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Before the Construction period, we should make it the preparations of Organization, Goods and Materials and Technology.

The main content of Subgrade Technical Preparations:

1. be familiar with the Design Documents;
2. investigate and check the construction site;
3. delivery the technical disclosure and survey stake;

   Annotation 1

   Design unit delivers survey stakes to the construction unit. If some stakes are missing, the design unit shall fill the vacancies. After the construction unit has signed the confirmation, it finds that there are still some missing stakes, which shall be made up by the construction unit, and the cost and delay caused by it also will be indemnified by the same unit.

4. retest and layout survey;
5. pilot and execute the test construction;

The general criterion of Subgrade Construction Preparations:

1. Before the construction roadbed, on-site investigation and verification should be carried out, on the basis of comprehensively understanding of design requirements and design details.

2. After the detailed on-site investigation, the implementing construction organization design should be compiled according to the design requirements, contracts, on-site conditions and etc, and submitted for approval in accordance with the management regulations.

   Annotation 2

   The Chief Technology Officer in charge of the construction enterprise examines and approvals the “construction organization design”.

3. Before the construction roadbed, it’s necessary to establish and perfect the management system of quality, environmental protection and safety and the inspecting system of quality, and to train all kinds of the construction personnel on the job as well as to deliver the technical and safe disclosure.

   Annotation 3

   Human management in the on-site construction project (i.e. project management) mainly focus on three points:

   1. Certified Employment;
   2. Safety Training;
   3. Technical and Safe Disclosure

   Eg. What are the requirements for workers engaged in welding rebar?

   Answer:

   1. hold the Welding Technical Qualification Certificate
   2. have been taken a Safety Production Training
   3. finished the technical and safe disclosure

4. Temporary works should meet the needs of normal construction, and ensure the original function of existing roads, structures and farmland water conservancy facilities within the scope of influence of construction roadbed.

The Test:

1. Before the subgrade construction, laboratories shall be established in accordance with relevant regulations and requirements.
2. Before the subgrade construction, relevant tests should be carried out on subgrade base soil. At least two points are taken per kilometer. When the soil quality changes greatly, the sample points will be increased according to the specific conditions.
3. Materials intended to be used as embankment fillings with different sources and properties should be reviewed and sampled. Soil test items include natural moisture content, liquid limit, plastic limit, standard compaction test, CBR test, etc. Some pilot projects like particle analysis, relative density, organic matter content, soluble salt content, frost heave and swell crement test should be done when necessary.
4. When using special materials as fillers, corresponding tests will be carried out according to relevant standards, and the same to environmental impact assessment when necessary, which can be used only after approval.

   Annotation 4

   Special Materials: The special filler here generally refers to the fly ash, because fly ash is a light filler, the biggest problem is that it is easy to cause enviromental pollution, such as dust pollution.

The choice of test roadbed section:

The test roadbed section chosen should be representative in geological conditions, section form and other engineering characteristics, and the length of it should not lessen than 100m.

Annotation 5

Generally, what sections need to be tested are embankments.

Under the following cases, the construction of test roadbed section should be carried out:

1. highway embankment of grade II and above;
2. rock-fill embankment, earth-rock embankment;

   Annotation 6

   The distinguish between rock-fill embankment and earth-rock embankment lies in the amount of stone stocks in the fillers.

   Earthwork embankment: the proportion of stone stocks < 30%

   Earth-rock embankment: 30%< the proportion of stone stocks < 70%

   rock-fill embankment: 70% < the proportion of stone stocks

3. special section embankment;
4. special fillers embankment;
5. embankments intended to adopt the new technology, technique and materials.

The main content of test roadbed section construction:

1. the test reports of fillers;
2. the main parameters of compaction technological process:
   • the combination of machine equipment;
   • compaction machine specifications;
   • loose laying depth / loose laying thickness;

     Annotation 7:

     1️⃣ The ultimate result of loose laying depth depends on the test, not on the calculation, and the calculation is only an intermediate method.

     2️⃣ The number of loose laying depth varies with the materials:

     1. The loose laying depth of earthwork embankment is controlled at 30 cm;
     2. The loose laying depth of earth-rock embankment is controlled at 40 cm;
     3. The loose laying depth of rock-fill embankment is controlled at 50 cm.

     3️⃣ If the construction is carried out in winter, the thickness of loose laying should be reduced appropriately, and be generally controlled within 30cm.

   • the number of compaction times;
   • compaction velocity;
   • optimum moisture content;
   • allowable deviation of moisture content.
3. control method and index for process quality;

   Annotation 8: process quality

   Process quality refers to the sum of characteristics of process’s ability to meet the explicit and implicit needs.

4. the index and standard of quality evaluation;
5. optimized construction organization schema and process;
6. record and arrange primary records and process records of construction;

Site Clearance:

1. The original structures in the scope of land used for highways should be treated according to the design requirements.
2. For the highway embankments of grade II and above and the highway embankments with filling heights less than 1m, the tree trumps in the scope of the subgrade should be excavated and then the holes must be filled up and tamped, and for the highway embankments of below the grade II with filling heights higher than 1m, tree trumps could be retained but the roots can’t be exposed to the surface. The tree trumps in the scope of borrow pit should be fully excavated.
3. The surface humus soil, topsoil, sward of the original surface in the scope of road and borrow pit should be cleared, on the other hand, the filling section should be leveled and compacted according to the design requirements. The cleared surface soil should be fully utilized.

   The amount of site clearance generally is controlled within 30 cm.

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