CN108414343A - A method of measuring sample rubber-oil-pipe sensor amount in coarse-grained soil Large-scale Triaxial Experiments - Google Patents

Abstract

A method of sample rubber-oil-pipe sensor amount in coarse-grained soil Large-scale Triaxial Experiments is measured, soil test technique field is belonged to.This measurement method is, small size confining pressure CYCLIC LOADING process is added in the experiment of conventional isotonic consolidation, measure when different confining pressures recoverable volume of sample variable quantity under the conditions of small size confining pressure increment, then it is recoverable feature to be based on rubber-oil-pipe sensor, realizes rubber-oil-pipe sensor amount and its measurement with confining pressure changing rule.The measurement method is easy to realize in normal triaxial instrument, operating procedure is simple, difficulty is low, and it may be coupled to during conventional consolidation test, do not influence follow-up test, avoiding some measurement methods needs separately development equipment and carries out multiple sample preparation, the link of multigroup experiment, and effectively eliminate the influence of sample individual discreteness, the embedded quantity that rubber membrane changes with confining pressure can be accurately measured, cubic deformation to correct triaxial test middle coarse grained soil sample provides reliable technological means, the research of coarse grain soil mechanics characteristic and constitutive model is pushed, with good promotional value.

Description

A method of measuring sample rubber-oil-pipe sensor amount in coarse-grained soil Large-scale Triaxial Experiments

Technical field

The present invention relates to a kind of methods of sample rubber-oil-pipe sensor amount in measurement coarse-grained soil Large-scale Triaxial Experiments, belong to geotechnique Experimental technique field.

Background technology

In triaxial test, confining pressure is transmitted on sample by rubber membrane.But it since specimen surface is uneven, applies Rubber membrane can be embedded into specimen surface inter-granular porosity after adding confining pressure, and embedded depth becomes with the variation of effective confining pressure Change, this phenomenon is rubber-oil-pipe sensor.In normal triaxial drained shear test, determine that the method that saturated sample body becomes is to survey The water of sample discharge or sucking is measured, but due to the influence of rubber-oil-pipe sensor so that body, which becomes to measure, contains rubber-oil-pipe sensor mistake Difference can not accurately reflect the deformation characteristic of coarse grain soil material, be unfavorable for earthen structure（Artificial islands and reefs, high ferro roadbed, Gao Tushi Dam, nuclear power plant's sea work structures）Exact Design and safety evaluation.The measurement method of rubber-oil-pipe sensor mainly has at present：

Embedding cylindrical rod method：This method is the embedding copper rod with the contour different-diameter of sample of the heart in the sample, and assumes sample It is overall to become in a linear relationship with copper rod diameter, the volume change caused by rubber-oil-pipe sensor is estimated accordingly.But this method sample system It is standby relatively difficult, and copper rod can limit axial deformation, and cause the stress concentration of the soil body near copper rod, cause sample totally to become Hypothesis in a linear relationship is inaccurate with copper rod diameter.

Hollow cylinder sample method：This method is the mathematic interpolation rubber-oil-pipe sensor amount become according to different inner diameters sample induration With the variation relation of confining pressure.This method is only applicable to hollow cylinder sample, can not be applied to three axis sample of traditional cylinder.

Double sized samples methods：This method is become and rubber film surface according to the test body of two various sizes of cylindrical specimens Long-pending difference determines the embedded quantity of rubber membrane.This method is needed according to two various sizes of triaxial apparatus, for larger-size Coarse-grained soil, this method needs to research and develop ultra-large type triaxial apparatus, therefore is difficult to apply to coarse-grained soil rubber-oil-pipe sensor measuring study.

Special device method：This method is to obtain the pass of rubber-oil-pipe sensor amount and rubber membrane area by making special device System, but this method measure rubber-oil-pipe sensor stress state and boundary condition with the difference of triaxial test, can not be complete The embedded quantity of rubber membrane during reflection ordinary triaxial test.

Local train mensuration：In the case of specimen size is larger, balancing gate pit space is sufficient, and axial direction and diameter may be used Become to displacement sensor sample skeleton body, then becomes the rubber-oil-pipe sensor amount that calculates according to displacement hull, but in confining pressure variation Under the conditions of the deformation that occurs of rubber-oil-pipe sensor, the inhomogeneities of cylinder sample radial deformation and rubber membrane through-thickness, It can influence the measurement accuracy of cylindrical specimens radial deformation.

Isotropism presumptive method：Deformation isotropism seeks soil body skeleton during this method assumes that first Isopiestic Experiment Practical distortion, but the hypothesis differ larger with practical, the skeleton displacement hull change of sample in especially first isobaric loading procedure It is larger（Including plasticity and flexible deformation two parts, mainly the former）, error caused by the hypothesis can be amplified.

In conclusion there is also all with measurement method for the embedded analysis of sample rubber membrane in coarse-grained soil triaxial test at present More problems.

Invention content

The shortcomings that it is an object of the invention to overcome the prior art and method and deficiency provide a kind of measurement coarse grain soil large-scale The method of sample rubber-oil-pipe sensor amount in triaxial test, this method can slightly be enclosed by being added during routine consolidation test CYCLIC LOADING link is pressed to realize the measurement of rubber-oil-pipe sensor amount, operation difficulty is low, step is simple, and effectively eliminates sample The influence of body discreteness.

The scheme that the present invention uses is：A kind of side measuring sample rubber-oil-pipe sensor amount in coarse-grained soil Large-scale Triaxial Experiments Method includes the following steps：

（a）Using Large-scale Triaxial Experiments equipment, press《Earthwork test rule》（SL237-1999）Middle conventional methods prepare full The three axis sample of coarse-grained soil of sum；

（b）It presses《Earthwork test rule》Routine consolidation test is carried out to sample, consolidation stresses divide multi-stage loading to desired value, every Add small magnitude confining pressure CYCLIC LOADING link at level-one consolidation stresses, cycle confining pressure amplitude is 50 kPa, number 5, the period 6 Min eliminates the plasticity incremental deformation of sample with this CYCLIC LOADING process, to measure the recoverable volume of sample in the link Deform amplitude and axial deformation amplitude；According to said method until target confining pressure；

（c）Based on rubber-oil-pipe sensor be recoverable principle and sample recoverable deformation only include rubber-oil-pipe sensor deformation and The two-part feature of coarse grain soil skeleton flexible deformation is recycled according to sample caused by confining pressure amplitude is recycled at every level-one consolidation stresses Cubic deformation amplitude and cycle axial deformation amplitude, measure rubber-oil-pipe sensor increment caused by confining pressure variation；Wherein, coarse-grained soil bone For frame elasticity cubic deformation amplitude according to isotropism calculating is assumed, the axial plastic strain amplitude of the cycle equal to 3 times is multiplied by the body of sample Product, axial strain are equal to axial deformation divided by specimen height；Rubber-oil-pipe sensor increment is equal to sample cycle cubic deformation amplitude and subtracts Coarse grain soil skeleton elastomer product deformation amplitude is gone, and overall according to rubber-oil-pipe sensor incremental computations rubber-oil-pipe sensor at different confining pressures Accumulated amount.

The beneficial effects of the invention are as follows：The measurement method does not have to otherwise designed and develops measure setting for rubber-oil-pipe sensor amount It is standby, the embedded quantity of rubber membrane can be measured using conventional large-scale triaxial apparatus.The measurement method operating procedure is simple, and avoids sample Discreteness, can accurately measure the embedded quantity that rubber membrane changes with confining pressure, for correct triaxial test middle coarse grained soil volume become Shape provides reliable technological means, has pushed the research of coarse grain soil mechanics characteristic and constitutive model, has good promotional value.

Description of the drawings

Fig. 1 is coarse-grained soil experiment grading curve.

Fig. 2 is confining pressure loading procedure.

Fig. 3 is rubber-oil-pipe sensor increment and coarse-grained soil skeleton cubic deformation amplitude at confining pressures at different levels.

Specific implementation mode

Below in conjunction with example, elaborate to above-mentioned measurement method.

A method of sample rubber-oil-pipe sensor amount in coarse-grained soil Large-scale Triaxial Experiments is measured, is included the following steps：

（a）Using Large-scale Triaxial Experiments equipment, press《Earthwork test rule》（SL237-1999）Middle conventional methods prepare full The three axis sample of coarse-grained soil of sum.The sample preparation Con trolling index of coarse-grained soil is that porosity is 0.20, and gradation of coarse grained soil curve is shown in Fig. 1.

（b）It presses《Earthwork test rule》Routine consolidation test, consolidation stresses point multistage are carried out to sample（Including 50 kPa, 100 kPa, 150 kPa, 250 kPa, 350 kPa, 450 kPa, 550 kPa, 650 kPa, 750 kPa, 950 kPa）Load To 1000 kPa of desired value, small magnitude confining pressure CYCLIC LOADING link is added at every level-one consolidation stresses, for example, cycle confining pressure width Value is 50 kPa, number 5, period are 6 min, and the plasticity incremental deformation of sample is eliminated with this CYCLIC LOADING process, to Measure the recoverable cubic deformation amplitude of sample in the link and axial deformation amplitude.According to said method until target confining pressure.Confining pressure Loading procedure is shown in Fig. 2.

（c）It is that recoverable principle and sample recoverable deformation only become including rubber-oil-pipe sensor based on rubber-oil-pipe sensor Shape and the two-part feature of coarse grain soil skeleton flexible deformation, according to sample caused by cycle confining pressure amplitude at every level-one consolidation stresses Cycle cubic deformation amplitude within the 5th period and cycle axial deformation amplitude, rubber membrane is embedding caused by measuring confining pressure variation Enter increment.Wherein, for coarse grain soil skeleton elastomer product deformation amplitude according to isotropism calculating is assumed, the cycle equal to 3 times is axial Strain（Axial strain is equal to axial deformation divided by specimen height）Amplitude is multiplied by the volume of sample.Rubber-oil-pipe sensor increment is equal to examination Sample cycle cubic deformation amplitude subtracts coarse grain soil skeleton elastomer product deformation amplitude, and is increased according to rubber-oil-pipe sensor at different confining pressures Amount calculates rubber-oil-pipe sensor totality accumulated amount.This method middle coarse grained soil skeleton cubic deformation is recoverable（Elasticity）, account for sample The ratio for recycling cubic deformation amplitude is 11.2% ~ 19.2%（See Fig. 3）（Rubber-oil-pipe sensor amount increases with the increase of particle size Add, therefore numerical value of the ratio in the coarse-grained soil of larger particle can smaller）.Assume that the sample calculated is radial according to isotropism Distortion inaccuracy is 20%, 40%（Caused by Soil Anisotropic）, then the sample skeleton body change error calculated is 13.3%, 26.6%, Therefore the error of rubber-oil-pipe sensor is only 1.5% ~ 2.6%, 3.0% ~ 5.2%.Therefore this measurement method has very high precision.

Claims (1)

1. a kind of method measuring sample rubber-oil-pipe sensor amount in coarse-grained soil Large-scale Triaxial Experiments, feature include the following steps：

（a）Using Large-scale Triaxial Experiments equipment, saturation is prepared by conventional methods in earthwork test rule, SL237-1999 Three axis sample of coarse-grained soil；

（b）Routine consolidation test is carried out to sample by earthwork test rule, consolidation stresses divide multi-stage loading to desired value, each Add small magnitude confining pressure CYCLIC LOADING link at grade consolidation stresses, cycle confining pressure amplitude is 50 kPa, number 5, the period 6 Min eliminates the plasticity incremental deformation of sample with this CYCLIC LOADING process, to measure the recoverable volume of sample in the link Deform amplitude and axial deformation amplitude；According to said method until target confining pressure；

（c）Based on rubber-oil-pipe sensor be recoverable principle and sample recoverable deformation only include rubber-oil-pipe sensor deformation and The two-part feature of coarse grain soil skeleton flexible deformation is recycled according to sample caused by confining pressure amplitude is recycled at every level-one consolidation stresses Cubic deformation amplitude and cycle axial deformation amplitude, measure rubber-oil-pipe sensor increment caused by confining pressure variation；Wherein, coarse-grained soil bone For frame elasticity cubic deformation amplitude according to isotropism calculating is assumed, the axial plastic strain amplitude of the cycle equal to 3 times is multiplied by the body of sample Product, axial strain are equal to axial deformation divided by specimen height；Rubber-oil-pipe sensor increment is equal to sample cycle cubic deformation amplitude and subtracts Coarse grain soil skeleton elastomer product deformation amplitude is gone, and overall according to rubber-oil-pipe sensor incremental computations rubber-oil-pipe sensor at different confining pressures Accumulated amount.