This particular assignment has the sole purpose of focusing upon the various attributes and engineering designs pertaining to the different types of soils within the industry that deal with the aspect of construction. The term soil grading refers to the proper classification of the particle’s size distribution pertaining to any type of soil. There exist various sizes of the sieves which get utilized for the purpose of classifying the soil in question. These are uniformly graded soils, poorly graded, and well graded ones in this regard. The coarse-grained soils that are primarily sands or gravels get graded either as poorly graded or well graded for that matter. The term called liquid limit pertains to the content of moisture at which the fine-grained soil does not flow in the form of a liquid. Moreover, the term plastic limit refers to the content of moisture at which the fine-grained soil cannot be remodelled except for cracking. The platform of software known as “MS-Excel” has been taken into account for the sole purpose of performing the necessary calculations on the whole.
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Behaviour of the soil upon being subjected to external loads depends solely on its constituent particles’ size along with its arrangement. It becomes extremely crucial therefore to thoroughly study the shape, size, and gradation of those particles on the whole. The specific purpose of the classification of soil is nothing but to properly arrange the different soil types into the groups in respect of their properties of engineering. The very individual solid particle within a soil tends to have various sizes in this regard (Cami et al. 2020). This particular characteristic of the soil can have a significant effect upon its “engineering” properties. The size of such particles which constitute the soil might vary from the boulders to that of very large molecules. The particles of soils that are coarser than “0.075 mm” essentially make up the “coarse” fraction of the soils. This coarse fraction of the soil fundamentally consists of nothing but sand and gravel respectively. Clay and Silt are the very fine fractions pertaining to the soils.
Soil Grading
(i) Curve to plot the particle size distribution for soil
Figure 1: Plot to display the size distribution of particles for the soil
The above-displayed graph has been obtained upon the rendered data, by taking assistance from the software platform by the name “MS-Excel” in particular.
This particle size distribution curve is predicated upon the data which has undergone conversion from the unit of “mm.” to “micrometer (μm) on the whole. The percentage finer has been thoroughly calculated for each of the sieves in general. The term percentage finer refers to nothing but the “cumulative” mass that has been retained, divided by the “total” mass pertaining to the sample multiplied by the amount 100.
Percentage Finer = (Retained cumulative mass / Total mass) x 100
In the above plot, the term called percentage finer has been taken up along the “y-axis” and the size of the sieve along the “x-axis” on the whole. This particular curve is the very bedrock from which the required parameters can be calculated effectively (Crisp et al. 2021). These parameters are effective size, the coefficient of uniformity, and the soil’s curvature coefficient respectively.
(ii) Curve Inspection
Effective Size
The Effective Size (D10) pertains to the size of the sieve at which the nearly “10%” of the concerned particles are finer. In respect to the present scenario, D1O is near about 3.35 μm.
The very shape of the particles also assists in properly determining the underlying property of that soil (Egbueri et al. 2021). This particular shape of such particles essentially varies from the angular to the ones that are well round. The angular ones are generally discovered near rock which acts as their foundation. These particles generally have greater amounts of shear strength rather than the ones which are rounded in nature (Forte et al. 2019). The sole reason for the aforementioned fact is that it becomes extremely difficult for making them properly slide over the other for that matter. The particles are classified into the three following particle types based on the ratio of the width, length, and thickness respectively. These are as follows:
Flaky Particles
These kinds of particles are also known by the name plate-like particles. Such particles are more present mostly within the cohesive soils and are very thin in comparison to their breadth and length respectively.
Bulky Particles
The particles get termed as bulky when the width, length as well as the thickness are of equal order of the magnitude on the whole (Green et al. 2020). The soils which are cohesion less get referred to as bulky particles. Bulky particles get further classified as elongated needle-like particles and plate-like flaky particles respectively.
Elongated Particles
The elongated particles of soil are nothing but like “hollow” rods. It refers to a very special particle type which is present within the clay minerals, such as asbestos, peat, etc.
Coefficient of Uniformity refers to that ratio belonging to the size of the sieve at which “60%” of particles are very finer to the size of sieve at which “10%” particles are also very finer.
Cu = D60/D10
In this section, the value of D60 is near about “20 μm”
So, the value of Cu turns out to be near about “6” in this regard.
Coefficient of Curvature
The term Coefficient of curvature is nothing but the total measure of that degree of the curvature of the size distribution curve of the particles.
Cc = {(D30) ^2/ (D10 x D60)
Here, the value of D30 is near about “6.3” μm.
So, the value of the term Cc becomes near about “1.7” after putting the obtained value of D30 in this case.
The values of Cc and Cu are the most important factors for the purpose of properly classifying the soil in question. So, in this case the soil has been classified as “poorly” graded in particular (Hussein et al. 2019). The term poorly graded refers to the size distribution curve of particles that is relatively flat in nature and does not contain a very well-defined and demarcated peak on the whole.
Liquid and the Plastic Limit of the soil
In this section, the objective is to determine both the plastic limit as well as liquid limit of the concerned soil from the provided data. Moreover, the liquid limit (LL) of this soil can very well be determined by utilizing the “empirical” correlation existing between the “cone” penetrations along with the “moisture” content (%) in general (Kalkan et al. 2019). This particular test is known by the name “casagrande’s liquid-limit test” in essence.
Figure 2: Plot to showcase the liquid and plastic limit of soil
The respective plot has been obtained in “MS-Excel” from all of the provided data on the whole.
Liquid Limit Test of Soil
In the above-attached graph, the moisture content gets easily determined at that point the “cone-penetration” is “20” mm in particular. This point is nothing but where the “best-fit” line properly intersects the value of penetration, that is “20” mm. The aforementioned value represents the soil’s liquid limit for that matter (Kim et al. 2019). Furthermore, the graph renders clear insights for fetching the liquid limit of this soil and this limit has turned out to be “34.5%” in this case.
Plasticity Index of the Soil
The index of plasticity has been determined from the performed test and the value is “15%” in particular. The utilization of the formula takes place in this context to get the plasticity index (PI).
PI = LL-PL
In the above-mentioned equation, the term PL defines the Plastic Limit. As PL is “15%” so, the outcome of this equation turns out to be,
PI = (34.5% - 15%) = 19.5%
So, the value of the Plasticity Index is “19.5%” by dint of the above-showcased formula. Furthermore, based upon this value of plasticity index, the soil in question can very well be classified as the “Clayey” soil having low plasticity.
Consistency
The term consistency is utilized for describing the “physical” state of the soil in question. It is the “degree” of coherence which exists between the soil particles at any provided water content. This factor is directly linked to the water content present in soil (L Heureux et al. 2019). But it has also been discovered that various soils might contain various consistency even at the “same” water content.
Plasticity
It is nothing but the underlying ability of the soil to alter its shape upon the application of the load along with retaining its new shapes after the removal of that quantity of load. The fine particles of the sil such as clays essentially exhibit “plastic” behaviour.
Atterberg Limits
The Atterberg limit gets utilized as a guide which indicates the amount of soil required to consolidate or settle under load. The Atterberg limit is of three separate types and those are as follows:
(i) Liquid Limit
The “water” content that essentially marks the underlying boundary of plastic and liquid states of soil gets termed as the liquid limit. The soil’s liquid limit gets defined as the minimum content of water at which the specified “small” distributing force gets required for the soil to properly flow. In this content of water, soil has a very small amount of the shear strength.
(ii) Shrinkage Limit
The content of the water that marks the underlying boundary of solid state and semi-solid state pertaining to the soil gets known as the shrinkage limit. It is also defined as the “maximum” content of moisture below which soil ceases to come down in volume upon further drying.
(iii) Plastic Limit
Water content that properly marks the “boundary” of semi-solid state and plastic state of soil is known as the plastic limit (Lemenkov et al. 2021). Moreover, it is the minimum content of the water at which the soil can easily be rolled into the thread of “3 mm.” without cracking. In this “water” content, soil can be “deformed” plastically.
Scenario Question
(a) Here, the objective is to determine the “economical roller” as well as the design thickness pertaining to a “Type 1” capping layer. The fruitful determination of the aforementioned task takes place with reference to the design manual pertaining to the bridges and roads. In view of the manual in question, the “Type 1” capping layer gets utilized for such roads having a low to medium size of traffic along with “2o years of design life. The concerned thickness for this particular layer lies between “150 mm” and “350 mm” on the whole. One of the most important factors in this regard is the economical aspect (Rollins et al. 2021). The traffic load as well as the underlying conditions of the soil are taken into consideration for choosing the most “economical” thickness. The concerned manual essentially recommends a “capping-layer” thickness of about “300 mm” for the entire design life of “20” years. This in turn is predicated upon the assumption of the typical conditions of the soil and the “traffic-load” of near about “10 million” standard axles for that matter.
(b) In this particular section, suitable rollers are selected for the completion of this task. Moreover, the parameters such as the needed compaction width and rolling width are taken into consideration in general for performing the aforementioned task. In respect of the provided information, the value of rolling width is “3.25m” and the length of the road is “1500m”. This in turn renders a “total” area of “4875m²” in particular (Shi et al. 2021). The “capping-layer thickness” has been assumed to be “300mm” and this renders a “total” volume as mentioned in the section below:
Volume = Area x Thickness
Volume = 4875m² x 0.3m
Volume = 1462.5m³
The concerned manual essentially refers to the fact of utilizing a roller with vibration along with the mass of a minimum of “10” tons. The aforementioned gets followed for the sole objective of achieving the necessary effort of compaction. In relation to the concerned brochure, the two rollers for the task are “Bomag BW 138 AD-5”, and the “Caterpillar CB10” respectively. The latter has a total operating weight to the tune of “11.5” tons as well as the “drum width’ of about 1676 mm (Shivashankar et al. 2020). The former contains a total “operating weight” of about “4.9” tons along with the “drum width” of near about 1380mm. It is assumed in this context, that the rollers mentioned above can obtain a “compaction efficiency” of about 85%. So, the total quantity of the passes needed for obtaining the needed effort of compaction is calculated in the following section:
Compacted Volume = Volume x Efficiency of Compaction
Compacted Volume = 1462.5m³ x 0.85
Compacted Volume = 1243.1 m³
The total number of passes = Compacted Volume / (Mass of the Roller x Width of the Roller x Passes per meter)
Total number of passes for the Caterpillar CB10 = 1243.1m³ / (11.5 tons x 1676 mm. x 3, 25 meter) = 4.4 passes
The obtained value for the above-mentioned roller is rounded up to a total amount of 5 passes.
In the above manner the total quantity of passes for the roller “Bomag BW 138 AD-5” is calculated to be = 1243.1 m³ / (4.9 tons x 1380 mm. x 3.25 meter) = 12.5 passes
The values obtained for the above-showcased roller has been rounded up to a total value of 13 passes for that matter. Therefore, for the proper completion of this task, it is highly recommended to utilize both of the mentioned rollers on the whole. The necessary compaction effort gets achieved as the “Caterpillar CB10” makes the very initial passes and the “Bomag BW 138 AD-5” makes the very concluding passes in this regard.
Conclusion
There exist three primary factors which refer to the soil’s grading characteristics on the whole. The platform of software known by the name of “MS-Excel” has been utilized to properly perform the aspect of calculations. The mentioned factors are the curvature coefficient, uniformity coefficient, and effective size respectively. These, in totality represent nothing but the geometric attributes of the grading curve which essentially describes the type of any soil in particular. This software platform is also utilized to plot the graph that has displayed the soil particles’ size distribution along with the plastic and liquid limit of the soil respectively. The grade-size curve of distribution has been analysed thoroughly by utilizing the different sizes of particles such as D60, D10, and D30 respectively. This specific curve is nothing but the plotted graph between the percentage-finer along the y-axis in relation to the size of the concerned particle along the x-axis. The difference between the values plotted along these two axes is that, in the case of the x-axis, its values have been changed to the logarithmic scale for that matter. When the value of Cu extends greater than 4 to 6, then that soil gets classified as a one which is well-graded. But when this value drops below the mark 4, then that soil gets classified as a uniformly graded or poorly graded one in this regard.
References
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