CN107219132B - Simplified determination method for shear strength of bentonite waterproof blanket and geomembrane composite lining - Google Patents
Simplified determination method for shear strength of bentonite waterproof blanket and geomembrane composite lining Download PDFInfo
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- CN107219132B CN107219132B CN201710395843.XA CN201710395843A CN107219132B CN 107219132 B CN107219132 B CN 107219132B CN 201710395843 A CN201710395843 A CN 201710395843A CN 107219132 B CN107219132 B CN 107219132B
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- shear strength
- sodium bentonite
- waterproof blanket
- bentonite waterproof
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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
Abstract
The invention discloses a simplified determination method of the shear strength of a sodium bentonite waterproof blanket and a geomembrane composite lining, which relates to the technical field of environmental rock and soil, in particular to the determination of the shear strength of a needled sodium bentonite waterproof blanket and a geomembrane composite lining at the bottom of a landfill and the calculation of the slope stability; the method for determining the shearing strength of the needled sodium bentonite waterproof blanket and the geomembrane composite lining, which is disclosed by the invention, is characterized by comprising the following steps of: determining the shear strength of the needled sodium bentonite waterproof blanket and the geomembrane composite lining as a whole; the peak shear strength and residual shear strength of the composite liner were quantitatively estimated using the shear strength of sodium bentonite. The method is simple and easy to implement, and has low requirements on a test device; the shear strength estimate of the composite lining is safer.
Description
Technical Field
The invention belongs to the technical field of environmental rock and soil, and particularly relates to a simplified determination method of shear strength of a bentonite waterproof blanket and a geomembrane composite lining when the bentonite waterproof blanket and the geomembrane composite lining are used for slope stability analysis.
Background
The needled sodium bentonite waterproof blanket (GCL) and the Geomembrane (GM) are often used as anti-seepage structures in engineering, the two contact with each other to form a good composite anti-seepage structure layer, and the friction characteristics of the internal interface of the needled GCL after hydration and the contact interface of the GCL and the geomembrane are very important indexes for maintaining the stability of a side slope. Shear strength is commonly used in engineering applications to characterize the frictional characteristics of the needled GCL internal interface and the GCL-geomembrane contact interface, and the shear strength of the needled GCL internal interface and the GCL-geomembrane contact interface is often obtained by large-scale shear tests.
General detection mechanisms and enterprises lack large-scale shearing test equipment, the hydration process of the sodium bentonite waterproof blanket is slow, and a group of tests need to be prepared for 3-4 days, so that the efficiency of carrying out related strength tests is very low.
The shearing failure surfaces of the needled sodium-based bentonite waterproof blanket and geomembrane composite lining structure under different normal pressures can be changed, and higher safety factor can be obtained by adopting the internal shearing strength of the needled GCL or the contact interface strength of the GCL and the geomembrane to perform slope stability analysis, so that the engineering safety is not facilitated.
The slope stability analysis is carried out by adopting the integral shear strength of the needled sodium bentonite waterproof blanket and the geomembrane composite lining, so that the integral friction performance of the slope is reflected more truly, the calculation workload is reduced, and the slope stability analysis method has better application prospect.
Disclosure of Invention
The invention aims to solve the problems and provides a simple, practical, safe and reliable method for determining the shear strength of a needled sodium bentonite waterproof blanket and a geomembrane composite lining.
The technical solution of the invention is as follows:
a simplified method for determining the shear strength of a bentonite waterproof blanket and geomembrane composite liner, comprising the steps of:
(1) taking sodium bentonite inside the sodium bentonite waterproof blanket to perform hydration saturation shear strength test, and obtaining the peak shear strength tau of the sodium bentonite in the bentonite waterproof blanket through the testb；
(2) Estimating the peak shear strength tau of the sodium bentonite waterproof blanket and the geomembrane composite lining by utilizing the relation between the peak strength of the hydrated bentonite and the integral shear strength of the sodium bentonite waterproof blanket and the geomembrane composite liningp；
(3) Estimation of residual shear strength tau of sodium bentonite waterproof blanket and geomembrane composite lining using residual strength of hydrated bentoniterThe method is used for calculating the slope stability of the sodium-containing bentonite waterproof blanket and the geomembrane composite lining.
Specifically, the sodium bentonite in the sodium bentonite waterproof blanket obtained in the step (1) is subjected to a hydration saturation shear strength test, and the specific operation steps are as follows:
1) preparing a soil sample from the sodium bentonite according to the liquid limit water content;
2) filling a soil sample into an earth-engineering direct shear apparatus, properly filling a bentonite sample in consideration of the pressurized consolidation settlement, and then adding water into a shear box for saturation;
3) pressurizing to test pressure, solidifying for 2 days, or observing stable sedimentation, wherein the test pressure is 25 kPa, 50 kPa, 100 kPa and 200kPa respectively;
4) the shearing rate is controlled below 0.1 mm/min;
5) obtaining an internal friction angle phi according to the fitting of the test peak intensity envelopebThe size of (d);
6) neglecting cohesive force of the hydrated bentonite, the peak intensity of the hydrated bentonite is estimated to be tau according to the following formulab＝σn*tanφbWhere σ isnIs the normal pressure.
Specifically, in the step (2), the peak shear strength τ of the sodium bentonite waterproof blanket and the geomembrane composite lining ispWith peak shear strength tau of hydrated bentonitebThe relationship of (1) is: tau isp＝n*τbAnd n is a constant of 1.4 to 1.6.
Specifically, in the step (3), the residual shear strength τ of the sodium bentonite waterproof blanket and the geomembrane composite lining isrAccording to linear expression τr＝cr+σn*tanφrCalculation of where σnFor normal pressure, take cr＝0，φr＝5°。
Whether the final shear failure plane of the needled sodium bentonite waterproof blanket + geomembrane composite liner occurs inside the GCL or at the interface where the geomembrane contacts the GCL, the residual shear strength of the hydrated bentonite represents the lower limit of the composite liner shear strength. Therefore, the integral residual shear strength tau of the needled sodium bentonite waterproof blanket and the geomembrane composite liningrAccording to linear expression τr＝cr+σn*tanφrAnd (4) calculating. The residual strength of the hydrated bentonite can be estimated by adopting empirical strength, and c is takenr＝0，φr＝5°。
Specifically, in the simplified determination method for shear strength of the bentonite waterproof blanket and geomembrane composite lining, the peak shear strength of the sodium bentonite waterproof blanket and the geomembrane composite lining is selected at the position of a bottom slope with a small gradient of the landfill, and the residual shear strength of the sodium bentonite waterproof blanket and the geomembrane composite lining is selected at the position of a slope with a large gradient.
The invention has the beneficial effects that: the strength measuring and determining method is simple and easy to implement, has low requirements on a test device, has short detection time, and saves manpower and material resources; and the estimated value of the shear strength of the composite lining is safe, and the measured data is safe and reliable.
Drawings
FIG. 1 is a schematic diagram of shearing of sodium hydrate-based bentonite;
FIG. 2 is a shear stress displacement curve of hydrated sodium bentonite;
FIG. 3 is a plot of the peak strength envelope of the hydrated sodium bentonite;
FIG. 4 is the integral shear peak strength of the needled bentonite waterproof blanket + geomembrane composite liner;
fig. 5 is the overall shear residual strength of the needled bentonite waterproof blanket + geomembrane composite liner.
Detailed Description
A simplified determination method for the shearing strength of a needled sodium bentonite waterproof blanket and a geomembrane composite lining comprises the following steps:
(1) the test obtains the peak value shear strength tau of the hydrated sodium bentonite in the bentonite waterproof blanketb
Taking sodium bentonite in GCL to perform hydration saturation shear strength test, wherein the test equipment adopts a geotechnical direct shear apparatus, and the specific details are operated according to the following process:
1) preparing a soil sample from the sodium bentonite according to the liquid limit water content;
2) loading the soil sample into a direct shear apparatus (as shown in figure 1), properly filling bentonite sample in consideration of the consolidation settlement after pressurization, and adding water into a shear box for saturation;
3) pressurizing to test pressure, solidifying for 2 days, or observing stable sedimentation, wherein the test pressure is 25 kPa, 50 kPa, 100 kPa and 200kPa respectively;
4) the shearing rate is controlled below 0.1mm/min, and the obtained stress-displacement relation curve is shown in figure 2;
5) neglecting cohesive force of the hydrated bentonite, and obtaining an internal friction angle phi according to the test peak intensity envelope fittingbAs shown in fig. 3;
6) arbitrary normal pressure hydrolysisThe peak shear strength of the bentonite is estimated asb＝σn*tanφb。
(2) Integral shear peak intensity tau of needled sodium bentonite waterproof blanket and geomembrane composite liningpMethod of determining
Expression of tau by a linear relationshipp＝n*τbThe method is simplified to obtain the integral peak shear strength (tau) of the needled sodium bentonite waterproof blanket and the geomembrane composite liningp) And n is a constant of 1.4 to 1.6. The value of the constant n is related to the normal pressure (as shown in fig. 4), and the most conservative value of n is 1.4.
(3) Integral residual shear strength tau of needled sodium bentonite waterproof blanket and geomembrane composite liningrMethod of determining
The residual shear strength of the hydrated bentonite represents the lower limit of the shear strength of the composite lining, and the integral residual shear strength tau of the needled sodium bentonite waterproof blanket and the geomembrane composite liningrAccording to linear expression τr＝cr+σn*tanφrAnd (4) calculating. The residual strength of the hydrated bentonite can be estimated by adopting empirical strength, and c is takenr＝0，φ r5 ° (see fig. 5).
Claims (5)
1. A simplified determination method for the shearing strength of a sodium bentonite waterproof blanket and a geomembrane composite lining is characterized by comprising the following steps: comprises the following steps:
(1) taking sodium bentonite inside the sodium bentonite waterproof blanket to perform hydration saturation shear strength test, and obtaining the peak shear strength tau of the sodium bentonite in the bentonite waterproof blanket through the testb；
(2) Estimating the peak shear strength tau of the sodium bentonite waterproof blanket and the geomembrane composite lining by utilizing the relation between the peak strength of the hydrated bentonite and the integral shear strength of the sodium bentonite waterproof blanket and the geomembrane composite liningp；
(3) Estimation of residual shear strength tau of sodium bentonite waterproof blanket and geomembrane composite lining using residual strength of hydrated bentoniterSlope stability for sodium bentonite-containing water-proof blanket and geomembrane composite liningAnd (4) calculating.
2. The simplified determination method for shear strength of sodium bentonite waterproof blanket and geomembrane composite lining according to claim 1, characterized in that, in the step (1), the sodium bentonite inside the sodium bentonite waterproof blanket is subjected to hydration saturation shear strength test, and the specific operation steps are as follows:
1) preparing a soil sample from the sodium bentonite according to the liquid limit water content;
2) filling a soil sample into an earth-engineering direct shear apparatus, properly filling a bentonite sample in consideration of the pressurized consolidation settlement, and then adding water into a shear box for saturation;
3) pressurizing to test pressure, solidifying for 2 days, or observing stable sedimentation, wherein the test pressure is 25 kPa, 50 kPa, 100 kPa and 200kPa respectively;
4) the shearing rate is controlled below 0.1 mm/min;
5) obtaining an internal friction angle phi according to the fitting of the test peak intensity envelopebThe size of (d);
6) neglecting cohesive force of the hydrated bentonite, the peak intensity of the hydrated bentonite is estimated to be tau according to the following formulab＝σn*tanφbWhere σ isnIs the normal pressure.
3. The simplified method for determining the shear strength of a sodium bentonite waterproof blanket and a geomembrane composite liner according to claim 1, wherein in the step (2), the sodium bentonite waterproof blanket and the geomembrane composite liner have a peak shear strength τpWith peak shear strength tau of hydrated bentonitebThe relationship of (1) is: tau isp＝n*τbAnd n is a constant of 1.4 to 1.6.
4. The simplified method for determining shear strength of sodium bentonite waterproof blanket and geomembrane composite lining as claimed in claim 1, wherein in said step (3), the residual shear strength τ of the sodium bentonite waterproof blanket and geomembrane composite lining isrAccording to linear expression τr＝cr+σn*tanφrCalculation of where σnFor normal pressure, take cr＝0，φr＝5°。
5. The method of claim 1, wherein the peak shear strength of the sodium bentonite waterproof blanket and geomembrane composite liner is selected at a site on a bottom slope of the landfill, and the residual shear strength of the sodium bentonite waterproof blanket and geomembrane composite liner is selected on the slope.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2265824C1 (en) * | 2004-04-26 | 2005-12-10 | Хрусталев Евгений Николаевич | Method of determining permissible contact strength of soil base |
| CN101986130A (en) * | 2010-09-06 | 2011-03-16 | 水利部交通运输部国家能源局南京水利科学研究院 | Triaxial test method for shear strength property of weak layer |
| CN201817824U (en) * | 2010-10-19 | 2011-05-04 | 浙江大学 | Antiseepage liner for bottom side slope of refuse landfill |
| CN102507340A (en) * | 2011-10-21 | 2012-06-20 | 同济大学 | Interlaminar shear strength parameter determination method of combined type pavement system |
| CN104634669A (en) * | 2015-03-12 | 2015-05-20 | 太原理工大学 | Detection method for soil shear strength index |
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- 2017-05-31 CN CN201710395843.XA patent/CN107219132B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2265824C1 (en) * | 2004-04-26 | 2005-12-10 | Хрусталев Евгений Николаевич | Method of determining permissible contact strength of soil base |
| CN101986130A (en) * | 2010-09-06 | 2011-03-16 | 水利部交通运输部国家能源局南京水利科学研究院 | Triaxial test method for shear strength property of weak layer |
| CN201817824U (en) * | 2010-10-19 | 2011-05-04 | 浙江大学 | Antiseepage liner for bottom side slope of refuse landfill |
| CN102507340A (en) * | 2011-10-21 | 2012-06-20 | 同济大学 | Interlaminar shear strength parameter determination method of combined type pavement system |
| CN104634669A (en) * | 2015-03-12 | 2015-05-20 | 太原理工大学 | Detection method for soil shear strength index |
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