sensor, the third displacement sensor of intracapsular portion's thickness change form load test dress
It sets, the first displacement sensor is mounted on the side that loading plate does not apply surface load, and third displacement sensor is mounted on loading plate
Apply surface load q2Side, the second displacement sensor is located at the first displacement sensor, in third displacement sensor
Between.
In order to guarantee the stress distribution at loading plate center close to strip load, further, the length of the loading plate
Wide ratio is greater than 3.
Further, first displacement sensor, second displacement sensor, third displacement sensor are respectively positioned on loading plate
On middle line.
Further, this method realizes that steps are as follows:
Step 1: load test device is placed on the test soil body；
Step 2: applying size in the side of loading plate is q2Surface load；
Step 3: applying vertical pressure P on the support of loading plate, in vertical pressure P and air bag air pressure p meet P=A ×
P, A indicates capsule floor space in formula, is bonded air bag bottom surface with foundation soil surface；
Step 4: it is measured under different vertical pressure P effects respectively, the shift value δ of the first displacement sensor6, second displacement pass
The shift value δ of sensor7, third displacement sensor shift value δ8；
Step 5: p- Δ is made respectively76With p- Δ78Curve, wherein Δ76=δ7- δ6,Δ78=δ7- δ8；
Step 6: p- Δ76With p- Δ78The atmospheric pressure value p of the decline turning point of curve subtracts corresponding surface load value and is
The p of the soil bodycr1、pcr2It is worth, then goes out c, φ value of the soil body by pcr formula inverse.
By adopting the above-described technical solution, the invention has the following beneficial effects:
Based on critical edge pressure formula, the shear strength parameter of the soil body can be tested out by loading plate load test.Face modeling
Load Formula is to derive in strict accordance with theory of mechanics, therefore test result is accurate；Pass through a loading plate load test
C, φ value can be obtained, therefore test process is quick；Test is not necessarily to expensive instrument, requires also not testing crew operative skill
Height, therefore testing cost economy.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of load test device；
Fig. 2 is the schematic diagram for applying earth's surface load；
Fig. 3 is the schematic diagram for applying vertical pressure；
Fig. 4 is p- Δ76With p- Δ78Curve graph.
Appended drawing reference
In attached drawing, 1 is loading plate, and 2 be steel plate, and 3 be air bag, and 4 be support, and 5 be pump stomata, and 6 be the first displacement sensor,
7 be second displacement sensor, and 8 be third displacement sensor.
Specific embodiment
Theoretical analysis shows that initially entering mecystasis, native power at strip footing basal edge under vertical pressure effect
It learns teaching material and provides strip footing Critical Edge Pressure For Subsoil pcr formula, as shown in formula (1),
Q is vertical stress caused by soil body self weight at basic bottom surface in formula.
By formula (1) as it can be seen that Critical Edge Pressure For Subsoil pcrThere is direct corresponding relationship with cohesive strength c, the internalfrictionangleφ of soil, when
When carrying out load test using strip loading plate, according to strip loading plate short side two sides difference q (q1, q2) test out two
A pcr(pcr1, pcr2) value, c, φ value that can be unearthed by formula (1) inverse, calculation formula such as formula (2.1), shown in (2.2).
In formula,
It is used in formula (2.1), the derivation process of formula (2.2)
Load test is carried out using load test device, load test device includes loading plate, and the loading plate includes steel
Plate 2 (plate body), top hold-down support 4.Air bag 3 is set below steel plate 2, and 2 length-width ratio of steel plate is greater than 3, pump gas is provided on steel plate 2
Hole 5, in a rectangular parallelepiped shape, the upper surface of the air bag, the shape of lower surface are identical as the shape of loading plate and corresponding for the air bag
Installation, capsule floor space does not change in test process, can be used that application No. is 201610122281.7 scheme production, such as
Shown in attached drawing 1.Inside air bag 3, on the middle line of loading plate 1, it is equipped with the first displacement sensing respectively on left side, centre, right side
Device 6, second displacement sensor 7, third displacement sensor 8.Surface load can not be applied in the side of strip loading plate, i.e.,
q1=0, and apply surface load q in the other side2, such loading plate load test, which need to only carry out, can once test out c, φ.
The specific implementation steps are as follows for this method:
Step 1: load test device is placed on the test soil body；
Step 2: applying size on the right side of loading plate 1 is q2Surface load, as shown in Fig. 2.
Step 3: vertical pressure P is applied by jack on the support 4 of loading plate 1, while by pumping stomata 5 to air bag
Gas is pumped in 3, air pressure p in vertical pressure P and air bag 3 is made to meet P=A × p, and so control can guarantee air bag bottom surface and foundation soil
Surface is all in close contact.(note: when p is less than normal, shows to assume responsibility for excessive pressure at the support of air bag quadrangle, inflator should be passed through
Gas is pumped in air bag to increase air pressure, when p is bigger than normal, shows that capsule bottom is not fully pressed against on foundation soil, should be deflated by button
To reduce air pressure.) A indicates capsule floor space in formula, as shown in Fig. 3.
Step 4: measuring respectively under different vertical pressure P effect, the first displacement sensor 6, second displacement sensor 7, the
The shift value δ of triple motion sensor 86, δ7,δ8。
Step 5: p- Δ is made respectively76With p- Δ78Curve, wherein Δ76=δ7- δ6,Δ78=δ7- δ8.Certain test
In, q2=2kPa, obtained p- Δ76With p- Δ78Curve is as shown in Fig. 4.
Step 6: by taking the curve in attached drawing 4 as an example, curve p- Δ76Start to grow steadily, after p=88kPa, occur steep
Drop, shows that plastic failure occurs in the soil body of loading plate left bottom, therefore take pcr1=88kPa, curve p- Δ78Start steady
Rise, after p=100kPa, steep drop occurs, show that plastic failure occurs in the soil body of loading plate bottom right side, therefore take pcr2
=100-2=98kPa (2 table q in formula2=2kPa), while q1=0, total data substitutes into formula (2.1), and (2.2) can calculate c=
11.8kPa, φ=28.3 °.
Test data is as follows:
Finally, it is stated that preferred embodiment above is only used to illustrate the technical scheme of the present invention and not to limit it, although logical
It crosses above preferred embodiment the present invention is described in detail, however, those skilled in the art should understand that, can be
Various changes are made to it in form and in details, without departing from claims of the present invention limited range.
Claims (3)
1. a kind of soil shear strength parameter test method based on critical edge pressure formula, which is characterized in that
Under vertical pressure effect, mecystasis is initially entered at strip footing basal edge, modeling is faced according to strip footing ground
Load pcrFormula:
In formula, q is vertical stress caused by soil body self weight at basic bottom surface, and c is soil body cohesive strength, and φ is soil body internal friction angle；
Carry out load test, loading plate two sides apply two different earth's surface load q1、q2Value, according to q1、q2It tests out respectively
pcr1、pcr2Value, by pcrFormula inverse goes out c, φ value of the soil body:
In formula,
Load test is carried out using the loading plate of bar shaped, does not apply surface load, i.e. q in the side of loading plate1=0, and another
Side applies surface load q2, a load test tests out c, φ value of the soil body；
The loading plate include plate body and be arranged in plate body upper end for transmitting the support of vertical pressure, the loading plate
Lower section is equipped with air bag for uniformly transferring vertical pressure, the air bag in a rectangular parallelepiped shape, upper surface, the lower surface of the air bag
Shape is identical as the shape of loading plate and corresponding installation, be equipped in inside air bag for testing inside air bag thickness change
First displacement sensor, second displacement sensor, third displacement sensor form load test device, the first displacement sensor
It is mounted on the side that loading plate does not apply surface load, third displacement sensor is mounted on loading plate and applies surface load q2One
Side, the second displacement sensor are located at the centre of the first displacement sensor, third displacement sensor；
This method realizes that steps are as follows:
Step 1: load test device is placed on the test soil body；
Step 2: applying size in the side of loading plate is q2Surface load；
Step 3: applying vertical pressure P on the support of loading plate, and vertical pressure P meets P=A × p, formula with air pressure p in air bag
Middle A indicates capsule floor space, is bonded air bag bottom surface with foundation soil surface；
Step 4: it is measured under different vertical pressure P effects respectively, the shift value δ of the first displacement sensor6, second displacement sensor
Shift value δ7, third displacement sensor shift value δ8；
Step 5: p- Δ is made respectively76With p- Δ78Curve, wherein Δ76=δ7- δ6,Δ78=δ7- δ8；
Step 6: p- Δ76With p- Δ78It is the soil body that the atmospheric pressure value p of the decline turning point of curve, which subtracts corresponding surface load value,
pcr1、pcr2Value, then by pcrFormula inverse goes out c, φ value of the soil body.
2. the soil shear strength parameter test method according to claim 1 based on critical edge pressure formula, feature exist
In the length-width ratio of the loading plate is greater than 3.
3. the soil shear strength parameter test method according to claim 1 based on critical edge pressure formula, feature exist
In first displacement sensor, second displacement sensor, third displacement sensor are respectively positioned on loading plate middle line.
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Citations (4)
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|---|---|---|---|---|
| JP2014052301A (en) * | 2012-09-07 | 2014-03-20 | Mitsubishi Heavy Ind Ltd | Composite load testing method and specimen for composite load test |
| CN105714754A (en) * | 2016-03-04 | 2016-06-29 | 重庆科技学院 | Method for manufacturing airbag for plate loading test of foundation |
| CN105928803A (en) * | 2016-07-15 | 2016-09-07 | 中南大学 | Soil shear strength parameter in-situ test apparatus and test method thereof |
| CN106930335A (en) * | 2017-03-18 | 2017-07-07 | 辽宁工程技术大学 | A kind of foundation bearing capacity determines checking method |
-
2017
- 2017-11-08 CN CN201711092734.7A patent/CN107884285B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014052301A (en) * | 2012-09-07 | 2014-03-20 | Mitsubishi Heavy Ind Ltd | Composite load testing method and specimen for composite load test |
| CN105714754A (en) * | 2016-03-04 | 2016-06-29 | 重庆科技学院 | Method for manufacturing airbag for plate loading test of foundation |
| CN105928803A (en) * | 2016-07-15 | 2016-09-07 | 中南大学 | Soil shear strength parameter in-situ test apparatus and test method thereof |
| CN106930335A (en) * | 2017-03-18 | 2017-07-07 | 辽宁工程技术大学 | A kind of foundation bearing capacity determines checking method |
Non-Patent Citations (1)
| Title |
|---|
| 基于柔性承载板载荷试验的土抗剪强度参数反演研究;许年春，等;《岩土力学》;20180731;第39卷(第增刊1期);227-234 |
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