SY/T 10025-2009Pre-operation inspection for offshore drilling unit (English PDF)

1.0.5 The retaining structure for earthwork be well designed for connection with

bridge abutments, tunnel openings, catenary pillars, sound barrier foundations and other projects.

1.0.6 Retaining structure's design shall promote the use of safe and reliable new technologies, new structures, new materials and new processes.

1.0.7 In addition to meeting this code, the design of the retaining structure shall also comply with the relevant national standards.

2.1 Terms

2.1.1 Retaining structure

Structures which are used to support and strengthen the rock-soil body and maintain its stability.

2.1.2 Gravity retaining wall

A retaining structure that resists the earth pressure and prevents the soil from slumping by the weight of the wall. When there is a counterfort platform on the back of the wall, it is called a counterfort retaining wall.

2.1.4 Counterfort retaining wall

A retaining structure which is composed of standing arm plate, a toe plate, a heel plate, a buttress, etc., which resists the earth pressure by the gravity of the wall body and the soil body above the heel plate.

2.1.5 Groove retaining wall

A retaining structure of U-shaped which is composed of side walls and a baseplate, that withstands earth pressure, water pressure, buoyancy, meanwhile prevents surface water or groundwater from infiltrating.

2.2 Symbol

P0 - Track load;

Q - Train load;

q - Unit load;

��0 - Static earth pressure factor;

��a - Active earth pressure factor;

Ex - Horizontal earth pressure;

Ey - Vertical earth pressure;

3.1 General provisions

3.1.1 The setting of subgrade's retaining structure shall be determined in combination with topography, geology, land use, environmental conditions, etc.

The following sections should be equipped with retaining structures.

3.1.2 The section where the retaining structure is set up shall be identified with engineering geology, hydrogeological conditions, environmental conditions and physical and mechanical properties of rock-soil.

3.1.5 Subgrade's retaining structures located in soft soil, slopes and other

sections shall be checked for overall stability.

3.1.6 At certain intervals in the longitudinal direction of the retaining structure

and at the junction with other buildings, it shall provide expansion joints.

3.2 Design requirements

3.2.1 The design service life of the railway subgrade's retaining structure is 100 years. It shall meet the relevant provisions of the current "Code for durability design on concrete structure of railway" TB 10005.

4.1 General provisions

4.1.1 The load on the retaining structure of railway subgrade can be classified according to Table 4.1.1 according to the time of action and the frequency of occurrence. The train load used in the design shall comply with the provisions of the current "Code for design on subgrade of railway" TB 10001.

4.1.2 The design of the retaining structure shall adopt the corresponding load combination and safety factor according to the functional requirements of the structure and the design conditions.

4.1.3 When the retaining structure is designed by the total safety factor method, the load combination shall comply with the provisions of Table 4.1.3; when designed by the limit state method, the value of the partial factor in the load combination shall comply with the relevant requirements.

4.2 Main force

4.2.1 The action of earth pressure shall be determined based on the specific conditions of the subgrade's retaining structure, using active earth pressure, static earth pressure or passive earth pressure, combined with engineering experience, as multiplied by the corresponding earth pressure's correction factor. The passive earth pressure in front of the open-cut foundation's retaining wall can be disregarded.

4.2.4 The calculation of the action of water and soil below the normal water level of the soaking retaining structure shall meet the following requirements.

4.3 Additional force

4.3.1 The soaked retaining structure shall consider the penetration force under the following conditions.

4.4 Special force

4.4.1 The calculation of earthquake action shall comply with the provisions of the current "Code for seismic design of railway engineering" GB 50111.The static method can be used to calculate the seismic force on the rigid structure and the fractured prism of the soil.

4.4.2 The earth pressure on the wall back of the retaining structure shall include the horizontal seismic force. Gravity retaining structure or the non-gravity retaining structures with large self-weight shall consider the horizontal seismic forces on the structure.

4.4.3 In the case of flood level, the earth pressure on the wall back of the retaining structure shall consider of the flood action; but it shall not be considered at the same time as the seismic force.

5.1 General provisions

5.1.1 The concrete, steel bar, geosynthetic material, filler, stone and cement

mortar used in the retaining structure shall be determined according to the structure type, function, scope of application, application environment, etc.

5.2 Concrete, mortar rubble and cement mortar

5.2.1 Retaining structure may use reinforced concrete, plain concrete and flake concrete.

5.2.2 The concrete strength shall be determined according to the standard value of cube's compressive strength. The standard value of the compressive strength of the cube is a cube specimen with a side length of 150 mm which is made and cured according to the standard method, which is measured by the standard test method at 28d or the age specified in the design.

5.3 Steel

5.3.1 The steel bars, prestressed steel wires and steel strands used in the

retaining structure shall meet the following requirements.

5.4 Geosynthetics

5.5 Filler and geotechnical

5.5.1 When calculating the earth pressure behind the wall of the retaining

structure of the embankment section, the physical and mechanical indexes of the filler shall be determined according to the test data.

6.1 General provisions

6.1.1 The gravity retaining wall is suitable for general areas, soaking areas and earthquake areas. Gravity retaining wall may be installed on the shoulder, embankment and cutting.

6.1.2 The height of gravity retaining wall shall meet the following requirements.

6.1.3 The wall material should be concrete, rubble concrete, etc. The rubble stone content per unit volume of rubble concrete shall not exceed 20%.

6.1.4 The wall back type of gravity and counterbalanced retaining walls may be selected according to Figure 6.1.4.For the shoulder section, it may choose the counterbalanced retaining wall or a gravity retaining wall whose wall back is a broken line.

6.2 Design and calculation

6.2.1 The calculation of earth pressure acting on the gravity retaining wall shall meet the following requirements.

6.2.3 The buoyancy of the wall body shall comply with the provisions of clause

4.2.4 of this code.

6.2.4 The slide-resistance stability of the retaining wall shall be checked in accordance with clause 3.22 of this code. The total sliding force T and total slide resistance force R shall be calculated respectively according to formula (6.2.4-

6.3 Construction requirements

6.3.1 The base and foundation of the retaining wall shall meet the following requirements.

6.3.4 The longitudinal connection design of the retaining wall shall meet the following requirements.

6.3.5 Retaining walls shall be provided with inspection ladders at appropriate locations. Steps should be provided at both ends of the cutting's retaining wall.

7.1 General provisions

7.1.1 Cantilever and counterfort retaining wall are suitable for general areas, soaking areas and earthquake areas. Cantilever retaining wall's height should not be greater than 6 m, counterfort retaining wall's height should not be greater than 10 m.

7.1.2 Cantilever retaining wall and counterfort retaining wall shall adopt reinforced concrete structure, the form of which is as shown in Figure 7.1.2-1 and Figure 7.1.2-2.

7.2 Design and calculation

7.2.1 When the cantilever or counterfort retaining wall is installed on the shoulder, the lateral and vertical earth pressure on the structure caused by the track and train load may be calculated according to the elastic theory. The stress distribution is as shown in Figure 7.2.1.

7.3 Construction requirements

7.3.1 The width of the top of the cantilever retaining wall shall not be less than

0.2 m. When the height of the wall is greater than 4 m, it should set a chamfer on the inside of the standing arm plate. The width of the top of the counterfort retaining wall shall not be less than 0.3 m.

7.3.6 The thickness of the concrete protective layer shall comply with the provisions of the current "Code for durability design on concrete structure of railway" TB 10005.

7.3.7 When pouring concrete, the pouring shall be completed at one time. If there is a break, the new concrete and the poured concrete shall be firmly bonded. The tenon shall be poured at the same time as the concrete of the baseplate.

7.3.8 The filler shall be compacted in layers. The reverse filter layer shall be constructed in time during the filling process.

8.1 General provisions

8.1.1 Groove retaining wall is suitable for cuttings with high groundwater level and cuttings or embankment sections with restricted grading conditions. The common structural form is as shown in Figure 8.1.1.

8.1.2 The side wall's cantilever height should not be greater than 8 m; the top width should not be less than 0.3 m.

8.1.3 The design elevation of the side wall top of the groove retaining wall shall be 0.5 m higher than the design ground water level. It shall take water blocking measures in the sections of waterlogging and water accumulation.

8.2 Design and calculation

8.2.1 The groove retaining wall shall be subjected to stability check, structural design, water-proof and drainage design. The stability check shall include the anti-floating, anti-sliding, anti-overturning, compressive stress of the base, the deformation of the foundation.

8.3 Construction requirements

8.3.1 The constructional requirements of the reinforcing rate, steel bar overlap, anchoring length of the groove retaining wall and the uplift pile shall comply with the relevant provisions of the current "Code for design of concrete structures"

GB 50010.The requirements for uplift pile's construction shall also meet the following requirements.

8.3.2 For groove retaining wall, it may set the settlement joints, expansion joints at the interval of 15 m ~ 20 m. The joint width should be 20 mm ~ 30 mm.

Meanwhile it shall meet the requirements of clause 3.1.6 of this code.

8.3.3 For the groove retaining walls, it shall be provided with force transmission rods at the settlement joints and expansion joints, which shall meet the following requirements.

8.3.6 Reinforced concrete materials used for groove retaining walls shall comply with the provisions of clause 5 of this code.

8.3.7 The drain holes and reverse filter layers of embankment type groove

retaining walls shall comply with the provisions of clause 7 of this code.

9.1 General provisions

9.1.1 The reinforced soil wall is suitable for general areas and earthquake areas.

It can be set on the shoulder or embankment slope. The height of the single- stage wall should not be greater than 10 m.

9.2 Design and calculation

9.2.1 Reinforced soil wall shall be checked for internal and external stability; if necessary, it shall perform post-construction settlement check and horizontal deformation check, etc. The internal stability check shall include the tie-bar strength, uplift force check, wall panel structure design, etc.

9.2.3 The internal stability check shall meet the following requirements.

9.2.5 During external stability design, the anti-sliding and anti-overturning

stability check shall comply with the provisions of clause 6 of this code. The compressive stress of the base may be calculated according to formula (9.2.5).

9.3 Construction requirements

9.3.1 The structural design of the reinforcement material of the reinforced soil

wall shall meet the following requirements.

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