Excavation refers to any excavation and excavation at a level below ground level or at a level below the adjacent building. In most construction projects, enforcement activities begin with excavation / excavation operations on site. This part of the execution operation, which often accounts for a small portion of the project’s physical progress, is undoubtedly one of the most important stages of the project implementation.
The importance of the project phase is not solely due to the technical complexity. When digging, there are always reasonable concerns for adjacent buildings and ensuring that they are safe from danger.
Good Stabilization Techniques
1. Control method:
In this method, special measures are taken to control soil drift from the soil wall of the excavated area. In this method, it is necessary to use the soil adjacent to the pit wall. Therefore, this method cannot be used or restricted in cases where the soil adjacent to the ditch is under a building or in the neighborhood or in the area of urban installations and passages.
2- Sewing Back Method:
In this method, since the injection of concrete is used, it prevents very good soil movement and landslide, and in addition prevents soil in the walled area to inhibit the movement of the ground, thereby reducing the landslides. is. The use of this method is restricted to the use of the soil in the area where the excavated area is adjacent to a building.
3- Diaphragm wall method:
This method is also widely used beneath the earth’s dams and urban facilities such as the metro and prevents any leakage. The use of this technique in urban areas also has limitations such as the use of horizontal bracing and oblique traction elements.
4- Method of mutual control:
This method is suitable for low width cavities by digging wells on both sides of the cavity and placing metal profiles on them and connecting the opposite profiles to either beams or trusses. This method is often used for special low widths in channel execution operations.
5- Method of candle execution:
In this way, we run candles around the land to be plowed at certain intervals. These candles can be of different types of structural materials such as steel, concrete and wood. Concrete piles can also be pre-made or in-situ. In many urban projects, pre-made piles cannot be used due to the problems of pile shedding and only the piles can be run in situ.
6. Sanding method:
In this way, we first hit the shields on the sides of the pit and then start digging. Once the excavator has reached sufficient length, we install the horizontal beams on the shields and on them. We then attach the vertical pressure brackets to these horizontal struts perpendicular to the shield plate. This method is very suitable for running channels, especially for long lengths, as well as for short widths.
7. Trussing method:
Trenching is one of the most convenient, economical, and most common methods of guard construction in urban areas. Its execution is simple and does not require high equipment and expertise, yet it is very flexible in terms of performance in different situations.
Dismantling guard structures:
The guard structure can be dismantled when a part of the structure is being constructed that can withstand landslides. These structures can be the retaining wall of the structure or all or part of the building frame. If all or part of the building is to be replaced, the guard structure should be taken into consideration when designing the building and designing the frame for the loads.
Before excavation begins:
- Before the demolition of the building, the project examined how the adjacent buildings were connected to the building, and the boundary walls, the location and the way in which the boundary walls were connected, the beams or roofs of the two adjacent buildings, the openings and the front door. Chimneys and pipes or ducts located on the boundary walls, type of materials, burnout and presence of cracks in the adjacent building wall shall be identified.
- By constructing secure roofs using metal scaffolds covered with appropriate mesh, it provides adequate protection against possible collapse of roofs, walls, yards and passages adjacent to the site prior to demolition. .
- Prior to demolition at the project site, it identified the sewage wells and filled them with appropriate materials. If the depth of these wells is more than the depth of the digging site, these wells should be filled with low-grade concrete or submerged concrete, at least 50 cm above the level of the digging floor, and then filled with other suitable materials to the ground level. The location of these wells should be delineated in the final drawings of the guard structure and considered as part of the requirements in the design of the digging safety conditions.
- The demolition method must be carefully selected and the demolition operation of the project site building supervised by the supervising engineer. Care must be taken in the selection of demolition tools and equipment so as not to enter vertical or lateral dynamic and static forces during demolition. It is particularly important to demolish and remove walls adjacent to adjacent buildings by non-impact methods and tools.
- Prior to demolishing the site, it is necessary to disconnect the electrical and mechanical installations in the facility by obtaining the approval of the relevant authorities and with the supervision of the relevant technical expert.
- The technical factors responsible for the project, especially the supervisor and the supervising engineer, are fully justified by the various stages of digging and how the prefabricated elements are constructed and the coordination between the executing engineer, the supervisor and the design engineer to deal with anticipated and unforeseen issues. Come on.
- Adequate warnings about the dangers of demolition were given to the residents of adjacent buildings, and they provided the necessary measures to prevent them from settling in the immediate vicinity of the excavation boundary. He even predicted another place for the inhabitants of the adjacent buildings and vacated it. Also, dump valuable or heavy equipment or move it to other parts of the building just a short distance from the border.
- Adjacent buildings should be inspected for possible seating, cracking, movement of boundary walls, deformation of doors and windows, or roof slumps, and if necessary new walls from inside the building along the boundary wall, wall reinforcement Through the implementation of reinforced concrete walls and cement plaster, the implementation of filling walls in border wall openings, the boundary wall trimming, and the installation of appropriate piles under roof beams in appropriate locations within the adjacent building.
- With the permission of the relevant authorities, the warning signs were installed in the appropriate places for pedestrians not to park and not to park or pass cars around the dump site. Appropriate low-weight fencing should be created around the wall of the pit at appropriate intervals, and even possible demolish the heavy walls around the pit before digging.
- Prior to excavation, all sewage wells located in adjacent buildings should be identified as far as possible. If the wells distance from the bottom of the well is less than the final depth of the well and the water level of the well is higher than the bottom of the well, prevent drainage and prevent water from spilling into them. Wastewater wells at this distance shall be filled with suitable materials and farther away new wells shall be blocked and the paths of sewage pipes leading to the filled wells shall be blocked and the new sewage and runoff transmission system shall be transferred to the new wells.
- Identify canals, tables, culverts and water and wastewater transfer facilities adjacent to the digging passages and seal them with appropriate waterproofing if possible within the digging wall.
- Adjacent garden gardens are identified and suitable solutions are found to prevent flooding.
- Route of all vital arteries such as gas line, water, high or low voltage, telephone, optical fiber and internet etc. and its passage in the adjacent digging passages with inquiries from relevant authorities, identifying and if crossing the adjacent digging border. Anticipated additional safety precautions.
- Prior to any demolition and demolition, adjacent buildings shall be subject to financial and criminal risks and civil and third party liability and. . . Insured.
- Demolition and excavation under the supervision of the supervising engineer or supervisor shall be carried out by the competent authority.
- At all times, appoint a person to inspect the existing safety wall and to keep a watchful eye on the wall and to alert workers to danger, shelter or any reaction needed. It is even possible to install an alarm system at the workplace to alert workers and residents of adjacent buildings.
- Keep up-to-date records of workshop workers with specifics, addresses, and phone numbers at specific offices.
- During the excavation step design procedures should be implemented in the same way. At no stage of the excavation and execution of the guard structure should the wall of the excavation be abandoned for a long period of time and the speed of follow-up should be maintained.
- Digging is done in a step-by-step manner in the executed maps using special machines or manual methods.
- During the excavation and installation of structures and afterwards, adjacent buildings and passages must be inspected regularly. Creating or increasing cracks in the walls, ceilings and floors of adjacent buildings and passageways and under the pressure or release of door and window pre-pressures, breaking or cracking glass, soil or soil swelling, mosaics or floor coverings On the floor, wall or ceiling, the sound of fracture of the structural and non-structural elements of the adjoining building may be due to the movement of the earth. In such cases, the matter must be dealt with urgently. Identified the weaknesses of elements of the guard structure that could be effective in this issue and reinforced the guard structure by reinforcing those elements or adding new elements.
- If the soil part of the digging wall is darker than the rest of the soil, it may indicate the presence of cavities or wells adjacent to the digging boundary and the likelihood of instability in these areas is greater. Therefore, depending on the type of observed phenomenon, additional stabilization strategies should be considered for that area.
- If the moisture content of a part of the sump wall increases during or after the sowing period or when water falls from part of the sump wall into the sump, it indicates that there was a source that caused this moisture. There may be absorption wells, water leaks from the water or sewage network, irrigated orchards, or groundwater passing through coarse-grained layers that are somehow related to the water source. In this case, the probability of lowering the wall wall’s stability is likely to be high, and appropriate solutions should be taken to remove the source of moisture and immediately increase the capacity of the guard structure locally in the same area.
- If during the installation of a guard structure or after one of the structural elements such as a wall, bracket restraint, beam, column, column foundation, or foundation for the reinforcing pressure forces or horizontal elements reducing the lateral buckling length of the brackets Reaching its limit or buckling or rupture state indicates the use of forces exceeding the capacity of the guard structure, in which case the problem must be immediately investigated and the guard structure reinforced.
- Avoid the establishment of a chamber, canopy, residence or restroom for the guard or workers or the warehouse adjacent to the excavation site and for such cases a location that is within a reasonable distance from the excavation boundary.
- The complete lighting system shall be provided for the site of the digging site and shall be illuminated at all times at all parts of the workshop so that any part of the guard structure or the digging wall can be clearly seen from the outside.
- A vehicle equipped with first aid kits should be ready at the project site so that they can be treated or transported to treatment centers in the event of an accident.
- Even when possible during the night and during the rains, it is possible to avoid digging in the vicinity of the digging border. If burial is required in such cases, burial should be performed in the presence and supervision of the supervising engineer.
- Welding, construction and installation of guard structures shall be carried out by technically skilled workers. Always, even after the completion of the guard structure, a number of workers are technically ready to work and equipped with all the equipment needed to install or reinforce guardrail elements.
- In case of rain, if part of the wall is exposed to rain and the wall of the guard structure is not completed, it is necessary to cover it with a suitable plastic seal to the floor so as to prevent water from penetrating the wall and foot. .
- When digging and constructing a guard structure at groundwater level, consideration should be given to digging and guarding structures appropriate to the situation, taking into account drainage and drainage methods, piles, shingles, and so on. It is even possible to ignore the methods of implementing a wall in situ in such cases. In the case of emergency, people residing in buildings should evacuate the building as soon as possible, taking into account all the precautions of valuables and heavy luggage away from the vicinity of the dump site.