CN107860685B - Method for detecting water content of sandy soil - Google Patents
Method for detecting water content of sandy soil Download PDFInfo
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Abstract
The invention disclosesA method for detecting the water content of sandy soil comprises the following steps: step 1: taking a sandy soil sample, adding water according to a certain proportion to prepare a water-containing soil samplea(ii) a Step 2: the weight of the measuring flask is measured asm 0 Soil sampleaPlacing in a volumetric flask; and step 3: adding water into the volumetric flask until the water content is lower than the scale mark A, and adding water until the water content reaches the scale mark A after bubbles are eliminated; weighing the mass at the momentm 10 (ii) a And 4, step 4: cleaning and drying the volumetric flask, adding water to the volumetric flask to a scale A to obtain the mass of the volumetric flask plus the waterm 20 (ii) a And 5: taking soil sample with fixed massaDrying to obtain water contentω 0 (ii) a Step 6: calculating the calculated specific gravityG sc : and 7: will calculate the specific gravityG sc Replacing the actual specific gravity of sandy soil in the specific gravity methodG s Detecting the water content in the sandy soil according to a specific gravity method; the invention has high applicability, high detection precision and high detection speed.
Description
Technical Field
The invention relates to a method for detecting the water content of sandy soil.
Background
Sandy soil is used as an important building material and has wide application in the fields of hydraulic engineering, house construction, highway engineering and the like, such as filling materials of earth-rock dams, fine aggregate of concrete, filling materials of roadbeds and the like; in the filling process of the earth-rock dam and the roadbed, the water content of sandy soil has great influence on the compaction effect; the water content is too small, the roller cannot be quickly rolled and compacted, and the compacting effect is influenced by too large water content; in the process of mixing concrete, if the moisture content detection of sand and stone is not accurate, the inaccurate weighing of sand, stone and water is directly caused, and the mixing of concrete by completely adopting dry sand and stone is unrealistic, in particular to a large-volume hydraulic concrete structure; therefore, the method for detecting the water content of the sandy soil is very important.
The existing off-line detection method for the water content of sandy soil comprises a drying method, an alcohol combustion method and a specific gravity method, and the on-line detection method comprises a microwave method, an electric oven method, a resistance method, a capacitance method, an infrared method and the like; although the online detection method has high detection speed, the detection result has large error and can not be applied to actual engineering; the drying method is more accurate, and the detection results of other methods are generally compared with the drying method; however, according to the requirements of geotechnical test regulations (SL237-1999), the drying time of sandy soil is not less than 6h, and the requirement of rapid detection in actual engineering cannot be met; in addition, the oven power used by the drying method is generally between 1kW and 6kW, and more electric energy needs to be consumed once detection is carried out.
Therefore, the water content of sandy soil is detected to have poor accuracy of an online detection result and cannot meet the requirement; the drying method has the defects of long time consumption, high electric energy consumption and the like; the hydrometer method has large detection error and large formula sensitivity, and cannot meet the practical engineering application.
Disclosure of Invention
The invention discloses a method for detecting the water content of sandy soil, which has high applicability, high detection precision and high detection speed.
The technical scheme adopted by the invention is as follows: a method for detecting the water content of sandy soil comprises the following steps:
step 1: taking a sandy soil sample, adding water according to a certain proportion to prepare a water-containing soil sample a;
step 2: taking a volumetric flask, weighing the mass m0Placing the soil sample a in a volumetric flask;
and step 3: adding water into the volumetric flask until the water content is lower than the scale mark A, and adding water until the water content reaches the scale mark A after bubbles are eliminated; weighing the mass m at this moment10；
And 4, step 4: cleaning and drying the volumetric flask, adding water to the volumetric flask to a scale A to obtain the mass m of the volumetric flask plus the water20；
And 5: taking a soil sample a with certain mass, and obtaining the water content omega of the soil sample a by a drying method0；
Step 6: specific gravity G was calculated by the following formulasc：
And 7: will calculate specific gravity GscReplacing the actual specific gravity G of sandy soil in the specific gravity methodsAnd detecting the water content in the sandy soil according to a specific gravity method.
Further, the temperature is kept consistent during the operation of the step 3 and the step 4.
Further, measuring the temperature of the mixed solution in the step 3 to be T; the step 4 also comprises the following processes: taking n temperature values near the temperature T, respectively adding water with the temperature corresponding to the n temperature values into the same volumetric flask to the scale mark A, and respectively weighing the mass of the water; drawing a curve of the mass changing along with the temperature according to the mass obtained at different temperatures; searching the mass m corresponding to the temperature at the moment according to the curve20。
Further, the hydrous soil sample a is prepared according to 5 different proportions in the step 11、a2、a3、a4、a5Repeating the steps 2-6 to respectively calculate the calculated specific gravity Gsc1、Gsc2、Gsc3、Gsc4And Gsc5Then, the arithmetic mean of the calculated specific gravities is taken as the calculated specific gravity Gsc。
Further, a hydrous soil sample1、a2、a3、a4、a5Taking two portions of each hydrous soil sample, calculating the calculated specific gravity of each hydrous soil sample according to the steps 2-6 respectively, and taking the arithmetic average of the 10 calculated specific gravities to obtain the calculated specific gravity Gsc。
Further, in the step 7, a volumetric flask which is the same as the volumetric flask used in the steps 1-7 is adopted, and the quality of the sampling product is the same as that in the step 2; measuring the temperature T of the mixed liquid formed by the sand soil sample, the volumetric flask and the water1(ii) a According to temperature T1Searching corresponding mass m from curve of mass changing along with temperature20。
Furthermore, an electronic balance with the measuring range of 2000-4000 g and the division value of 0.01g is adopted in the process of weighing the mass.
The invention has the beneficial effects that:
(1) the invention calculates the specific gravity GscInstead of G in the calculation by the hydrometer methodsThe error of the detection result of the water content is small, and the accuracy of the drying method is close to or achieved;
(2) compared with a drying method, the method of the invention can greatly shorten the detection time, has high precision and basically achieves the aim of real-time detection.
Detailed Description
The present invention is further illustrated by the following specific examples.
A method for detecting the water content of sandy soil comprises the following steps:
step 1: taking a sandy soil sample, adding water according to a certain proportion to prepare a water-containing soil sample a;
step 2: taking a volumetric flask, weighing the mass m0Placing the soil sample a in a volumetric flask;
and step 3: adding water into the volumetric flask until the water content is lower than the scale mark A, and adding water until the water content reaches the scale mark A after bubbles are eliminated; weighing the mass m at this moment10；
And 4, step 4: cleaning and drying the volumetric flask, adding water to the volumetric flask to a scale A to obtain the mass m of the volumetric flask plus the water20；
And 5: taking a soil sample a with certain mass, and obtaining the soil sample a by a drying methodWater content omega0；
Step 6: specific gravity G was calculated by the following formulasc：
And 7: will calculate specific gravity GscReplacing the actual specific gravity G of sandy soil in the specific gravity methodsAnd detecting the water content in the sandy soil according to a specific gravity method.
In the specific test process, in the step 7, in the process of detecting the water content of the sandy soil according to the specific gravity method, an electronic balance with the measuring range of 2000-4000 g and the division value of 0.01g is adopted, and a volumetric flask with the volume of 1000mL is adopted.
Further, the temperature is kept consistent during the operation of the step 3 and the step 4.
Further, measuring the temperature of the mixed solution in the step 3 to be T; the step 4 also comprises the following processes: taking n temperature values near the temperature T, respectively adding water with the temperature corresponding to the n temperature values into n identical volumetric flasks to a scale mark A, and respectively weighing the mass of the water; drawing a curve of the mass changing along with the temperature according to the mass obtained at different temperatures; searching the mass m corresponding to the temperature at the moment according to the curve20。
Further, the hydrous soil sample a is prepared according to 5 different proportions in the step 11、a2、a3、a4、a5Repeating the steps 2-6 to respectively calculate the calculated specific gravity Gsc1、Gsc2、Gsc3、Gsc4And Gsc5Then, the arithmetic mean of the calculated specific gravities is taken as the calculated specific gravity Gsc。
Further, a hydrous soil sample1、a2、a3、a4、a5Taking two portions of each hydrous soil sample, calculating the calculated specific gravity of each hydrous soil sample according to the steps 2-6 respectively, and taking the arithmetic average of the 10 calculated specific gravities to obtain the calculated specific gravity Gsc。
Further, in the step 7, the same volumetric flask as used in the steps 1-7 is adoptedA volumetric flask, wherein the mass of the sample is the same as that in the step 2; measuring the temperature T of mixed liquid formed by the sandy soil sample, the volumetric flask and the water which are configured in the process of detecting the water content of the sandy soil according to the hydrometer method1(ii) a According to temperature T1The corresponding mass is looked up from the curve of mass versus temperature.
Furthermore, an electronic balance with the measuring range of 2000-4000 g and the division value of 0.01g is adopted in the process of weighing the mass.
The specific gravity method comprises the following steps:
the method is carried out by adopting the process and formula specified in geotechnical test regulation (SL 237-1999); the method belongs to an off-line detection method, has high detection speed, short detection time compared with a drying method, and high safety compared with an alcohol combustion method; the specific process is as follows:
(1) instrumentation and equipment
Glass bottle: the volume is more than 500 mL;
balance: weighing 1000g, and dividing value 0.5 g;
and others: funnel, spoon, water absorption ball, glass sheet, soil sample plate and glass rod.
The method comprises the following operation steps:
1) taking 200-300 g of a representative sandy soil sample, and putting the sample into a soil sample tray;
2) injecting clear water into a glass bottle to about 1/3 degrees, then pouring the sample in the soil sample tray into the bottle by using a funnel, and stirring for 1-2 min by using a glass rod until the gas is completely discharged;
3) adding clear water into the bottle until the bottle is completely filled, standing for 1min, removing foam with water-absorbing ball, adding clear water to fill the bottle, covering with glass sheet, and wiping off m weighed on the outer wall of the bottle1；
4) Pouring out the mixed liquid in the bottle, cleaning, adding clear water into the bottle until the bottle is completely full of the mixed liquid, covering a glass sheet, wiping the outer wall of the bottle to dry, and weighing to obtain m2；
5) The water content was calculated according to the following formula:
in the formula: omega isWater rate,%; m is the mass of the wet sandy soil sample, g; gs is the actual specific gravity of sandy soil, is measured by a specific gravity bottle and is dimensionless; m is1Is the total mass of the glass bottle, water and sandy soil, g; m is2Is the total mass of the quality bottle and the water, g.
However, the existing specific gravity method has the following defects:
(1) since the moisture content is expressed in percent, it needs to be multiplied by 100 on the right of the formula; through verification, the parameters m and m in the formula1、m2And the result of the water content is changed greatly due to small change of Gs, namely the sensitivity of a formula is high, so that the error of the result of the water content detected by the specific gravity method is more than an allowable value compared with the error of a drying method, and the detection result is not suitable for engineering practice.
(2) The concept expression of the glass bottle in the hydrometric method is not clear, and the type of the glass bottle is not specifically explained; according to four conventional ways, 500mL and 1000mL beakers and measuring cylinders are generally adopted for testing, and the influence of human errors is reduced or eliminated as much as possible in the test; but still can not meet the requirements of actual engineering;
(3) the range of an electronic balance recommended to be used in the hydrometric method is 1000g, the precision is 0.5g, and the precision cannot meet the test requirement;
(4) moreover, it was found through experiments that the density variation of water due to the variation of water temperature has a non-negligible effect in the present experiment, thus leading to different masses of the same substance at the same volume; the specific gravity method is not considered in weighing m1And m2The water temperature is different.
On the basis of the prior art, the invention improves the applicability and the detection precision through creative improvement, improves the test process and the calculation method, reduces the error of the detection result, and the detection result of the invention is close to or equal to the result of the drying method.
And (3) drying:
the process was carried out using the procedure specified in the soil test protocol (SL 237-1999):
the water content is calculated by the following formula:
in the formula: omega is water content,%; m is the mass of the wet sandy soil sample, g; m isdDry soil mass, g.
Examples
The specific process is as follows:
preparing 5 soil samples with representative water content for sandy soil; according to the actual engineering, the water content range of sandy soil is generally within 15%; considering that the calculated specific weight is representative while the workload is reduced, five soil samples with the water contents of 3.0%, 6.0%, 9.0%, 12.0% and 15.0% are prepared for sandy soil;
instrumentation and equipment
Volumetric flask: 2 volumetric flasks with 1000mL of solvent;
an electronic balance: the measuring range is 2000g to 4000g, and the division value is 0.01 g;
an aluminum box: a plurality of the grooves are formed;
oven: one, one.
And others: a thin plastic funnel, an iron trowel, a rubber head dropper, a soil sample plate, a glass rod, a thermometer and the like.
The method comprises the following operation steps:
1) weighing the mass of a plurality of dry aluminum boxes and recording the mass;
2) pouring out the residual moisture in the volumetric flasks to dry the interior of the volumetric flasks as much as possible, simultaneously wiping off the moisture on the outer walls of the volumetric flasks, weighing the volumetric flasks on an electronic balance, and recording the weighing results of the two volumetric flasks;
3) putting 1000g of a representative sandy soil sample into a soil sample tray, weighing a proper amount of clear water according to the required water content, pouring the clear water into the sandy soil sample, and uniformly mixing;
4) respectively putting the uniformly mixed wet sandy soil sample into two volumetric flasks, wherein one flask is 250g, the other flask is 200g, simultaneously respectively weighing 2 parts of 40-50 g of the uniformly mixed wet sandy soil sample, putting the uniformly mixed wet sandy soil sample into a prepared aluminum box, and weighing the total mass of the aluminum box and the wet sandy soil sample;
5) filling clear water into the volumetric flask to about 1/3 times of the volumetric flask, covering a bottle stopper, inclining the volumetric flask, turning over and shaking for about 30s, and observing whether a large amount of bubbles exist at the bottom of the volumetric flask; if yes, continuing to turn over and shake until bubbles at the bottom disappear; standing for 1min, adding water until the water is about 5mm lower than the scale mark, absorbing the bubbles on the surface by using a rubber head dropper after most of the bubbles float to the surface, and adding water until the concave liquid level is flush with the scale mark;
6) covering the volumetric flask, wiping the outer wall of the flask, and weighing the total mass m of the volumetric flask, the sandy soil sample and the water10；
7) Taking out the bottle stopper, suspending the head of the thermometer at the middle part of the volumetric flask, and reading the temperature of the mixed liquid;
8) repeating the steps 2) to 7), and performing tests for determining and calculating specific gravity of the same sandy soil under other water contents;
9) putting the aluminum box filled with the wet sandy soil samples with different water contents into an oven, baking for 6-8 hours, taking out and weighing, and calculating the accurate water contents of the wet sandy soil samples according to the following formula;
in the formula: omega is water content,%; m is the mass of the wet sandy soil sample, g; m isdDry soil mass, g.
10) Cleaning the volumetric flask, filling clear water with different temperatures until the concave liquid level is flush with the scale mark, and taking the temperature of the water as a value near room temperature; the total mass m of the volumetric flask and water is weighed immediately after filling with clear water20And recording; repeating the steps to obtain the mass at different temperatures; fitting the obtained data into a curve of which the mass changes along with the temperature by using a curve; for the masses at other temperatures, the masses can be searched from the curve according to the temperature; because the method is generally used for real-time detection, a certain number of temperature values can be selected to test in the vicinity of room temperature in the process of drawing a curve under general conditions, and the curve is drawn as a curve of the quality changing along with the temperature;
11) bringing in sample dataCalculation of specific gravity GscIn a calculation formula;
obtaining 10 specific gravities of sandy soil under 5 water contents (3.0%, 6.0%, 9.0%, 12.0%, 15.0%) (one water content has two parallel tests, two very close specific gravities can be obtained); the arithmetic mean of the above 10 specific gravities was used as the calculated specific gravity.
By calculating specific gravity GscReplacing the actual specific gravity G of sandy soil in the specific gravity methodsAnd detecting the water content in the sandy soil according to a specific gravity method.
The specific process is as follows:
the instrument equipment comprises:
volumetric flask: 2 volumetric flasks with a volume of 1000 mL;
an electronic balance: the measuring range is 2000g to 4000g, and the division value is 0.01 g;
oven: one, carrying out the following steps;
and others: a thin plastic funnel, a trowel, a rubber head dropper, a soil sample tray, a glass rod, a thermometer and the like;
the method comprises the following operation steps:
1) pouring out the residual moisture in the volumetric flasks to dry the inside of the volumetric flasks as much as possible, simultaneously wiping off the moisture on the outer walls of the volumetric flasks, weighing the volumetric flasks on an electronic balance, and recording the weighing results of the two volumetric flasks;
2) respectively filling the sandy soil sample to be detected into two volumetric flasks, wherein one flask is filled with 250g, and the other flask is filled with 200 g;
3) pouring clear water with the capacity of about 1/3 into the volumetric flask, covering a bottle stopper, inclining the volumetric flask, and turning over and shaking for about 30 s; simultaneously observing whether a large amount of bubbles exist at the bottom of the volumetric flask, and if so, continuing to turn over and shake until the bubbles at the bottom disappear; standing for 1min, adding water until the volume is about 5mm lower than the scale mark, removing the bubbles on the surface with a rubber head dropper after most of the bubbles float to the surface, and adding water until the concave liquid level is flush with the scale mark;
4) cover the bottle stopper with capacity, dry the outer wall of the bottle and weighMeasuring the total mass m of the volumetric flask, the sandy soil sample and the water1；
5) Taking out the bottle stopper, suspending the head of the thermometer at the middle part of the volumetric flask, and reading the temperature of the mixed liquid;
6) according to the measured temperature of the mixed liquid, m corresponding to the volumetric flask is searched20The change curve with temperature is obtained to obtain m2；
7) Substituting the measured parameters into a water content formula calculated by a hydrometer method to obtain the water content detected by the method;
the matters to be noted in the above process are:
(1) through analysis, the small change of each parameter in a calculation formula for detecting the water content of sandy soil can cause large change of a calculation result, so that the scientific and objective requirements are strictly followed in a test, and the artificial influence is reduced;
(2) at present, the meaning of a glass bottle used in the hydrometric method test is not clear, and a high-precision 1000mL volumetric flask is adopted to replace the glass bottle; meanwhile, the electronic balance with the precision of 0.5g specified by the specific gravity method can not meet the test requirement at all, and the electronic balance with the precision of 0.01g is recommended to be used;
(3) the density of the water is lower than 4 ℃ when the temperature of the water is higher than or lower than 4 ℃, and the density of the water is reduced along with the increase of the temperature when the temperature of the water is higher than 4 ℃; below 4 ℃ and above 0 ℃, the density of water increases with increasing temperature; through experiments, the density change of the water caused by the change of the water temperature has non-negligible influence in the experiments; thereby causing the mass of the same volume of water to vary; therefore, m should be determined according to the measurement in each test1To determine m from the temperature of2I.e. measuring m2The temperature of (a) must be in accordance with the measurement m1The temperature is the same; in practice, the water temperature generally fluctuates within a certain range around the room temperature, and a series of common water temperatures m can be measured in advance2Drawing m2Temperature profile forConsulting; thereafter, according to m1Is determined on the curve, corresponding m is determined2；
(4) When water is added to about 1/3 of the volume of the volumetric flask, in order to discharge air bubbles, a bottle stopper is covered, the flask is shaken for about 30s, the flask is kept stand for 2min, water is added until the water is about 5mm lower than the scale mark, and after most of the air bubbles float to the surface, the air bubbles on the surface are sucked by a rubber head dropper; after the bubbles are absorbed, adding water until the concave liquid level of the water is flush with the scale marks; when bubbles on the surface are sucked and removed by a rubber head dropper, the bubbles possibly contain a small amount of sandy soil particles with small particle size; through experimental statistics, the total mass of the small amount of sandy soil is very small and can be ignored;
(5) during the test, the mass of the volumetric flask is weighed, the sandy soil sample to be measured is put into the volumetric flask, and the mass of the flask and the mass of the sand are weighed, so that the mass of the weighed sandy soil sample is determined; the weighed sandy soil sample cannot be put into the material tray in advance, so that the evaporation of water in the sandy soil sample is prevented, and the detection result is influenced;
(6) in practice, for each sandy soil, the calculated specific gravity of each sandy soil needs to be obtained through tests before the method is adopted, and the work is completed in advance to prepare for the subsequent actual water content detection.
Five conventional sandy soils were used as examples for testing according to the procedures of the above examples;
according to the requirements of soil engineering test regulation (SL237-1999), the specific gravity method is applicable to sandy soil with the particle size of less than 5mm, so that the sandy soil is sieved by a 5mm sieve in the process of preparing the soil sample; tests were carried out according to the procedure of the examples to determine the calculated specific gravities of five sandy soils, the results of which were as follows: wherein tables 1-5 are the results of five sandy soil tests, respectively.
TABLE 11 calculated specific gravity of sandy soil
Calculated specific gravity of sandy soil No. 22 in Table
TABLE 33 calculated specific gravity of sandy soil
Calculated specific gravity of sandy soil in Table 44
TABLE 55 calculated specific gravity of sandy soil
From the test data in tables 1 to 5, the average calculated specific gravities of sands nos. 1 to 5 were calculated to be 2.720, 2.694, 2.682, 2.740 and 2.722, respectively; the specific gravity of the sandy soil with the particle size of less than 5mm can be measured by a pycnometer method; the actual specific gravities of the sandy soils of No. 1 to No. 5 can be respectively 2.796, 2.736, 2.745, 2.725 and 2.743 through a pycnometer method test; the results show that the parallel difference between the calculated specific gravity and the actual specific gravity of the five sandy soils is 0.015-0.076, and the average difference is 0.0434; only the No. 4 sandy soil is less than 0.02, the rest four sandy soils are all more than 0.02, and the difference is large; the specification of soil engineering test (SL237-1999) states that the specific gravity measured by the pycnometer method needs to be measured twice in parallel, and the difference between the two parallel is not more than 0.02; it can be seen from the above tests that the difference between the calculated specific gravity and the actual specific gravity of each sandy soil is substantially greater than 0.02, and the difference between the calculated specific gravity and the actual specific gravity is relatively large; the indication that the calculated specific gravity has a different meaning from the actual specific gravity.
In order to further verify the applicability and the accuracy of each determined calculated specific gravity to the same sandy soil under different water contents; preparing soil samples with different water contents, combining the actual engineering,since the water content of sandy soil is generally 15% or less, soil samples having water contents close to 2.5%, 5.0%, 7.5%, 10.0%, 12.5% and 15.0% were prepared and verified; testing the water content of the sandy soil according to the specific gravity method to obtain required parameters; in order to verify that the method has higher precision than the actual specific gravity method, the actual specific gravity G of the sandy soil is usedsAnd calculating specific gravity GscRespectively carrying the water content into a water content calculation formula to obtain the water content of the soil sample of an actual specific gravity method and the water content of the soil sample of the method; the calculation results are shown in tables 6 to 10, wherein ω is the moisture content detection result of the drying method, and ω iscFor the calculation of the pycnometry, i.e. the result of the method of the invention, | ω a is the result of the actual pycnometry, | ωcThe absolute error of the method and the drying method (accurate value) is-omega |, andaand-omega | is the absolute error of the actual specific gravity method and the drying method.
TABLE 61 SAND-EARTH MOISTURE WATER CONTENT BY COMPUTED WEIGHT METHOD AND REAL WEIGHT METHOD
TABLE 72 SAND-EARTH MOISTURE WATER CONTENT BY COMPUTED WEIGHT METHOD AND REAL WEIGHT METHOD
Soil sample water content of No. 83 sandy soil calculated specific gravity method and actual specific gravity method
Soil sample water content of No. 94 sandy soil calculated specific gravity method and actual specific gravity method
TABLE 105 moisture content of sandy soil sample by calculated specific gravity method and actual specific gravity method
When the water content of the sandy soil to be detected is less than 10%, the water content difference value of the two parallel detections is less than or equal to 0.5%; when the water content of the sandy soil to be detected is 10-40%, the difference value of the water content of the two parallel detections is less than or equal to 1%; as can be seen from the data in tables 6 to 10, the results of the method of the invention, namely the calculation of the specific gravity method for detecting the water content of No. 2, 4 and 5 sandy soil simultaneously meet the two requirements, and the results of the detection of No. 1 and 3 sandy soil meet the second requirement and do not meet the first requirement; however, only one of the 6 soil samples of No. 1 and No. 3 sandy soil can not meet the requirement; the absolute error between the result of the water content of the soil sample which does not meet the requirement and the drying method is smaller than the absolute error between the result of the water content of the actual specific gravity method and the drying method, and the partial result of the specific gravity method is very close to the result of the drying method; according to statistics, of 30 groups of data of actual specific gravity method results, 19 groups do not meet the requirements of geotechnical test regulation (SL237-1999), account for 63.3%, and only 11 groups meet the requirements.
According to the principle of related errors in the measurement, under the condition of known true values, the accuracy degree of the measured value and the accurate value can be represented by standard deviation; however, the number in actual measurement is always limited, so that an approximation of the standard deviation found by the incidental errors defining a limited number of measured values in the measurement is called "median error", which is expressed as σ, i.e.:
in the formula: Δ is the occasional error of the measured value from the accurate value, and n is the number of measurements. The sigma can be used for measuring the closeness degree of the result of the hydrometallurgy and the result of the drying method on the whole, and the smaller the sigma is, the closer the sigma is to the accurate result is, and the larger the sigma is, the farther the accurate result is.
Calculating the error between the result of the specific gravity method and the result of the drying method of each sandy soil by adopting the formula; the error in the results of the calculated specific gravity method and the actual specific gravity method by calculating sandy soils nos. 1 to 5 is shown in table 11; as can be seen from the table, for each sandy soil, the median error of the calculated specific gravity method is obviously smaller than that of the actual specific gravity method; the overall result shows that the accuracy of the specific gravity method is obviously superior to that of the actual specific gravity method under the condition of different water contents of the same sandy soil.
TABLE 11 error in the results of the calculated specific gravity method and the actual specific gravity method for five sandy soils
Through the tests, the result of the method for calculating the specific gravity, namely the invention meets the requirement of the detection precision of the water content, and the detection result of partial water content is very close to the result of the drying method; the error between the result of the existing actual specific gravity method and the result of the drying method is large, and most of the results do not meet the precision requirement; moreover, tests show that the method only needs 20min to detect the water content of the sandy soil to be detected; can basically achieve the purpose of real-time detection and has stronger practicability.
For the same sandy soil, the constant quantity is the specific gravity of the sandy soil under different water contents; if only a high-precision volumetric flask and an electronic balance are adopted and the influence of human errors is reduced or eliminated as much as possible in the detection process, the water content result and the error of the drying method still do not meet the requirements; the invention provides a new index-calculation specific gravity GscCalculating the water content by using the calculated specific gravity to replace the actual specific gravity in a calculation formula of a specific gravity method; therefore, the method for rapidly detecting the water content of sandy soil is called a method for calculating specific gravity; in the present invention, the specific gravity G is calculated in advancescIs calculated to obtainThen, carrying out field detection on the water content according to the specific gravity method; the invention can detect the water content of the sandy soil to be detected only in 20 min; compared with a drying method which requires at least 6 hours, the method greatly shortens the detection time, has high detection speed and high precision, and can basically achieve the purpose of real-time detection; meanwhile, the electric energy is saved; the method is suitable for sandy soil with the particle size of less than 5mm, 5 kinds of conventional sandy soil are tested in the later period, and the detection result of the method is compared with the result of a drying method, so that the detection result of the method is very similar to that of the drying method, and the error requirement can be basically met; the invention has good applicability and popularization when detecting the water content of sandy soil with the thickness of less than 5 mm.
Claims (7)
1. A method for detecting the water content of sandy soil is characterized by comprising the following steps:
step 1: taking a sandy soil sample, adding water according to a certain proportion to prepare a water-containing soil sample a;
step 2: taking a volumetric flask, weighing the mass m0Placing the soil sample a in a volumetric flask;
and step 3: adding water into the volumetric flask until the water content is lower than the scale mark A, and adding water until the water content reaches the scale mark A after bubbles are eliminated; weighing the mass m at this moment10；
And 4, step 4: cleaning and drying the volumetric flask, adding water to the volumetric flask to a scale A to obtain the mass m of the volumetric flask plus the water20；
And 5: taking a soil sample a with certain mass, and obtaining the water content omega of the soil sample a by a drying method0；
Step 6: specific gravity G was calculated by the following formulasc：
And 7: will calculate specific gravity GscAnd (3) replacing the actual specific gravity Gs of the sandy soil in the specific gravity method, and detecting the water content in the sandy soil according to the specific gravity method.
2. The method for detecting the moisture content of sandy soil according to claim 1, wherein the temperature is kept consistent during the operation of the step 3 and the operation of the step 4.
3. The method for detecting the water content of sandy soil according to claim 1, wherein the temperature of the mixed solution in the step 3 is measured as T; the step 4 also comprises the following processes: taking n temperature values near the temperature T, respectively adding water with the temperature corresponding to the n temperature values into the same volumetric flask to the scale mark A, and respectively weighing the mass of the water; drawing a curve of the mass changing along with the temperature according to the mass obtained at different temperatures; searching the mass m corresponding to the temperature at the moment according to the curve20。
4. The method for detecting the water content of sandy soil according to claim 1, wherein the water-containing soil sample a is prepared according to 5 different proportions in the step 11、a2、a3、a4、a5Repeating the steps 2-6 to respectively calculate the calculated specific gravity Gsc1、Gsc2、Gsc3、Gsc4And Gsc5Then, the arithmetic mean of the calculated specific gravities is taken as the calculated specific gravity Gsc。
5. The method for detecting the water content of sandy soil according to claim 4, wherein the water-containing soil sample a1、a2、a3、a4、a5Taking two portions of each hydrous soil sample, calculating the calculated specific gravity of each hydrous soil sample according to the steps 2-6 respectively, and taking the arithmetic average of the 10 calculated specific gravities to obtain the calculated specific gravity Gsc。
6. The method for detecting the water content of sandy soil according to claim 3, wherein in the step 7, a volumetric flask which is the same as the volumetric flask used in the steps 1 to 7 is adopted, and the quality of a sampling product is the same as that in the step 2; measuring the temperature T of mixed liquid formed by the sandy soil sample, the volumetric flask and the water which are configured in the process of detecting the water content of the sandy soil according to the hydrometer method1(ii) a According to temperature T1The corresponding mass is looked up from the curve of mass versus temperature.
7. The method for detecting the water content of the sandy soil according to claim 1, wherein an electronic balance with the measuring range of 2000-4000 g and the division value of 0.01g is adopted in the process of weighing the sandy soil.
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