What are the experimental projects to be done for sand and gravel cushion?

Sand and gravel cushion. After it is done, if the design has a degree of compaction.

If required, sand filling experiments should be done.

1. Raw material testing.

2. Then do the mix ratio, it should be noted that it is necessary to do a compaction test.

3. Finally, the degree of compaction is tested.

Experimental notes: 1) The elevation control pile should be properly protected during construction to prevent collision and displacement, and should be retested frequently.

2) The equipment pipelines protruding from the wall and various pipelines buried in the cushion should be properly protected to prevent collision or damage during construction.

3) In case of rain and snow during construction, temporary coverage should be done to prevent the cushion from being soaked or frozen.

4) After the cushion construction is completed, the next process construction should be carried out in time, otherwise, it should be enclosed and temporarily covered and often sprinkled with water.

5) The completed cushion shall not be stacked with heavy objects and driving vehicles.

The underlayment does not require any experimentation. When you make the cushion, the on-site supervisor can check whether the thickness of the cushion meets the requirements.

Under normal circumstances, the grading of sand and gravel cushion should first test the raw material and do screening, mud content and mud content. Then, the maximum dry density and the best water content of the sand and gravel should be determined by the vibration compaction method. After the construction is completed, the cushion is compacted, and the irrigation method or sand filling method is generally used.

Graded sand refers to the particle size (particle size) of sand or gravel mixed in a certain proportion and used for foundation or other purposes, and its ratio is different according to the specific engineering design. If the design is not specified, you may refer to the quota. Natural gradation refers to even sand and gravel.

If it is a sand cushion, the dry density of the cushion should be checked, and the dry density can be tested by the ring knife method or by small hammer penetration. For details, please refer to the description of the provisions of the GB50209-2010 and the following provisions of the construction quality acceptance code for building ground engineering.

If it is a replacement foundation, it should be tested with reference to the requirements of JGJ79 of the "Technical Code for Building Foundation Treatment", mainly two items: 1. Compaction coefficient 2, bearing capacity.

1. Before construction, sample the sand and gravel to the laboratory for the maximum dry density test, also known as the compaction test.

2. After paving and rolling, the compaction test is carried out, and the next layer of construction is carried out after meeting the design requirements, and the design elevation is carried out one by one.

3. In the data, there are experimental reports, backfill construction records, sand and gravel cushion quality inspection records, backfill concealment engineering acceptance records, etc.

1. The sand and gravel cushion needs to be compacted test report, etc.

Hello dear! Glad for your question! And the letter briefly describes the applicability and construction characteristics of sand and gravel cushion:

1. The materials used are different, and the ash soil is 3:7 (lime: soil).

The gravel cushion is divided into artificial graded sand and gravel cushion and natural graded sand and gravel cushion. The artificial graded sand and gravel cushion is to mix gravel and medium coarse sand evenly according to the gradation, and then pave and compact. The natural graded sand and gravel cushion is the naturally formed sand and gravel, which is directly used for cushion construction if the witness sampling is qualified.

2. The scope of application is different, and Panax notoginseng ash soil is suitable for treating weak soil layers with a thickness of 1 4m. The foundation has a certain strength, water stability and impermeability. Sand and gravel foundation is suitable for dealing with weak cohesive soil foundation with strong permeability, but it is not suitable for collapsible loess foundation and impermeable clay soil foundation, so as to avoid water accumulation and cause foundation subsidence and reduce bearing capacity.

3. Although the cost of the three foundations is very low, the ash cushion is slightly higher, the gravel cushion is lower, and the natural graded sand and gravel cushion is lower.

What is the application of sand and gravel cushion? What are the key points of construction? How is quality control carried out?

According to the situation you described, the gravel cushion is mainly used to enhance the strength of the pavement structure, and take into account the lack of drainage function of the pavement structure. Sand and gravel cushion is suitable for silt silt, collapsible yellow stone, plain filler, miscellaneous filler foundation and uneven grave and culvert, dark pond and other shallow treatment, is a direct replacement of the foundation in the weak treatment method of the concrete cushion is to make its surface smooth and convenient to tie steel bars on it, but also play a role in protecting the defeat of the foundation, are plain concrete, no need to add reinforcement, is the middle layer of the steel concrete foundation gas foundation The thickness of the gravel cushion and the broken brick cushion should not be less than 100mm. Description:

This article proposes a limit for the minimum thickness of the cushion in order to be consistent with the Code for the Design of Building Ground GB50037. 2. The cushion should be compacted (tamped) in layers to achieve a solid and smooth surface. Description:

This article puts forward the quality requirements during the construction process and after tamping to ensure the quality of construction. 3. The strength of the gravel should be uniform, and the maximum particle size should not be greater than the thickness of the cushion.

1. The thickness of the sand cushion should not be less than 60mm; The thickness of the sand and gravel cushion should not be less than 100mm.

Note: This article stipulates the limit of the minimum thickness of sand cushion and sand and gravel cushion in order to be consistent with the Code for Building Ground Design GB50037.

2. Natural graded materials should be used for sand and gravel. There should be no separation of coarse and fine particles when laying, and the pressure (ramming) is not loosened until the cover is not loosened.

Note: This article proposes quality control during construction. Master project.

3. Sand and gravel should not contain organic impurities such as grass roots; The sand should be medium sand; The maximum particle size of the stone shall not be greater than 2 3 of the thickness of the cushion.

Note: This article stipulates the material of the cushion to be Qingchong sum inspection method.

4. The dry density (or penetration) of the sand cushion and the sand and gravel cushion should meet the design requirements.

Note: This article stipulates that the dry density and test method of the cushion must be checked, and the dry density can be determined by the ring knife method or the small hammer penetration determination. General items.

5. There should be no quality defects such as sand nests and stone piles on the surface.

Note: This article proposes to inspect the quality defects and inspection methods of the cushion surface.

6. The allowable deviation of the surface of the sand cushion and the sand and gravel cushion shall be in accordance with the provisions of this specification table.

Note: This article proposes the allowable deviation value of the surface quality of the cushion and the corresponding test method.