CN114965944B - Coarse-grained soil expansion test device, system and method - Google Patents
Coarse-grained soil expansion test device, system and method Download PDFInfo
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Abstract
The invention discloses a coarse-grained soil expansion test device which comprises a fixing frame, a pressurizing lever, a water immersion tank, a dial indicator, an expansion assembly and a displacement transmission assembly, wherein the fixing frame is arranged on the pressing lever; the ratio of the side area of the sample to the bearing area of the sample is 0.97-1.46. The invention also provides a coarse-grained soil expansion test system, which comprises a computer system and the coarse-grained soil expansion test device. The invention also provides a coarse-grained soil expansion test method which is realized by the coarse-grained soil expansion test device. By adopting the technical scheme, the coarse-grained soil expansion test device, the coarse-grained soil expansion test system and the coarse-grained soil expansion test method can obtain more accurate expansion rate values by setting the ratio of the side area of the sample to the bearing area of the sample within the range of 0.97-1.46.
Description
Technical Field
The invention relates to a coarse-grained soil expansion test device, system and method, and belongs to the technical field of filling soil expansion test.
Background
The expansive clay is high-plasticity clay, has higher general bearing capacity, has the characteristics of water absorption expansion, water loss shrinkage, repeated expansion and contraction deformation, water immersion bearing capacity attenuation, dry shrinkage crack development and the like, and has extremely unstable properties, so that uneven vertical or horizontal expansion and contraction deformation of a building is often generated, and displacement, cracking, tilting and even damage are caused. Coarse-grained soil refers to soil with a mass of the coarse grain group (grain size >0.075 mm) of more than 50% of the total mass. Coarse-grained soil is generally formed on the surface of mountain bodies, is formed by loosely stacking and mixing rock on the surface of mountain bodies after the mountain bodies are stripped by virtue of weathering, is often called as "mountain skin soil" when used as roadbed filler, has complex rock-mineral components and complex proportion of various minerals, and can certainly cause different degrees of expansion damage to roadbed when used as roadbed filler if the coarse-grained soil contains expansion rock soil.
In the existing geotechnical specifications, such as 'geotechnical test regulations for railway engineering' TB10102-2010 and 'geotechnical test method Standard' GB/T50123-2019, no test method for expanding coarse-grained soil exists, and only fine-grained soil exists. The expansion test items are as follows: free expansion rate test, expansion force test, expansion rate test, cation and montmorillonite content test according to the test of TB10103-2008 of the chemical analysis of railway engineering and rock and soil. Wherein the free expansion rate test is applicable to soil with a particle size of <0.5 mm; taking soil with the particle size less than 0.25mm according to a cation and montmorillonite content test; the swelling force test and the swelling rate test are applicable to undisturbed soil and fine disturbance soil compaction samples, and are all carried out on fine soil. In doing the coarse-grained soil expansion test, only fine grains <0.5mm and <0.25mm are screened from fine-grained soil for free expansion rate test, cation and montmorillonite content test, and as a result, the fine grains tend to be made to be strongly expandable, while in fact most of the coarse grains are not expanded rock, and it is theoretically impossible to generate such large expansion. Therefore, this result cannot accurately reflect the overall expansibility index of the coarse-grained soil. Only by doing the expansion rate and expansion force test of the whole coarse-grained soil, the expansion index of the whole coarse-grained soil can be directly and accurately reflected. Furthermore, the chinese patent document CN210427563U of the prior application discloses a coarse filler expansion tester which attempts to obtain the expansion force of coarse filler by measuring the expansion rate of coarse filler under different pressures, but the accuracy of the test results is found to be not high during the test.
Disclosure of Invention
Therefore, the invention aims to provide a coarse-grained soil expansion test device, system and method with relatively accurate expansion rate test results.
In order to achieve the aim, the coarse-grained soil expansion test device comprises a fixing frame, a pressurizing lever, a water soaking tank, a dial indicator, an expansion assembly and a displacement transmission assembly; the fixing frame comprises a test platform and a plurality of supporting arms which are connected with the test platform and used for supporting the test platform; the immersion tank is placed on the test platform, and the expansion assembly is placed in the immersion tank; the displacement transmission assembly comprises two straight rods, the upper ends of the two straight rods are connected with the pressurizing frame, the lower ends of the two straight rods penetrate through the testing platform and are connected with a lever pressurizing seat, the lever pressurizing seat is rotationally connected with a pressurizing lever, and the two ends of the pressurizing lever are provided with balancing blocks and pressurizing weights; the pressing frame is provided with a linkage rod which penetrates through the pressing frame and the lower end of which is in contact with the expansion assembly, and the upper end of the linkage rod can be in contact with the dial indicator; the expansion assembly comprises a test die, a pressurizing upper cover and a test die bottom plate, and water permeable holes are respectively formed in the pressurizing upper cover and the test die bottom plate; the pressurizing upper cover and the test die bottom plate clamp the sample therein; the grain diameter of the largest particles of the soil sample sampled by the sample is smaller than or equal to 40mm; the ratio of the side area of the sample to the bearing area of the sample is 0.97-1.46.
The diameter of the sample is 247mm, and the height of the sample is 60 mm-90 mm.
The ratio of the side area of the sample to the bearing area of the sample was 1.46.
The diameter of the sample was 247mm and the height was 90mm.
Lubricating oil is also coated on the inner side wall of the test die.
The invention also provides a coarse-grained soil expansion test system, which comprises a computer system and the coarse-grained soil expansion test device as claimed in any one of claims 1 to 5, wherein a gravity sensor is arranged on the coarse-grained soil expansion test device and is used for detecting the load weight of a pressurizing weight on a pressurizing lever, a dial indicator on the coarse-grained soil expansion test device and the gravity sensor are connected to the computer system, and the computer system is used for recording the reading of the dial indicator, the load weight of the pressurizing weight and calculating the expansion rate.
The invention also provides a coarse-grained soil expansion test method, which comprises the following steps:
placing the coarse-grained soil into a test mold and forming by a press machine to form a sample in the coarse-grained soil expansion test device according to any one of claims 1-4;
a test mold having a sample therein is placed in a soaking tank of the coarse soil expansion test device according to claim 1, and an expansion ratio test is performed.
Before coarse soil is filled into the test mold, the inner side wall of the test mold is coated with lubricating oil.
After the press machine performs sample molding, pushing the sample, and enabling the sample to move for 5 mm-10 mm in the test die.
The expansion rate test comprises the following steps:
(1) Applying a pre-pressure of 1kPa to ensure that all parts of the coarse-grained soil expansion test device are in good contact; the pointer of the dial indicator is adjusted to the middle position of the full range, the precompression is removed, and the initial reading R is recorded 0 ；
(2) The pressure is applied in a grading way according to the preset requirement, the interval time of each stage of pressure is 10min, and the deformation per hour after the last stage of pressure is applied is smaller than 0.01mm, so that the pressure is regarded as stable reading after the pressure is applied;
(3) After the pressure is applied, water is injected between the inner wall of the soaking tank and the outer wall of the test mold after the stable reading appears, so that water enters the test sample from bottom to top, and the water surface is kept to be higher than the top surface of the test sample by about 20mm;
(4) And measuring and recording readings of the dial indicator every 4 hours after soaking until the difference between the readings is not more than 0.005mm, taking the readings as stable readings after soaking and expanding the sample, and recording the sampleStabilize reading R after swelling in water pc ；
(5) Take out the sample and weigh the wet sample weight m 0 Drying and cooling, and weighing the dry sample d Calculating the water content w after expansion;
(6) The foregoing procedure was repeated to determine test data at 5 different pressures, where the minimum pressure was 0kPa and the maximum pressure applied to ensure that the expansion rate was negative.
The test shows that the ratio of the side area of the sample to the bearing area of the sample has the greatest influence on the expansion rate, and by adopting the technical scheme, the coarse-grained soil expansion test device, the system and the method provided by the invention, the ratio of the side area of the sample to the bearing area of the sample is set in the range of 0.97-1.46, so that a more accurate expansion rate value can be obtained.
Drawings
FIG. 1 is a schematic front view of the coarse soil expansion test device of the present invention.
FIG. 2 is a perspective view of the coarse soil expansion test apparatus according to the present invention.
FIG. 3 is a schematic illustration of a sample and a test pattern placed in a dip tank.
FIG. 4 is a graph of time versus expansion for a set of data obtained from an expansion rate test.
FIG. 5 is a plot of side area/area versus expansion ratio for a set of data obtained from an expansion ratio test.
FIG. 6 is a photograph of a sample of particles selected for the swell ratio test having a maximum particle size of less than 40mm.
FIG. 7 is a graph of expansion versus pressure.
Fig. 8 is a graph of load-weight relationship.
Fig. 9 is a graph showing the relationship between deformation and load.
FIG. 10 is a graph of sample height versus expansion ratio for a set of data obtained from an expansion ratio test.
FIG. 11 is a graph showing the relationship between the sample diameter and the expansion ratio of a set of data obtained by the expansion ratio test.
FIG. 12 is a photograph showing a sample having a maximum particle diameter of 20mm for a sample selected for the expansion ratio test.
FIG. 13 is a graph of sample height versus expansion ratio for a set of data obtained from an expansion ratio test.
FIG. 14 is a photograph showing a sample having a maximum particle diameter of 5mm for a sample selected for the expansion ratio test.
FIG. 15 is a graph of sample height versus expansion ratio for a set of data obtained from an expansion ratio test.
Description of the embodiments
The invention is described in further detail below with reference to the drawings and the detailed description.
As shown in figures 1-3, the coarse-grained soil expansion test device comprises a fixed frame, a pressurizing lever 1, a soaking tank 2, a dial indicator 3, an expansion assembly and a displacement transmission assembly; the fixing frame comprises a test platform 4 and a plurality of supporting arms 5 connected with the test platform 4 and used for supporting the test platform 4; the immersion tank 2 is placed on the test platform 4, and the expansion assembly is placed in the immersion tank 2; the displacement transmission assembly comprises two straight rods 6, the upper ends of the two straight rods 6 are connected with a pressurizing frame 7, the lower ends of the two straight rods 6 penetrate through the testing platform 4 and are connected with a lever pressurizing seat 8, the lever pressurizing seat 8 is rotationally connected with the pressurizing lever 1, and balance weights 9 and pressurizing weights 10 are arranged at two ends of the pressurizing lever 1; the lower end face of the test platform 4 is provided with a mounting seat 17, and the pressurizing lever 1 is mounted on the mounting seat 17. The pressing frame 7 is provided with a linkage rod 11 which passes through the pressing frame 7 and the lower end of which is contacted with the expansion assembly, and the upper end of the linkage rod 11 can be contacted with the dial indicator 3; the expansion assembly comprises a test die 12, a pressurizing upper cover 13 and a test die bottom plate 15, wherein water permeable holes 14 are respectively formed in the pressurizing upper cover 13 and the test die bottom plate 15, and a sample 16 is placed in the test die 12 and clamped by the pressurizing upper cover 13 and the test die bottom plate 15.
The pressurizing weight 10 is placed on a double-row load bracket, the double-row load bracket comprises a top rod 18 and a bottom rod 19, two vertical rods 20 are arranged between the top rod 18 and the bottom rod 19, and the pressurizing weight 10 can be placed on the bottom rod 19 in a manner of being stacked in two rows, so that the overall height of the pressurizing weight 10 is reduced, and the up-and-down floating amount of the pressurizing lever 1 is increased.
Three different samples having diameters of 24.72cm, 15.14cm and 10.70cm were subjected to comparative tests by the above-mentioned test apparatus.
As shown in FIG. 6, the sample was a fine granular soil having an expansive property and a maximum grain size of 5mm and crushed stone having a maximum grain size of 40mm, and the sample was prepared by mixing 1:1 ratio, and the maximum dry density of 1.88g/cm 3 The soil sample was air-dried and then tested, and the air-dried water content was 3.3%.
According to the height and diameter of the sample, the volume of the sample is calculated, and according to the maximum dry density and the optimal water content, the weight of the soil sample required by each sample is calculated.
The inside of the test mold 12 is coated with lubricating oil, and a weighed soil sample is pressed into the test mold 12 by a press machine to form the sample (filter paper is put on the upper and lower surfaces of the sample in the test mold 12 before pressing, and 3 seams are cut in the middle of the filter paper to facilitate water permeation). In other test runs, it may be desirable to move the test specimen up 5-10mm in the test mold 12 after the test specimen is formed to reduce stress between the inner wall of the test mold 12 and the outer wall of the test specimen.
The prepared sample is put into a soaking tank 2 of a test device, a pressurizing cover plate is put on the soaking tank, a dial indicator 3 is installed, and a precompression of 1kPa is applied, so that all parts of the instrument are in good contact. The pointer of the dial indicator 3 is adjusted to be about the median of the full range, the precompression is removed, and the initial reading R is recorded 0 。
The pressure is applied according to the preset requirement, when the pressure is large, the pressure should be applied in a grading way, the interval time of each stage of pressure is 10min, the impact should be avoided during the pressure application, and the deformation per hour after the last stage of pressure application is less than 0.01mm, so that the stable reading after the pressure application can be considered.
Pure water is injected between the inner wall of the soaking tank 2 and the outer wall of the test mold 12, so that the water enters the test sample from bottom to top, and the water surface is kept to be higher than the top surface of the test sample by about 20mm.
The reading of the dial indicator 3 is measured and recorded every 4 hours after soaking until the difference value of the two readings is not more than 0.005mm, the last reading is regarded as the stable reading after the sample swells after soaking, and the stable reading R is recorded pc . If neededThe relationship between swelling and time was determined and the reading of the dial 3 was recorded every 10min for the first 2 hours after immersion.
After the test is completed, the water in the water immersion tank 2 and the top surface of the sample is discharged, the load is removed, the sample is taken out, and the wet sample weight m is weighed 0 Drying and cooling, and weighing the dry sample d The water content w after expansion was calculated.
Test data at 5 different pressures should generally be measured. Wherein the minimum pressure should be 0kPa and the maximum pressure should ensure that the expansion ratio is negative after application.
The invention also provides a coarse-grained soil expansion test system, which comprises a computer system and the coarse-grained soil expansion test device, wherein the coarse-grained soil expansion test device is provided with a gravity sensor, the gravity sensor is used for detecting the weight of the pressurizing weight 10 on the pressurizing lever 1, the dial indicator 3 on the coarse-grained soil expansion test device and the gravity sensor are connected to the computer system, and the computer system is used for recording the reading of the dial indicator 3, the weight of the pressurizing weight 10 and calculating the expansion rate.
The expansion rate at each stage of pressure is calculated as follows:
wherein:
V HPC -expansion (%) at each stage pressure, calculated to 0.1%;
R pc -stable reading (mm) after immersion expansion of the sample at each stage of pressure;
R y -the instrument compression deformation (mm) at each stage of pressure;
R 0 -initial reading (mm) of dial indicator 3 at the start of the test;
H 0 -the original height (mm) of the sample.
The water absorption rate under each level of pressure is calculated as follows:
wherein:
W cx -water absorption (%) at each stage pressure, calculated to 0.1%;
m 0 -wet soil weight (g) after soaking and swelling of the sample under each stage of pressure;
m d -weight of dry soil (g) after soaking and swelling of the sample under each stage of pressure;
W o original moisture content (%) of sample.
On rectangular paper, the expansion rate under each level of pressure is taken as an ordinate, the pressure is taken as an abscissa, a curve of the relation between the expansion rate and the pressure is drawn, the expansion rate corresponding to the curve at 0kPa is the non-load expansion rate of the sample, and the pressure at the intersection point of the curve and the abscissa is the expansion force P of the sample p As shown in fig. 7.
Under the load action, the test device generates instrument deformation due to deformation of each part, compaction of gaps among the parts and the like, and the deformation correction of the dilatometer is carried out because the proportion of the compression deformation of the sample instrument with small expansion to the deformation of the soil sample is large, so that large errors can be brought to expansion indexes.
The test device should be calibrated once a year during use. For example, during this time, the replacement of the instrument parts and the pressure transmitting plate, the pressurizing frame 7, the immersion tank 2, etc., or the influence of moving, vibration, etc. should be corrected at any time.
Inspection and adjustment of the test device:
(1) The lever pressing seat 8 must be stable, the table top of the pressed test platform 4 must be horizontal, the vertical rod of the pressing frame 7 must be vertical, and the pressing frame must not contact with the side edge of the table top, otherwise, the table top should be trimmed.
(2) The horizontal rule is used for checking whether the cross beam of the pressurizing frame 7 is horizontal or not, if the cross beam is inclined, screws on the cross beam are used for adjusting the cross beam to the horizontal position, the distance between the convex head of the cross beam and the pressurized table top is just suitable for the height after the pattern is assembled, and the concave part of the pressurizing upper cover 13 can be tightly adhered with the convex head of the cross beam.
(3) Correction of lever ratio: the dynamometer is placed under the convex head of the cross beam, the dynamometer is placed stably, weights with standard weight are applied step by step every 10min, the corresponding load when the weights of each level are applied is recorded, the weight of the weights is taken as the abscissa, the load is taken as the ordinate, and a correction curve is drawn, as shown in figure 8. The slope of the curve is the leverage ratio.
Correcting the deformation of the dilatometer:
(1) The test device was filled with a metal block instead of the sample, and a dial gauge 3 was installed.
(2) Weights with standard weight are applied step by step, the weights are loaded every 10min, and the corresponding reading of the dial indicator 3 under each load is measured and recorded.
(3) And after the reading of the dial indicator 3 under the maximum primary load is recorded, unloading is carried out every 10min according to the order opposite to the loading grade, and the corresponding reading of the dial indicator 3 is recorded until the pressure is completely unloaded.
(4) The test device was removed and reinstalled. Repeating the above steps and measuring. The average value is taken as the deformation under the load of each stage, and the parallel difference value is required to be not more than 0.08mm.
(5) The correction curve is drawn with the deformation amount of the dilatometer as the ordinate and the load as the abscissa, as shown in fig. 9.
In the test process of the prior art, the accuracy of the test result is not high, and the test shows that the ratio of the side area of the sample to the bearing area of the sample is the largest influence on the expansion rate, and in addition, whether the inner wall of the test die 12 has larger friction resistance with the sample and whether the inner wall of the test die 12 has stress with the sample have influence on the test result.
The above effect was determined by the following test steps:
(1) The influence of lubricating oil on the expansion ratio by lubricating oil and non-lubricating oil on the comparative mold 12. The same test piece size is kept by using the same test piece 12, the inner wall of one test piece 12 is coated with engine oil, and the inner wall of the other test piece 12 is not coated with engine oil for comparison.
(2) The influence of different sample heights on the expansion rate under the same pressure and sample diameter is compared. Samples of various heights, such as 4, 6, 8, 9, 10, 13, and 17cm, were prepared and compared with the same size test mold 12.
(3) The effect of different diameters on the expansion rate was compared under the conditions of the same height of the test sample. Test molds 1224.72cm, 15.14cm and 10.70cm with different diameters are selected for comparison under the same pressure and test piece height.
(4) When a press machine is used to prepare the sample, the influence on the expansion rate is compared with whether the sample is pushed up after molding. The same sample is used for testing the 12 pieces, the sizes of the test pieces are kept the same, one sample is directly pressed into the test piece for molding, the other sample is pushed in the test piece 12 after being pressed into the test piece for molding, and then the test pieces are respectively put into a test device for test comparison.
(5) The effect of the stainless steel test pattern 12 on the expansion rate was compared with that of the steel test pattern 12 which is liable to rust. The comparison was made with a stainless steel test 12 of the same test piece size and a stainless steel test 12 piece.
Comparing the experimental results:
(1) The influence of oil and no oil on the expansion rate of the test mold 12 was compared.
Table 1: expansion ratio comparison of test mold 12 oiled and not oiled
As can be seen from the comparison experiment, the expansion rate of the inner wall of the test mold 12 is larger than that of the inner wall without brushing.
(2) The influence of different sample heights on the expansion rate under the same pressure and sample diameter is compared.
Table 2: expansion ratio comparison of different heights of test sample
As shown in fig. 10, the experimental data shows that the expansion rate decreases with increasing specimen height at the same pressure and diameter. When the height is greater than 90mm, the expansion rate values of the 3 diameter samples are obviously smaller; the expansion rate data has larger discreteness when the height is smaller than 60 mm; at a height of 60-90mm, the expansion rate value of the test piece with the diameter of 247mm is relatively larger than that of the test piece with the diameter of 151mm and 107mm, and the test pieces are similar, wherein the expansion rate data with the height of 90mm is minimum in discreteness and maximum in average value.
(3) The influence of different sample diameters on the expansion rate under the same pressure and the same sample height is compared.
Table 3: expansion ratio comparison of different diameters of 60mm high samples
As shown in fig. 11, the experimental data shows that the expansion ratio is significantly reduced with the decrease of the sample diameter at the same pressure and sample height. As can be seen, the expansion ratio data generated by the 3 diameter test pieces when the heights are the same, and the expansion ratio value of 247mm in diameter is relatively significantly larger.
(4) And comparing whether the test sample is jacked after being molded, and the influence on the expansion rate is reduced.
Table 4: comparison of the expansion Rate of the Pushing of the test sample after its formation
Experiments show that the stress between the side wall of the test die 12 and the test sample has great influence on the expansion rate, the pressure of the press machine is about 100kN when the workpiece is manufactured, and if a soaking experiment is directly carried out, the stress exists between the outer side surface of the test sample and the inner wall of the test die 12, so that the test sample needs to be pushed to move for 5 mm-10 mm in the test die 12 after the test sample is pressed and molded, and the stress is eliminated. As can be seen from the comparison data, the expansion rate increases after jacking the test specimen.
(5) The effect of the stainless steel test 12 on the expansion rate was compared with the stainless steel test 12.
Table 5: test die 12 contrast
As can be seen from Table 5, the expansion ratio measured using the stainless steel test die 12 is significantly higher than that of the easily rusted steel test die 12. Since the test is performed in water, the use of stainless steel for the test die 12 is certainly the correct choice.
(6) Expansion ratio versus time.
As shown in FIG. 4, the expansion and growth of coarse-grained soil are obvious in the first 2 hours after soaking, the growth is slowed down in 2-24 hours, and the growth gradually becomes stable after 48 hours. According to the stability standard of the standard consolidation test, namely that the deformation of the 1h sample is not more than 0.005mm, the sample can reach stability after 24h, and in fact, a small amount of expansion can be generated between 24h and 48 h. Therefore, the expansion stability criteria for coarse-grained soil are set as: after 48 hours of immersion, the deformation of the 4-hour sample is not more than 0.005mm, which is suitable.
(7) Influence of test piece side area on expansion rate.
Table 6: influence of side area/area (ratio) on expansion ratio
As shown in fig. 5, it is understood from the experimental results that the larger the side area/area ratio is, the smaller the expansion ratio is. When the side area/area is larger than 1.5 as a whole, the expansion ratio numerical group is in a low position; the expansion rate numerical group is at a higher position when the side area/area is 0.9-1.5; when the side area/area is smaller than 0.9, the expansion ratio value is in a state of high or low differentiation, and the dispersion is large. Thus, the side area/area of the sample is preferably 0.9-1.5. The height should be considered to be more than 1.5 times the maximum particle size of the sample (if the height of the sample is too small, less than or near the maximum particle size of the sample, the sample will be crushed and will not conform to the actual state after the filler is applied), such as: the diameter of the test piece is 247mm, and the height is 60 mm-90 mm.
Results statistical analysis:
table 7: results analysis table of maximum particle size 40mm
According to statistical experimental data, the expansion rate generated by the test die with the diameter of 247mm is obviously larger, the average result is more stable at 60, 80 and 90mm, and the expansion rate generated by the test die with the diameters of 151 and 107mm is obviously smaller. Considering the influence of the maximum particle diameter and the representativeness of the sample, it is preferable to take the sample size of 247mm and 90mm in diameter for the soil sample with the maximum particle diameter of 40mm.
As shown in fig. 12, a soil sample was selected as fine granular soil having an expansive property and a maximum grain size of 5mm and crushed stone having a maximum grain size of 20mm, and the ratio of 1:1 ratio, and then performing experiments. The maximum dry density was found to be 1.84g/cm 3 After the soil sample was air-dried, an experiment was performed, and the air-dried water content was 3.5%.
Table 8: maximum particle size 20mm results analysis table
As shown in FIG. 13, the experimental comparison chart and the statistical data show that the expansion rate generated by the sample with the diameter of 247mm is obviously larger, and the average result of the sample with the heights of 20mm, 40mm and 60mm is more stable; the height of the sample with the diameter of 151mm is 20mm, and the expansion rate of 40mm is relatively close to the large value with the diameter of 247 mm; the sample with diameter of 107mm has a smaller expansion rate and significantly decreases with increasing height. Taking the influence of the maximum grain size and the representativeness of the sample (taking out soil as much as possible) into consideration for the soil sample with the maximum grain size of 20mm, and taking the size of the sample to be 247mm in diameter and 60mm in height; in view of the convenience of operation of the test, the test piece size can also be 151mm in diameter and 40mm in height.
As shown in FIG. 14, an experiment was performed by selecting a soil sample as fine granular soil having an expansive property and a maximum grain diameter of 5 mm. The maximum dry density was found to be 1.80g/cm 3 After the soil sample was air-dried, an experiment was performed, and the air-dried water content was 6.1%.
Table 9: maximum particle size 5mm results analysis table
As shown in FIG. 15, the soil sample having a maximum grain size of 5mm was subjected to comparison of 3 different specimen diameters (247 mm, 151mm, 107 mm) and 4 different heights (10 mm, 20mm, 30mm, 40 mm). The experimental comparison and statistics data show that the experimental results of the test-mould test pieces with the diameter of 247mm are more stable and larger at the heights of 20mm, 30mm and 40mm; the height of a test piece with the diameter of 151mm is 10mm and 20mm, and the experimental result is relatively stable and relatively large; the test piece with the diameter of 107mm has the stable and large experimental results at the heights of 10mm and 20mm. For a soil sample with a maximum grain size of 5mm, taking the influence of the maximum grain size and the representativeness of the sample (taking as much soil as possible) into consideration, the sample size is preferably 247mm in diameter and 40mm in height.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
1. The utility model provides a coarse granule soil expansion test device which characterized in that: comprises a fixing frame, a pressurizing lever, a water soaking tank, a dial indicator, an expansion assembly and a displacement transmission assembly; the fixing frame comprises a test platform and a plurality of supporting arms which are connected with the test platform and used for supporting the test platform; the immersion tank is placed on the test platform, and the expansion assembly is placed in the immersion tank; the displacement transmission assembly comprises two straight rods, the upper ends of the two straight rods are connected with the pressurizing frame, the lower ends of the two straight rods penetrate through the testing platform and are connected with a lever pressurizing seat, the lever pressurizing seat is rotationally connected with a pressurizing lever, and the two ends of the pressurizing lever are provided with balancing blocks and pressurizing weights; the pressing frame is provided with a linkage rod which penetrates through the pressing frame and the lower end of which is in contact with the expansion assembly, and the upper end of the linkage rod can be in contact with the dial indicator; the expansion assembly comprises a test die, a pressurizing upper cover and a test die bottom plate, and water permeable holes are respectively formed in the pressurizing upper cover and the test die bottom plate; the pressurizing upper cover and the test die bottom plate clamp the sample therein; the grain diameter of the largest particles of the soil sample sampled by the sample is smaller than or equal to 40mm; the ratio of the side area of the sample to the bearing area of the sample is 0.97-1.46.
2. The coarse-grained soil expansion test device of claim 1, wherein: the diameter of the sample is 247mm, and the height of the sample is 60 mm-90 mm.
3. The coarse-grained soil expansion test device of claim 1, wherein: the ratio of the side area of the sample to the bearing area of the sample was 1.46.
4. The coarse-grained soil expansion test device of claim 1, wherein: the diameter of the sample was 247mm and the height was 90mm.
5. A coarse soil expansion test device according to any one of claims 1 to 4, wherein: lubricating oil is also coated on the inner side wall of the test die.
6. The utility model provides a coarse granule soil expansion test system which characterized in that: the device comprises a computer system and the coarse-grained soil expansion test device as set forth in any one of claims 1-5, wherein a gravity sensor is arranged on the coarse-grained soil expansion test device and used for detecting the load weight of a pressurizing weight on a pressurizing lever, a dial indicator on the coarse-grained soil expansion test device and the gravity sensor are connected to the computer system, and the computer system is used for recording the reading of the dial indicator, the load weight of the pressurizing weight and calculating the expansion rate.
7. The coarse-grained soil expansion test method is characterized by comprising the following steps of:
placing the coarse-grained soil into a test mold and forming by a press machine to form a sample in the coarse-grained soil expansion test device according to any one of claims 1-4;
a test mold having a sample therein is placed in a soaking tank of the coarse soil expansion test device according to claim 1, and an expansion ratio test is performed.
8. The coarse-grained soil expansion test method according to claim 7, wherein: before coarse soil is filled into the test mold, the inner side wall of the test mold is coated with lubricating oil.
9. The coarse-grained soil expansion test method according to claim 7, wherein: after the press machine performs sample molding, pushing the sample, and enabling the sample to move for 5 mm-10 mm in the test die.
10. A coarse soil expansion test method according to any one of claims 7 to 9, wherein the expansion rate test comprises the steps of:
(1) Applying a pre-pressure of 1kPa to ensure that all parts of the coarse-grained soil expansion test device are in good contact; the pointer of the dial indicator is adjusted to the middle position of the full range, the precompression is removed, and the initial reading R is recorded 0 ；
(2) The pressure is applied in a grading way according to the preset requirement, the interval time of each stage of pressure is 10min, and the deformation per hour after the last stage of pressure is applied is smaller than 0.01mm, so that the pressure is regarded as stable reading after the pressure is applied;
(3) After the pressure is applied, water is injected between the inner wall of the soaking tank and the outer wall of the test mold after the stable reading appears, so that water enters the test sample from bottom to top, and the water surface is kept to be higher than the top surface of the test sample by about 20mm;
(4) And measuring and recording readings of the dial indicator every 4 hours after soaking until the difference between the readings is not more than 0.005mm, regarding the readings as stable readings after soaking and expanding the sample, and recording the stable readings R after soaking and expanding the sample pc ；
(5) Take out the sample and weigh the wet sample weight m 0 Drying and cooling, and weighing the dry sample d Calculating the water content w after expansion;
(6) The foregoing procedure was repeated to determine test data at 5 different pressures, where the minimum pressure was 0kPa and the maximum pressure applied to ensure that the expansion rate was negative.
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