How many groups of sand and gravel mattress sampling, how to sample gravel

Sand and gravel mattress is the treatment of sand and gravel cushion foundation. Sand and gravel mattress sampling: At least 3 groups were taken per unit.

The specific requirements for sampling shall be implemented in accordance with the requirements of the Code for Acceptance of Construction Quality of Building Foundation Engineering GB 50202-2002

For gray soil foundations, sand and gravel foundations, geosynthetics foundations, fly ash foundations, strong compaction foundations, grouting foundations, and pre-compacted foundations, the results (foundation strength or bearing capacity) after completion must meet the standards required by the design. The number of inspections should not be less than 3 groups per unit of project.

The sand and gravel mattress you said is the sand and gravel cushion foundation treatment, and the specific requirements are implemented in accordance with the requirements of the "Code for Acceptance of Construction Quality of Building Foundation Engineering" GB 50202-2002 (the article is a strong article):

For gray soil foundations, sand and gravel foundations, geosynthetics foundations, fly ash foundations, strong compaction foundations, grouting foundations, and pre-compacted foundations, the results (foundation strength or bearing capacity) after completion must meet the standards required by the design. The number of inspections should not be less than 3 points per unit of project, at least 1 point per 100m2 for projects above 1000m2, and at least 1 point for every 300 m2 for projects above 300m2. There should be at least 1 point under each independent foundation, and 1 point for every 20 linear meters of foundation groove.

When sampling from the stockpile, the sampling sites should be evenly distributed. Before sampling, the surface layer of the sampling site should be removed, and then 8 parts of sand and 16 parts of stones with roughly equal sample amounts should be taken from each part to form a group of samples.

When sampling, if the pile is cone-shaped, the stone pile can be divided into three layers, the lower layer is the bottom, not too close to the ground, because the large particle size stone always has to slide down to the bottom of the periphery when the stone is discharged, and the sampling point is arranged too much will cause the stone sample to be large and not representative.

Therefore, the stone can be evenly distributed along the circumference at the bottom of the 6 sampling parts, 3 points of the abrasive cloth; The middle part of the pile is the middle layer, and 8-9 sampling parts are evenly arranged along the circumference, and 4 points of the abrasive cloth; The top of the pile is the top of the upper layer of the shovel, and the top of the pile is arranged with 1-2 sampling parts, and the arrangement of the sampling parts (more than 16 points for stones and more than 8 points for sand) can truly represent the actual condition of the sample.

If the stones or sand are piled up in a flat form, no less than 16 or 8 sampling sites can be evenly arranged, and the sampling volume of each part should be basically equal.

Fractionation of the sample.

Reduction of sand: The sample is placed on a plate, mixed evenly in a wet state, and stacked into a "round cake" shape with a thickness of about 20mm, and then the "round cake" is divided into roughly equal parts along the two diameters perpendicular to each other, and the two parts opposite the diagonal are mixed again, and then piled into a "round cake" shape. Repeat the process until the number of samples is reduced to the amount required for the test item.

Fractionation of stones: The sample is placed on a plate, mixed evenly in a natural state, and formed into a cone, and then the cone is divided into roughly equal parts along the two diameters perpendicular to each other, and the two parts diagonally are remixed evenly, and then stacked into a cone. Repeat the process until the sample is reduced to the amount required for the test.

Under normal circumstances, the sample amount should be more than 4 times the amount required for the test, that is to say, at least 2 times of reduction should be carried out to obtain the test amount, and not one time of reduction to get the required amount, so the sample is not representative.

Each shift is sampled to inspect the particle size gradation, clay and other impurity content, and coarse particles greater than 1.

The unevenness coefficient cu of graded gravel particles is not less than 02mm and less than 3, and the mass percentage of coarse particles on the crushed surface is not less than 30 and is greater than 22 4mm, and does not contain impurities such as clay.

In the process of graded gravel production, the construction unit checks the particle size gradation, the content of impurities such as clay, and the coarse particle content of the crushing surface greater than 22 4mm once per shift. The particle size, gradation and quality of the graded gravel filler in the transition section of the roadbed should meet the design requirements. The content of needle-like and flake gravel is less than 20.

The content of soft and fragile stone shall not exceed 10.

1. The wear rate of particles with a particle size greater than 1 7mm should not exceed 30, and the immersion loss rate of sodium sulfate solution should not exceed 6; The liquid limit of fine particles less than 0 5mm should not be greater than 25, and the plasticity index should be less than 6.

2. Graded aggregate can be used as asphalt pavement and cement concrete pavement base and subbase, and can also be used as an improvement layer of roadbed. Under the premise of good drainage, graded aggregates can be used for roads with different traffic levels in different climate zones. The use of graded aggregates is particularly advantageous in humid and rainy areas.

3. According to the "double standard" construction site hardening of the Provincial Department of Transportation and other mixing site construction, the position of various raw materials is reasonable, and the material wall is between the piles to prevent mixing between the materials.

Sampling with sand irrigation:

It is to dig a hole in the ground to get the sand and gravel inside, and the sand and gravel to be brought back to the laboratory for testing, fill the standard sand in the sand filling cylinder, weigh it to see how many grams there are, put the standard sand into the hole to let it fill the hole naturally, and finally weigh the remaining sand in the sand filling cylinder to finish.

Sand JGJ52-2006 with the same origin, the same specifications, every 400m3 or 600t for a batch, less than this number is also counted as a batch. After removing the surface layer on the sand pile, take roughly the same amount of samples in 8 different parts, mix well, and then extract them according to the four-point method Sampling quantity: 15kg Routine inspection items include:

fineness modulus, particle gradation, apparent density, bulk density, mud content, mud content; Alkaline activity, sulfur trioxide, mica content, organic matter and robustness are optional test items; Sea sand must be tested for chloride content.

Shizi JGJ52-2006 with the same origin, the same specification, every 400m3 or 600t for a batch, less than this number is also counted as a batch. After removing the surface layer on the stone pile, roughly the same amount of samples was taken in 16 different parts, mixed well, and then extracted according to the quartering method Routine inspection: the maximum particle size is 25mm:

20kg；Maximum particle size 25mm: 40kg.

Crushing index: 10 20mm particles 15kg Routine inspection items include: particle gradation, needle flake content, mud content, mud content; Alkaline activity, sulfur trioxide, organic matter and robustness are optional test items.

The crush index test must specify the type of rock (hydrogenic rock, metamorphic rock, or igneous rock).

There is a point every 100 square meters, and each point of each layer is buried with yellow sand and the same thickness as each layer of gravel. After rolling, take the middle and lower part of each point. It refers to the backfill of sand and gravel under the foundation of the residential building, and it is best to take the axis or the bottom of the beam.