Soil sieving analysis

Friday June-06 2025  17:13:27

What is soil sieving analysis

Soil sieve analysis is a soil particle size determination method based on the principle of mechanical separation. It is mainly used to analyze the content and distribution of coarse particles (usually larger than 0.075 mm or 0.063 mm) in the soil. By classifying soil samples through sieves with different apertures, the proportion of sand (0.05–2 mm), silt (0.002–0.05 mm) and clay (<0.002 mm) is determined to reveal the soil texture and structural characteristics.

Its core feature is to use a series of standard sieves with gradually decreasing apertures to separate and retain soil particles of different sizes on the sieve surface through vibration, thereby achieving classification according to particle size.

What is the purpose of soil sieving analysis?

Soil sieving analysis is a commonly used soil particle size analysis method, which is mainly used to determine the content of particles larger than a certain particle size (usually 0.063 mm or 0.075 mm) in the soil. Based on the principle of mechanical separation of particle size. The particles in the soil sample are classified according to their size through a series of standard sieves with gradually decreasing apertures. When the particle size is smaller than the sieve hole, they will pass through the sieve hole; when the particle size is larger than the sieve hole, they will be retained on the sieve surface.

① Understand the composition of soil particles: Soil is composed of particles of different sizes, such as sand, silt, clay, etc. Sieving analysis can determine the relative content of these different particle size components.

②Determine the soil particle size distribution: Understand the content of sand (0.05–2 mm), silt (0.002–0.05 mm) and clay (<0.002 mm) in the soil.

③Evaluate soil properties: Particle composition directly affects the physical properties of the soil, such as water permeability, water retention, aeration, fertility, etc., which in turn affects the engineering properties and agricultural production performance of the soil.

Texture category	sand (1~0.05mm)	silt (0.05~0.002mm)	clay (<0.002mm)
Sand	>80%	<10%	<10%
Loam	40%~80%	30%~45%	10%~30%
Clay	<40%	<40%	>30%

What is the method of soil sieving analysis?

Soil sieving analysis is divided into dry sieving method and wet sieving method. Choose the appropriate method according to the soil type and analysis requirements.

① Dry sieving method: suitable for soils with low water content and weak viscosity (such as sandy soil).

Collect soil samples, air dry or oven dry (usually at 105℃), and remove organic matter, roots and impurities. Weigh a certain mass of dry soil sample (usually 100-500g). Place the soil sample on a standard sieve group (arranged in order from large to small apertures, such as 2mm, 1mm, 0.5mm, 0.25mm, 0.1mm, etc.). Sieve by manual or mechanical vibration, usually for 5-10 minutes. Weigh the mass of soil remaining on each sieve separately and calculate the percentage of each particle size range. According to the sieving results, draw a particle size distribution curve or calculate the proportion of each particle size.

② Wet sieving method: suitable for soils with more clay or silt, because dry sieving may cause particle agglomeration.

Soak the soil sample in water and add a dispersant (such as sodium hexametaphosphate) to disperse the clay particles. Rinse the soil sample through the sieve with water flow to separate larger particles (such as sand particles). For fine particles (silt and clay) that pass through the smallest sieve holes, they are usually further analyzed in combination with sedimentation methods (such as hydrometer method or pipette method). The particles on each sieve are dried and weighed to calculate the ratio of each particle size.

What are soil sieves used for?

Soil sieves are widely used in various fields, and their core use is to separate and classify soil according to particle size. In agricultural production, soil sieves are used to analyze soil texture, which directly affects the permeability, aeration and fertilizer retention capacity of crops, and helps farmers choose appropriate planting methods and fertilization strategies. For example, by screening to understand the ratio of sand, silt and clay in the soil, it can be determined whether the soil is sandy, loam or clay, and thus determine whether the soil needs to be improved.

In addition, in the field of civil engineering, soil sieves can be used to analyze the particle size of roadbeds, foundations and fillers, evaluate their bearing capacity, permeability and compaction, and ensure the stability and safety of engineering structures such as roads, buildings and dams. For example, when building a highway, the roadbed materials will be strictly screened to meet the grading requirements of the design and avoid later settlement or deformation.

Soil sieving analysis test procedure

Sample preparation: Spread the air-dried soil sample flat on a clean wooden board and crush it with a pestle with a rubber head (to avoid damaging the soil particles). Pass the 2mm sieve, grind the soil sample on the sieve and pour it back into the 2mm sieve, and use the soil sample under the sieve as the sample to be tested. Weigh the mass of the soil sample on the sieve (m₁), calculate its percentage of the total soil sample, and use it as the coarse particle content.

Sieving analysis

① Coarse sieving analysis (>0.075mm particles): Weigh the soil sample that passes the 2mm sieve (m₂), pour it into the top sieve (2mm sieve) of the sieve group stacked from top to bottom according to the aperture size (such as 2mm, 1mm, 0.5mm, 0.25mm, 0.10mm, 0.05mm sieve), place it on a vibrating sieve machine for 10 minutes, and then sieve it one by one on a clean shallow plate according to the sieve sequence, starting from the sieve with the largest aperture, until the sieve out per minute does not exceed 1% of the total sample. The particles that pass through are added to the next sieve and sieved together with the sample in the next sieve, in order, until all the sieves are sieved. Weigh the mass of the sample on each sieve to an accuracy of 0.1g. The sum of the sieve residue of each sieve and the remaining amount in the bottom plate and the total amount of the sample before sieving shall not differ by more than 1%.

② Fine sieve analysis (<0.075mm particles): If it is necessary to determine the composition of particles smaller than 0.075mm, the sieve residue of each sieve after sieving and the remaining soil sample in the bottom plate can be combined, further ground with a mortar, and then the fine particle content can be determined by sedimentation method (such as hydrometer method) or laser particle size analyzer.

Result calculation: With the cumulative content of soil particles smaller than a certain particle size as the ordinate and the particle size as the abscissa, draw a particle size distribution curve on semi-logarithmic coordinate paper, and find out the percentage of soil particles smaller than a certain particle size in the total mass according to the curve to determine the soil particle composition.

Precautions for soil sieving analysis

The soil sample must be fully air-dried, and the wet soil sample must be dried before being crushed to avoid particle adhesion affecting the screening results. Avoid excessive force to damage the soil particles during the screening process, especially for soils with strong structure.

The screening time of the vibrating screen can be adjusted according to the properties of the soil sample, and the screening time of clay soil needs to be appropriately extended. When analyzing fine particles, if the soil sample contains organic matter or calcium carbonate, it must be pretreated first (such as removing organic matter with hydrogen peroxide and removing calcium carbonate with hydrochloric acid).

In short, soil sieving analysis is an indispensable first step in understanding the physical properties of soil and conducting engineering classification. It is a classic and important method for determining the physical properties of soil. Through standardized operation and accurate data processing, it can provide reliable particle size information for soil science, engineering practice and environmental management.