Comparison of different methods to evaluate California Bearing Ratio in sylvan (Native to Iran).
Entering the 21 century forest management has to undergo changes aimed at sustainability of the use of limited natural resources. Differentiation of forestry technologies throughout the production process according to natural conditions of forest stands is a necessary step in such an attempt [3,4]. The most obvious conflict between forestry technologies and forest management are removal of tree cover, movement of timber and heavy machinery through forest stands influence all other parts of the forest ecosystem. Forest practices on steep potentially unstable terrain have evolved over the past 30 years [19, 20, 21]. Unstable terrain, improved water management along roads and simply the awareness and avoidance of unstable terrain the California--Bearing Ratio(CBR) test is frequently used in the assessment of granular materials in base, sub base and sub grade layers of road and air field pavements [5, 6]. The CBR test was originally developed by the California state Highway department and was there after incorporated by the army corps of engineers for the design of flexible pavements. It has become so globally popular that it is incorporated in many subject [1,7,22]. The California Bearing Ratio (CBR) is a penetration test for evaluation of the mechanical strength of road subgrades and base courses. It was developed by the California department of transportation before World War II. The test is performed by measuring the pressure requires to penetrate a soil sample with a plunger of standard area [11, 14]. The measured pressure is then divided by the pressure required to achieve an equal penetration on a standard crushed rock material. The CBR test is described is ASTM standards D1883-05 (for laboratory-prepared samples) and D4429 (for soils in place in field), and AASHTO T193. The CBR test is fully described in BSB77. Soils for civil engineering purposes: part4, compaction related tests. The CBR rating was developed for measuring the load-bearing capacity of soils used for building roads. The CBR can also be used for measuring the load -bearing capacity of unimproved airstrips or for soils under paved airstrips. The harder the surface, the higher the CBR rating. A CBR of 3 equates to tilled farmland, a CBR of 4.75 equates to turf or moist clay, while moist sand may have a CBR of 10 high quality crushed rock has a CBR over 80, the standard material for this test is crushed [12, 15]. California limestone which has a value of 100. Unbound earth materials (e.g., soils, gravels. etc) have an important role in the design and construction of road and airfield pavements or foundation and other earth-fill structures. The assessment of the in situ properties of these materials (i.e., when they exist as bases, subbases or subgrades) in terms of density, strength, etc, is important, as well. However the evaluation of compacted fill is an expensive and time consuming endeavor and, therefore, the testing of these materials is generally quite limited [13, 16, 17]. In addition, the high variability encounter with most natural soil types and the number of soil types typically existing in a project necessitate the presence of a test method that is expensive and rapid. Consequently, the trade-off has been either a cursory survey with limited results or an in-depth assessment but on a limited number of sites [2,8]. The California Bearing Ratio (CBR) test is frequently used in the assessment of granular materials in base, sub base and sub grade layers of road and airfield pavements. The CBR test was originally developed by the California state Highway department and was thereafter incorporated by the army corps of engineers for the design of flexible pavement [9, 10]. It has become so globally popular that it is incorporated in many integrating standards. The California Bearing Ratio (CBR) test is a simple strength test that compares the bearing capacity of a material with that of a well-graded crushed stone (thus, a high quality crushed stone material should have a CBR 100%) it is primarily intended for, but not limited to, evaluating the strength of cohesive materials having maximum particle sizes less than 19 mm (0.75)(AASHTO, 2000). It was developed by the California Division of Highways around 1930 and was subsequently adopted by numerous states, counties, U.S federal agencies and internationally [18, 23]. As a result, most agency and commercial geotechnical laboratories in the U.S are equipped to perform CBR tests. The basic CBR test involves applying load to a small penetration piston at a rate of 1.3 mm (0.05) per minute and recording the total load at penetrations ranging from 0.64 mm (0.025 in.) up to 7.62 mm (0.300 in).
MATERIALS AND METHODS
In order to comparision of different methods to evaluate California bearing ratio in sylvan, an experiment was treatried out in parcel 22 from series 7 of haraz_amol basin according to 5 FAO classified soil groups with 15 samples. The design was laid out in completely block design. Three different methods including labratory results using pentrometer methods and CBR% classification are compared in this research. The area of considered parcel was 52.3 hectares and 43.2 hectares of this area is qualified for utilization and forestry activities the altitude datum in student parcel is between 270 and 420 meters. According to slope classification, 518% of parcel surface has the slope about 31% to 61% the type of parcels original stone is limy kanelgomeray. Forest stand is beech--chestnut and its important tree species are beech--chestnut, azedarahch, anjili, buddleia, and alder. And two kinds of medlar and hawthorn were observed under the ashkoob (storey) as important plant species, we can pain to koole khas. Siklaman bracken, karkas, viola and raspberry. In this research we had to obtain different soil groups based on FAO classification and from among 14 different groups of soil tissue which were set in 6different soil classes in mentioned table.
So, with due attention to primary studies in slightly zone, at least 14 samples of soil should have been prepared and the amount of every soil sample was considered based on relation (1).
Relation(1) 200D < w < 600D
D: diagonal of soil particles to millimeter W: weight of soil to gram
With due attention to above relation, the weight of each sample should be about 0/5 to 5 kilograms. Since samples should have been used in CBR-test, then all samples were prepared in 5 kilograms weight.
Prepared soil samples were sent to laboratory to determine soil tissue, and after soil tissue determination, based on table(1) of different soil group, the needed tests were done. These tests are consist of:
1--particle size analysis with AASHTO 72-27 for macro granule soils.
2--hydrometer analysis with AASHTO 72-88 for micro granule soils. --california bearing ratio(CBR) evaluation methods :
A: CBR evaluation based on USCS classification tables :
After determining soil type based on USCS classification tables in USCS system, the amount of bearing ratio for different soils was recognized and explanted as evidential data. B: CBR evaluation in laboratory:
With due attention to soil samples which had been sent to the laboratory for the purpose of soil tissue determination, CBR test was done after determining the tissue of the soil. It should be mentioned that 4 samples were prepared for esch soil groups: C: square methods of CNR evaluation(pentrometer):
This evaluation was done through fixed intrusion test with conical pentrometer device. For each device, a specific relation was evaluated to calculate soil bearig based on [kg.sup.f]/[cm.sup.2] or kpa. In each relation. Proportion = 1[kg.sup.f]/[cm.sup.2] 98kpa was confimed.
Relation of pericape and soil toleration for micro conic * : y = 0/0102033 x- 0/003 relation (2)
Relation of pericope and soil toleration for macro conic ** : y = 0/020406 x- 0/003 relation (3)
* Micro conic : a conic with section surface for about 3/23 [cm.sup.2] which is used for lands with middle and macro analysis.
** Macro conic : a conic with section surface for about 6/45 [cm.sup.2] which is used for lands with micro analysis. Conic angle in both kinds is 30 degree and intrusion rate is 1cm in every second.
At this method and at the range of soil samples, the tests were done 4 times with specific distances and in 5, 10, 15 and 20 cm depth.
At this research, tow different methods of CBR evaluation were studied and compared with evaluated amount of CBR exploited from classification table in uses system and these methods were in the from of a model with a complete random block.
With due attention to this fact that these 3 variants are comparable in a model of complete random block, so for each one of the treats(3 different methods), 3repetitions were considered in which variance analyzation was done with F-test at (1% and 5%) and Mean comparison was done with LSD-test.
Obtained results from calculation for each different groups of soil is as follow: The soil of "sand and pebble" group
Table 2: CBR evaluation in different methods of soil of "sand and peeble" group. Treat control Penterometer Laboratory Repetition 1 82/5 84/3 81/64 2 85 86/25 82/45 3 83 78/75 79/02 Tables 3: Variance analyzation for soil of sand and peeble group. Change resource ss df Ms=[s.sup.2] F Treat(T) 6/75 2 3/375 2/547 Black(R) 43/91 2 21/955 16/57 ** Error(E) 5/3 4 1/325 General(G) 55/96 8 -- Change resource [F.sub.5%] [F.sub.1%] Treat(T) 3/88 6/99 Black(R) 3/88 6/99 Error(E) General(G) ** signification at 1% percentage level
With due attention to Fs of the table 1% and 5%), we can conclude that there isn't any significant difference between different cores. But the difference between blocks is signification. And it means that blocks are not properly arranged or election situation (choosing situation) in implementational operation of sampling was not equal.
Soil of "gravel" group:
Table 4: Evaluating CBR amount in different methods of soil of "gravel" group. Treat control Penterometer Laboratory Repetition 1 47/5 52/2 46/75 2 42/5 45/45 42/85 3 45 48/75 43/68 Table 5: Variance analyzation for soil of "gravel" group. Change resource ss df Ms=[s.sup.2] F Treat(T) 33/896 2 16/948 26/316 ** Black(R) 41/138 2 20/569 31/936 ** Error(E) 2/576 4 0/644 General(G) 77/61 8 Change resource [F.sub.5%] [F.sub.1%] Treat(T) 3/88 6/99 Black(R) 3/88 6/99 Error(E) General(G) ** signification at 1% of precentage level
With due attention to Fs of the table(1% and 5%) we can conclude that there is significant difference between treats and different blocks. Because the effects of treats are significant, we tend to compare the Mean. Because there is a specific control between the samples, we used LSD-test to compare Meance and result of treats.
With due attention to calculated d' at (1% and 5%) level equal to 1/95 and 2/90, it got clear that results from pentrometer have significant difference with result of laboratory and control in mentioned levels.
<< d' >> : s[bar.d] = [square root of (3[M.sub.s]E/2)]
[d'.sub.x] = s[bar.d] x [t.sub.([varies], df)]
The soil of loomi group with macro tissue:
Table 7: CBR evaluation in different methods of loomi group with macro tissue. Treat control Penterometer Laboratory Repetition 1 27/5 30/75 28 2 25 27 24/75 3 22/5 24 18/78 Table 8: Variance analyzation for soil of loomi group with macro tissue. Change resource ss df Ms=[s.sup.2] F Treat(T) 16/54 2 8/27 5/09 * Black(R) 16/94 2 38/47 23/10 ** Error(E) 6/49 4 1/653 General(G) 99/97 8 Change resource [F.sub.5%] [F.sub.1%] Treat(T) 3/88 6/99 Black(R) 3/88 6/99 Error(E) General(G)
With due attention to Fs of the table(1% and 5%), it is conclude that is a great significant different between treats at 5% level and blocks in 1% and 5% level.
With due attention to calculated d' at 5% level. equal to 3/099, it got clear that result from pentrometer have no significant different with result of laboratory and control. The soil of loomi group with macro tissue
Table 10: The evaluation of CBR amount in different methods of soil of loomi group with macro tissue. Treat control Penterometer Laboratory Repetition 1 6/5 7/5 6/85 2 17 19/5 17/48 3 16/5 18/15 16/48 Table 11: Variance analyzation for soil of loomi group with micro tissue. Change resource ss df Ms=[s.sup.2] F Treat(T) 224/73 2 112/365 591/39 ** Black(R) 5/11 2 2/55 13/42 ** Error(E) 0/76 4 0/19 General(G) 230/6 8 -- Change resource [F.sub.5%] [F.sub.1%] Treat(T) 3/88 6/99 Black(R) 3/88 6/99 Error(E) General(G)
With due attention to F, of table (1% and 5%), it can be conclude that there is a great significant difference between treats and blocks at evaluate levels.
With due attention to significant effect of treats we tend to compare Means.
With due attention to conclude d' at (1% and 5%) level equal to 1/58 and 1/061, it got clear that results from pentrometer have significant difference with results of laboratory and pentrometer.
The soil of clay group:
Table 13: The evaluation of CBR amount in different methodds of soil of clay group. Treat control Penterometer Laboratory Repetition 1 4/5 6 5/45 2 3 4/5 2/84 3 3 3/45 2/68 Table 14: Variance analyzation of soil of clay group. Change resource ss df Ms=[s.sup.2] F Treat(T) 2/34 2 1/17 6 Black(R) 8/83 2 4/415 22/64 ** Error(E) 0/78 4 0/195 General(G) 11/95 8 -- Change resource [F.sub.5%] [F.sub.1%] Treat(T) 3/88 * 6/99 Black(R) 3/88 6/99 Error(E) General(G)
With due attention to Fs of the table, it can be conclude that between treats, there is just a significant difference at 5% level, but there is a great significant difference between blocks. With due attention to this fact that treats are significant, we tend to compare Means.
With due attention to d' calculated at (1% and 5%) level equal to 1/59 and 1/0728, it got clear that pentrometer results have significant difference with results of laboratory and control at 5% level.
Discussion and conclusion:
In general, silvan's bearing ability based on the type of soil group and humidity level is variable and as mentioned before, there are different methods to gain this ability, such as CBR evaluation in laboratory, evaluation with pentrometer device at area (studied area), with due attention to calculations in the form of the plan of completely random block and analyzes related to Means comparison through LSD-test and between obtained from CBR classification in USCS system and two methods in different soil group which was mentioned above.
Obtained results show that there is no significant difference between laboratory results and CBR classification in USCS system even at 99% assurance level. And laboratory results are always acceptable as certain results in CBR evaluation but results obtained from CBR evaluation with pentrometer compared with CBR evaluation in USCS and laboratory classification. In soil groups of 'sand and pebble' and macro tissue loomi. There was no significant different between evaluated CBR pentrometer and different methods, and results are acceptable. But in soil groups, micro tissue loomi and clay soil, there is significant difference between results. Since CBR evaluation with pentrometer is done in natural lands and through square method, is to some extent a function of environmental situation. So if the soil of land, naturally and condensively becomes dry(humidity be less than desired situation), and the root of trees and other variants sometimes do exist in the tissue of the soil. Then it can change the amount of CBR evaluation. During the study, such cases were observed, too. But with qualitative evaluation of CBR date. Although this difference was significant, data obtained from different methods were quantitively in specific range of classes. And it means that although obtained results from CBR evaluation in the method of using the pentrometer was different from other evaluations, with due attention to the range of CBR classification, is an acceptable method.
Received 11 September 2013
Received in revised form 2013
Accepted 25 November 2013
Available online 4 January 2014
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Muhammad Reza Azarnoush
Faculty of Forestry, Chaloos Branch, Islamic Azad University, Chaloos, Iran
Corresponding Author: Muhammad Reza Azarnoush, Faculty of Forestry, Chaloos Branch, Islamic Azad University, Chaloos, Iran
Table 1: Classification different groups of soil. The name of soil class (tissue) group Different type of soil 1 Sand and peeble Sand and peeble, loomi with sand and peeble, gravel with sand and peeble 2 Gravel Gravel, Loomi-gravel 3 Loomi with large tissue Gravel-Loomi, Loomi-silty and loomi with clay less than 187 4 Loomi with Silty-loomi with clay more than 18% and clay-loomi 5 Clay Clay-gravel, vlay silty and clay 6 Organic Such as different types of peat Tables 6: Comparision treats of penterometer, laboratory and control with LSD-test (p=1% and 5%). Treat Mean d control 45 [+ or -] 0 penterometer 48/8 3/8 ** laboratory 44/43 -0/57 (ns) * and ** are significant respectively at 1% and 5% of perecentage level -(ns) is not significant. Table 9: The comparision between Mean of penterometer treat and laboratory and control with LSD-test (p=1% and 5%). Treat Mean d control 25 [+ or -] 0 penterometer 27/25 +2/25 (ns) laboratory 24/01 -0/99 (ns) Table 12: Comparision between treats of penterometer and laboratory and control with LSD-test. Treat Mean d control 13/33 [+ or -] d penterometer 15/05 1/7 ** laboratory 13/6 0/27 (ns) Table 15: The evaluation of penterometer of treat and laboratory and control with LSD-test. Treat Mean d control 3/5 [+ or -] 0 penterometer 4/65 1/15 ** laboratory 3/66 0/16 (ns)
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|Author:||Azarnoush, Muhammad Reza|
|Publication:||Advances in Environmental Biology|
|Date:||Nov 1, 2013|
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