Method for solidifying farmland drainage ditch slope by utilizing microorganism induced calcium carbonate
阅读说明：本技术 一种利用微生物诱导碳酸钙固化农田排水沟坡面的方法 (Method for solidifying farmland drainage ditch slope by utilizing microorganism induced calcium carbonate ) 是由 缴锡云 李焕弟 李江 巫纾予 于 2021-07-05 设计创作，主要内容包括：本发明提供了一种利用微生物诱导碳酸钙固化农田排水沟坡面的方法,属于农田排水沟固化技术领域,所述方法包括以下步骤：1)采集农田排水沟坡面的土壤,测定所述土壤的含水率θ-0、土壤干密度ρ-d；2)将所述采集农田排水沟坡面的土壤分层压实达到预设土壤干密度ρ-(d’)；测定田间持水量θ-(max),根据公式计算出土壤孔隙度n；3)根据公式L＝a×b×H(θ-(max)-θ-0)n×100计算出L的具体值；L为巴氏芽孢杆菌菌液的体积和/或固结液的体积；4)向所述农田排水沟坡面喷洒巴氏芽孢杆菌菌液后,喷洒固结液；5)每隔15～18h重复步骤4)中的操作一次,重复的次数为7～10次。所述方法能够实现农田排水沟生态固化。(The invention provides a method for solidifying a slope surface of a farmland drainage ditch by utilizing microorganism-induced calcium carbonate, belonging to the technical field of solidification of farmland drainage ditches, and comprising the following steps of: 1) collecting soil on the slope of a farmland drainage ditch, and determining the water content theta of the soil 0 Dry density of soil rho d (ii) a 2) The soil on the slope surface of the collected farmland drainage ditch is compacted in a layered mode to reach the preset soil dry density rho d' (ii) a Determination of field Water holding Capacity θ max Calculating the soil porosity n according to a formula; 3) according to the formula L ═ a × b × H (θ) max ‑θ 0 ) n × 100 calculating a specific value of L; l is the volume of the bacillus pasteurii bacterial liquid and/or the volume of the consolidation liquid; 4) spraying a bacillus pasteurii bacterial liquid on the slope surface of the farmland drainage ditch, and then spraying a consolidation liquid; 5) repeating every 15-18 hThe operation in the step 4) is carried out once, and the repeated times are 7-10 times. The method can realize ecological solidification of the farmland drainage ditch.)
1. A method for solidifying a slope surface of a farmland drainage ditch by utilizing microorganism-induced calcium carbonate comprises the following steps:
1) collecting soil on the slope of a farmland drainage ditch, and determining the water content theta of the soil0Dry density of soil rhodWherein, the initial water content (volume) is controlled to be 15-20%;
2) the soil on the slope surface of the collected farmland drainage ditch is compacted in a layered mode to reach the preset soil dry density rhod'; then, the field water holding capacity theta is measured according to the ring knife methodmaxAccording to the formula n (%) ═ 93.947-32.995 ρd' calculating the porosity n of the soil;
3) according to the formula L ═ a × b × H (θ)max-θ0) n × 100 calculating a specific value of L; wherein a and b are respectively the length of the soil containerAnd width, H is the depth of cure; in the solidification treatment process, L is the volume of the bacillus pasteurianus bacterial liquid, the volume of the consolidation liquid or the total volume of the bacillus pasteurianus bacterial liquid and the consolidation liquid; the volume ratio of the pasteurella bacteria liquid to the consolidation liquid is (2-5) to 3;
4) spraying a bacillus pasteurii bacterial liquid on the slope surface of the farmland drainage ditch for 6-9 hours, and then spraying a consolidation liquid;
5) repeating the operation in the step 4) once every 15-18 h, wherein the repetition frequency is 7-10 times;
the consolidation liquid is a mixed solution of urea and calcium chloride, and the quantity ratio of urea to calcium chloride in the mixed solution is 1: 1.
2. The method according to claim 1, wherein the preset soil dry density p in step 2)d' is 1.4 to 1.5g/cm3。
3. The method according to claim 1, wherein the soil on the farmland drainage slope in the step 1) is collected and sieved, and the mesh size of the sieved mesh is 2 mm.
4. The method according to any one of claims 1 to 3, wherein the depth of the curing in step 3) is 4 to 6 cm.
5. The method according to claim 1, wherein the concentration of the consolidation fluid in the step 3) is 1.0-2.0 mol/L in terms of calcium chloride.
6. The method as claimed in claim 1, wherein the volume ratio of the pasteuria bacillus liquid to the consolidation liquid in step 3) is 2: 3.
7. The method according to claim 1, wherein the bacillus pasteurii in step 3) has the deposit number ATCC 11859; the pasteuria bacillus is capable of producing urease.
8. The method of claim 1, wherein the water cut θ in step 1)015 to 20 percent.
Technical Field
The invention belongs to the technical field of solidification of farmland drainage ditches, and particularly relates to a method for solidifying a slope surface of a farmland drainage ditch by utilizing microorganism-induced calcium carbonate.
Background
Agricultural irrigation and drainage engineering directly influence the field irrigation quality, and the field escape canal is the basic constitution of agricultural drainage engineering, and its drainage function is the important guarantee of agricultural production. The leakage loss amount of the traditional soil drainage ditch is large, and the side slope has the problems of easy collapse, easy soil erosion and the like. Therefore, the solidification of the side slope of the farmland drainage ditch is an important foundation for the development of agriculture. The farmland drainage ditch is reinforced mainly by engineering measures, biological measures and material measures at present, but the measures have the defects of complicated construction, high cost, difficult maintenance and the like.
In recent years, the technology of microorganism-induced calcium carbonate precipitation (MICP) is developed rapidly, and the principle is that microorganisms metabolize to generate urease, the urease catalyzes urea to hydrolyze to generate carbonate ions, and the carbonate ions are combined with exogenous calcium ions to form calcium carbonate crystals with a consolidation effect, so that the solidification of rock and soil is realized. The MICP technology is simple to operate, does not generate toxic and harmful substances, has better durability, and is a more ecological and friendly soil body reinforcing technology. At present, the technology is mostly applied to the technical field of geotechnical engineering, and the application of the technology to the fixation of the soil drainage slope is not reported.
Disclosure of Invention
In view of the above, the present invention provides a method for solidifying a slope surface of a farmland drainage ditch by using calcium carbonate induced by microorganisms; the method can realize ecological solidification of the farmland drainage ditch, replace concrete solidification of the farmland drainage ditch, and realize the technical effects that the farmland drainage ditch can permeate water, can reduce water stains, and uses less or does not use concrete.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a method for solidifying a slope surface of a farmland drainage ditch by utilizing microorganism-induced calcium carbonate, which comprises the following steps:
1) collecting soil on the slope of a farmland drainage ditch, and determining the water content theta of the soil0Dry density of soil rhod；
2) Subjecting the coal mining toThe soil layering compaction of the farmland drainage ditch slope surface is collected to reach the preset soil dry density rhod'; determining the field water capacity theta according to the cutting ring methodmaxAccording to the formula n (%) ═ 93.947-32.995 ρd' calculating the porosity n of the soil;
3) according to the formula L ═ a × b × H (θ)max-θ0) n × 100 calculating a specific value of L; wherein a and b are respectively the length and width of the soil container, and H is the depth of solidification; in the solidification treatment process, L is the volume of the bacillus pasteurianus bacterial liquid, the volume of the consolidation liquid or the total volume of the bacillus pasteurianus bacterial liquid and the consolidation liquid;
4) spraying a bacillus pasteurii bacterial liquid on the slope surface of the farmland drainage ditch for 6-9 hours, and then spraying a consolidation liquid;
5) repeating the operation in the step 4) once every 15-18 h, wherein the repetition frequency is 7-10 times;
the consolidation liquid is a mixed solution of urea and calcium chloride, and the quantity ratio of urea to calcium chloride in the mixed solution is 1: 1.
Preferably, the preset dry density ρ of the soil in the step 2)d' is 1.4 to 1.5g/cm3。
Preferably, the soil on the slope surface of the farmland drainage ditch in the step 1) is screened after being collected, and the aperture of the screened screen is 2 mm.
Preferably, the curing depth in the step 3) is 4-6 cm.
Preferably, the concentration of the consolidation liquid in the step 3) is 1.0-2.0 mol/L calculated by calcium chloride.
Preferably, the volume ratio of the bacillus pasteurianus bacterial liquid to the consolidation liquid in the step 3) is 2: 3.
Preferably, the Bacillus pasteurianus in step 3) has the deposit number ATCC 11859; the pasteuria bacillus is capable of producing urease.
Preferably, the water content θ in step 1)015 to 20 percent.
According to the method for solidifying the slope surface of the farmland drainage ditch by utilizing the microorganism induced calcium carbonate, the total volume L of reagents (the pasteurella bacteria liquid and/or the consolidation liquid) required when the water capacity of the farmland is reached is calculated according to the standard of the water capacity of the farmland, and the pasteurella bacteria liquid and the consolidation liquid are sprayed according to the proportion of (2-5) to (3), so that the yield of the calcium carbonate can be improved, the material consumption is greatly saved, and the cost is reduced.
The bacillus pasteurianus has the functions of producing urease through metabolism and exciting urea in consolidation liquid to perform hydrolysis reaction: NH generated4 +The pH of the solution is raised to allow HCO to form3 -With CaCl in the consolidation fluid2Ca provided2+After meeting to produce CaCO3And (3) crystallization and deposition: produced CaCO3One part of the crystal is attached to the surface of the soil particles to connect adjacent soil particles together, and the other part of CaCO3The crystals are filled in soil pores, so that the porosity and permeability of the soil are reduced to a certain extent, and compared with concrete reinforcement, the method provided by the invention can still play a certain stain reducing role and has no negative influence on the environment.
Drawings
FIG. 1 shows the amount of calcium carbonate produced in the solidified soil.
Detailed Description
The invention provides a method for solidifying a slope surface of a farmland drainage ditch by utilizing microorganism-induced calcium carbonate, which comprises the following steps: 1) collecting soil on the slope of a farmland drainage ditch, and determining the water content theta of the soil0Dry density of soil rhod(ii) a 2) The soil on the slope surface of the collected farmland drainage ditch is compacted in a layered mode to reach the preset soil dry density rhod'; determining the field water capacity theta according to the cutting ring methodmaxAccording to the formula n (%) ═ 93.947-32.995 ρd' calculating the porosity n of the soil; 3) according to the formula L ═ a × b × H (θ)max-θ0) n × 100 calculating a specific value of L; wherein a and b are respectively the length and width of the soil container, and H is the depth of solidification; in the solidification treatment process, L is the volume of the bacillus pasteurianus liquid and the volume of the consolidation liquid or the total volume of the bacillus pasteurianus liquid and the consolidation liquid, and the volume ratio of the bacillus pasteurianus liquid to the consolidation liquid is (2-5): 3; 4) spraying a bacillus pasteurii bacterial liquid on the slope surface of the farmland drainage ditch for 6-9 hours, and then spraying a consolidation liquid; 5) repeating the steps every 15-18 h4) The operation is carried out once, and the repeated times are 7-10 times.
In the invention, firstly, soil on the slope of a farmland drainage ditch is collected, and the water content theta of the soil is measured0Dry density of soil rhod. The slope surface of the farmland drainage ditch is not specially limited, and the slope surface of the farmland drainage ditch can be conventional in the field. In the invention, the soil on the slope of the farmland drainage ditch is preferably screened after being collected, and the aperture of the screened screen is preferably 2 mm. The specific operation of the sieving in the invention is not particularly limited, and the conventional sieving operation in the field can be adopted. In the present invention, the water content θ of the soil0Preferably, the determination is carried out by adopting a drying method; the dry density of the soil rhodPreferably, the measuring is carried out by a ring cutter method; the field water holding capacity thetamaxPreferably by the ring knife method. In the present invention, the water content θ of the soil0Preferably 15-20%, and the water content of the soil is volume percent.
In the invention, the soil on the slope of the farmland drainage ditch is compacted in a layered manner to reach the preset dry soil density rhod'; determining the field water capacity theta according to the cutting ring methodmaxAccording to the formula n (%) ═ 93.947-32.995 ρd' calculate soil porosity n. In the present invention, the predetermined soil dry density ρd' preferably 1.4 to 1.5g/cm3. In the specific implementation process of the invention, the soil is preferably filled into a container for layering compaction; the container can be a transparent organic glass box; the specification of the container can be selected as follows: the length, width and height are 12X 12cm (thickness 0.35 cm); in the invention, the filling height of the soil is preferably 6-8 cm, and more preferably 6 cm; the thickness of each layer is preferably 1 cm.
In the present invention, the formula L is a × b × H (θ)max-θ0) n x 100 calculates the total volume L of reagents (pasteurella bacteria liquid and/or consolidation liquid) required for the solidification treatment when the field water capacity is reached. In the present invention, the formula L is a × b × H (θ)max-θ0) nx100 is evolved from an irrigation quota formula recorded in irrigation and water conservancy; for soil without being influenced by underground waterThe maximum amount of moisture indicator can be maintained. In the invention, a and b are respectively the length and the width of the soil container, H is the curing depth, and the curing depth is preferably 4-6 cm, more preferably 4 cm; in the invention, the volume ratio of the pasteurella bacteria liquid to the consolidation liquid is (2-5) to 3, and can be selected from 2:3, 1:1, 4:3 and 5: 3; the ratio of calcium carbonate production rate to material usage is preferably 2: 3.
In the present invention, the Bacillus pasteurianus has the deposit number ATCC 11859; the bacillus pasteurianus is capable of producing urease; the culture method of the pasteurella is not particularly limited in the present invention, and the conventional culture method of the pasteurella in the art can be adopted, and the specific description of the examples of the present invention is provided.
In the invention, the consolidation liquid is a mixed solution of urea and calcium chloride, and the amount ratio of urea to calcium chloride in the mixed solution is 1: 1. In the invention, the concentration of the consolidation liquid is preferably 1.0-2.0 mol/L, and more preferably 1 mol/L.
According to the calculation result, spraying the bacillus pasteurii bacterial liquid to the slope of the farmland drainage ditch for 6-9 hours, and then spraying the consolidation liquid. In the invention, the spraying is preferably carried out for a small number of times, and the spraying times and the spraying amount are not particularly limited so as not to generate surface effusion and ensure that the bacteria liquid is completely infiltrated into the soil. In the invention, preferably, after the bacillus pasteurianus liquid is sprayed for 6 hours, a consolidation liquid is sprayed; the spraying mode of the consolidation liquid is consistent with that of the bacillus pasteurii bacterial liquid, and the details are not repeated here.
In the invention, the operation in the step 4) is preferably repeated every 15-18 h, more preferably every 18h, and the number of times of repetition is 7-10 times, and can be selected from 7 times, 8 times, 9 times or 10 times. In the present invention, after repeating the treatment 7 times, the amount of calcium carbonate produced in the solidified soil is preferably measured by a hydrochloric acid immersion method, and the number of the subsequent solidification treatments is determined according to the solidification effect.
The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
And (3) strain culture:
bacillus pasteurii (Sporosarcinapasturii, American type culture Collection ATCC 11859), the liquid medium of which has the following formulation: yeast extract 20g/L, (NH)4)2SO410g/L，MnSO4·H2O 10mg/L，NiCl·6H2O24 mg/L and distilled water 1000g/L, the above components were mixed uniformly, and the pH of the liquid medium was adjusted to 8.5 with 1mol/L NaOH solution. Putting a magnetic stirrer into a liquid culture medium in advance, performing high-temperature sterilization and ultraviolet sterilization on the magnetic stirrer, inoculating activated bacteria into the culture medium on a sterile operating platform, finally moving the culture medium onto a heating plate of the magnetic stirrer, adjusting the rotating speed to 250rpm, and culturing at 30 ℃ until the liquid is turbid and the optical density OD of the bacteria is higher than that of the bacteria600Reaching 0.9499.
Example 1
Step 1, taking soil, and measuring initial water content theta of the soil0Dry density of soil rhodControlling the initial water content of the soil to be 15-20%; the specific method comprises the following steps:
the determination method comprises the following steps:
1) the instrument equipment comprises: oven, electronic balance, dryer, weighing box (aluminum box)
2) The operation steps of [ note: performing triplicate determinations
Firstly, taking a representative soil sample of 15-20 g, putting the sample into an aluminum box with known weight, immediately covering a box cover, and weighing to obtain the mass of wet soil and the mass of the aluminum box.
And secondly, uncovering the box cover, putting the sample and the aluminum box into an oven, and drying the sample and the aluminum box to constant weight at 105-110 ℃.
Taking out the dried sample and the aluminum box, covering the box cover, putting the sample and the aluminum box into a dryer, cooling to room temperature, weighing to obtain the dry soil mass and the aluminum box mass, and weighing to the precision of 0.01 g.
3) Initial moisture content ═ mass of wet soil + mass of aluminum box) - (mass of dry soil + mass of aluminum box) ]/[ (mass of dry soil + mass of aluminum box) -mass of aluminum box ] ═ mass of water/mass of dry soil.
If the initial water content is 15% to 20%, it is used as it is, and if it is not in this range, it is allowed to fall within this range by air-drying or by adding water.
The initial water content of the soil sample was measured to be 19.61%, and used as it is.
Step 2, measuring the field water capacity theta by a ring cutter methodmaxThe content was found to be 35.84%. Loading the soil sample into a transparent organic glass box with length, width and height of 12 × 12 × 12cm (thickness of 0.35cm), controlling the loading height at 6cm, and compacting by layers until the dry density of the soil is 1.4g/cm3. Soil porosity n (%) ═ 93.947-32.995 rhod'＝3.947-32.995×1.4＝47.75％；
And 3, setting the soil solidification depth H to be 4cm, and setting the soil solidification depth H to be 11.3 multiplied by H (theta) according to a calculation formula Lmax-θ0) n × 100 to 11.3 × 11.3 × 0.04 × (35.84% -19.61%) × 47.75% to 100 to 39.58ml, and the total amount (volume) L of the bacillus pasteurii bacterial liquid and the consolidation liquid (mixed solution of urea and calcium chloride) required by one-time solidification treatment when the field water capacity is reached is calculated to be 39.58ml, wherein the spraying dosage (volume) ratio of the bacillus pasteurii bacterial liquid to the consolidation liquid is 2: 3;
step 4, uniformly spraying 2/5L of pasteurella bacteria liquid on the surface of the soil by adopting a method of a small amount of times;
step 5, after the spraying of the pasteurella bacteria liquid is finished and the liquid is kept stand for 6 hours, 3/5L of 1.0mol/L consolidation liquid is sprayed on the surface layer of the soil uniformly for a plurality of times in a small amount;
and 6, according to the curing treatment methods in the steps 4 and 5, curing treatment is carried out once every 18 hours, and after 7 times of curing treatment, the generation amount of calcium carbonate of the cured soil sample is measured by a hydrochloric acid soaking method, so that the curing effect is judged. With the increase of the curing rounds, the generation amount of calcium carbonate is in a trend of increasing rapidly at first and then slowly, and the generation amount of calcium carbonate reaches 3.02 percent after 7 rounds of curing treatment.
Example 2
Step 1, taking soil, and measuring initial water content theta of the soil0Dry density of soil rhodControlling the initial water content of the soil to be 15-20%;
the specific method comprises the following steps:
the determination method comprises the following steps:
1) the instrument equipment comprises: oven, electronic balance, dryer, weighing box (aluminum box)
2) The operation steps of [ note: performing triplicate determinations
Firstly, taking a representative soil sample of 15-20 g, putting the sample into an aluminum box with known weight, immediately covering a box cover, and weighing to obtain the mass of wet soil and the mass of the aluminum box.
And secondly, uncovering the box cover, putting the sample and the aluminum box into an oven, and drying the sample and the aluminum box to constant weight at 105-110 ℃.
Taking out the dried sample and the aluminum box, covering the box cover, putting the sample and the aluminum box into a dryer, cooling to room temperature, weighing to obtain the dry soil mass and the aluminum box mass, and weighing to the precision of 0.01 g.
4) Initial moisture content ═ mass of wet soil + mass of aluminum box) - (mass of dry soil + mass of aluminum box) ]/[ (mass of dry soil + mass of aluminum box) -mass of aluminum box ] ═ mass of water/mass of dry soil.
If the initial water content is 15% to 20%, it is used as it is, and if it is not in this range, it is allowed to fall within this range by air-drying or by adding water.
The initial water content of the soil sample was measured to be 19.61%, and used as it is.
Step 2, filling the soil sample into a transparent organic glass box with the length multiplied by the width multiplied by the height multiplied by 12cm (the thickness is 0.35cm), controlling the filling height to be 6cm, and carrying out layered compaction until the dry density of the soil is 1.4g/cm3；
Step 3, the soil solidification depth H is 4cm, the volume L of the pasteurella bacteria liquid required by one-time solidification treatment when the field water capacity is reached is calculated to be 39.58ml, the spraying volume ratio of the pasteurella bacteria liquid to the consolidation liquid is 2:3, and the volume of the consolidation liquid obtained by calculation is 59.37 ml;
step 4, uniformly spraying 39.58ml of pasteurella bacteria liquid on the surface of the soil by adopting a method of a small amount of times;
step 5, after the spraying of the pasteurella bacillus liquid is finished and the solution is kept stand for 6 hours, 59.37ml of 1.0mol/L consolidation solution is sprayed on the surface layer of the soil uniformly for a plurality of times in a small amount;
and 6, according to the curing treatment methods in the steps 4 and 5, curing treatment is carried out once every 18 hours, and after 7 times of curing treatment, the generation amount of calcium carbonate of the cured soil sample is measured by a hydrochloric acid soaking method, so that the curing effect is judged. With the increase of the curing rounds, the generation amount of calcium carbonate tends to increase rapidly and then slowly, and after 7 rounds of curing treatment, the generation amount of calcium carbonate reaches 4.54%.
Example 3
Step 1, taking soil, and measuring initial water content theta of the soil0Dry density of soil rhodControlling the initial water content of the soil to be 15-16%; the specific method comprises the following steps:
the determination method comprises the following steps:
1) the instrument equipment comprises: oven, electronic balance, dryer, weighing box (aluminum box)
2) The operation steps of [ note: performing triplicate determinations
Firstly, taking a representative soil sample of 15-20 g, putting the sample into an aluminum box with known weight, immediately covering a box cover, and weighing to obtain the mass of wet soil and the mass of the aluminum box.
And secondly, uncovering the box cover, putting the sample and the aluminum box into an oven, and drying the sample and the aluminum box to constant weight at 105-110 ℃.
Taking out the dried sample and the aluminum box, covering the box cover, putting the sample and the aluminum box into a dryer, cooling to room temperature, weighing to obtain the dry soil mass and the aluminum box mass, and weighing to the precision of 0.01 g.
5) Initial moisture content ═ mass of wet soil + mass of aluminum box) - (mass of dry soil + mass of aluminum box) ]/[ (mass of dry soil + mass of aluminum box) -mass of aluminum box ] ═ mass of water/mass of dry soil.
If the initial water content is 15% to 20%, it is used as it is, and if it is not in this range, it is allowed to fall within this range by air-drying or by adding water.
The initial water content of the soil sample was measured to be 19.61%, and used as it is.
Step 2, filling the soil sample into a transparent organic glass box with the length multiplied by the width multiplied by the height multiplied by 12cm (the thickness is 0.35cm), controlling the filling height to be 6cm, and carrying out layered compaction until the dry density of the soil is 1.4g/cm3；
Step 3, the soil solidification depth H is 4cm, the volume L of consolidation liquid (mixed solution of urea and calcium chloride) required by primary solidification treatment is calculated to be 39.58ml when the field water capacity is reached, the spraying volume ratio of the bacillus pasteurii bacterial liquid to the consolidation liquid is 2:3, and the volume of the obtained bacillus pasteurii bacterial liquid is calculated to be 26.39 ml;
step 4, uniformly spraying 26.39ml of pasteurella bacteria liquid on the surface of the soil by adopting a method of a small amount of times;
step 5, after the spraying of the pasteurella bacteria liquid is finished and the liquid is kept stand for 6 hours, 39.58ml of 1.0mol/L consolidation liquid is sprayed on the surface layer of the soil uniformly for a plurality of times in a small amount;
and 6, according to the curing treatment methods in the steps 4 and 5, curing treatment is carried out once every 18 hours, and after 7 times of curing treatment, the generation amount of calcium carbonate of the cured soil sample is measured by a hydrochloric acid soaking method, so that the curing effect is judged. With the increase of the curing rounds, the generation amount of calcium carbonate is in a trend of increasing rapidly at first and then slowly, and the generation amount of calcium carbonate reaches 3.49 percent after 7 rounds of curing treatment.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
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