What is mutual inhibition or stratification? (Braced Excavations – Struts)
rose roofing: Soil pressure containment or in short mutual containment (strat) is one of the methods of stabilizing small width pits which is often used due to the lack of permission from the neighboring neighbors.
In this method, similar to the method of the truss guard structure, vertical members are installed at certain intervals, and then by placing a horizontal member between these vertical members, the deformation of the walls is prevented.
In pits with a small width, due to the lack of space for the execution of the inclined member of the truss, the method of the guard structure of the truss is practically excluded, and the mutual restraint method is a suitable alternative.
In this method, pressure members (pressure barriers) are used to transfer soil pressure. The components of this method are as follows:
1) Wall: In fact, in addition to resisting soil pressure, walls also act as supports for compression members. There are different types of walls such as:
Shield (Sheet Pile)
Diaphragmatic wall
Metal guardian candles
Concrete guardian candles
2) Pressure members (Strut or Brace): Pressure members or pressure restraints have the role of transferring soil pressure from one wall to another wall, which have different types. As:
Profile of the IPE couple
IPB couple profile
Pipe
the can
concrete section
3) Intermediate members (Wale): As it is clear from the name of these members, they have the task of transferring power from the wall to the compression members. The intermediate members take the applied soil pressure from the wall and transfer it to the compression members (struts). Therefore, struts and their connections are designed based on compressive force, intermediate members based on shear and bending force, and the wall is also designed based on combined forces.
Basics of design of mutual inhibition method (strat)
In order to design the pit using the mutual restraint method, the force created in the horizontal and vertical members should be calculated by simulating the project conditions in 2D or 3D software, and then the appropriate member should be designed for these members by controlling the ultimate limit states and exploiting them. The vertical and horizontal members are generally steel and are designed according to the code of steel structures.
Considering the phenomenon of buckling in the design of horizontal members is one of the important topics of the mutual restraint method.
Simulation of mutual inhibition by software
The method of execution of mutual attack (strat)
1. Drilling vertical member wells in the mutual containment method
Similar to the implementation of metal piles in the nailing, anchoring and truss guarding methods, in the mutual restraint method, the wells of the vertical members must be dug before the excavation. The location of these wells is done by mapping and according to executive plans.
In order to concrete the roots of the vertical members, the bottom of these wells is lower than the level of the foundation floor.
Concreting the roots of upright members
2. Execution of vertical members in the method of mutual restraint
Often, the cross-section of vertical members is in pairs of IPE profiles. The upright members are placed vertically in the well and completely attached to the wall, and then the root of the metal pile is concreted.
Installation of upright member with crane – Ista Sazeh Engineering Company
The root of the metal pile is about 25% of the depth of the pit and the diameter of the wells is about 80 to 100 cm. In order to better hold the vertical member in the root concrete, corner pieces or studs are welded to the vertical member as a cut-off.
Just as metal piles in the methods of nailing, restraining, truss guarding structure, etc., must be completely supported on the pit wall, for the proper functioning of the mutual restraining method, the vertical member must be completely attached to the wall to minimize deformations.
Stabilization of the well by the method of mutual containment in Vanak-Tek project
In order for the upright member to stick completely, its back is filled with suitable materials that have the minimum compressive strength of the soil of that part, so that no empty space remains between the upright member and the wall.
Considering that the horizontal members must be connected to the vertical members from both sides, therefore the vertical members are completely facing each other on the two opposite walls as much as possible to use their full capacity.
3. Execution of horizontal members in the method of mutual restraint
After the implementation of vertical members, the first row of horizontal members should be implemented. Horizontal members are in the form of profile pairs or tubes or…
Similar to connecting beams to columns in structures, horizontal members are connected to vertical members by welding and using steel sheets.
In order to prevent local falls, between the vertical members, wooden beams or steel mesh and concrete spraying (shotcrete) or other suitable members can be used.
The use of tubular members for horizontal members and the use of wooden timbers to prevent local falls
To reduce the effective length of the horizontal members, you can use a brace (a member perpendicular to the horizontal member). By doing this, the buckling of the horizontal members is prevented.
Implementation of cache to reduce effective length in Zafar project of Istasazeh company
4. Completing the horizontal members in the mutual restraint method
After the implementation of the first row of horizontal members, until reaching the level of the second row of horizontal members, excavation is done and the steel grid (mesh) and concrete spraying (shotcrete) are also implemented. This process continues until the end of the pit.
<img class=”entered exited” src=”data:;base64,” alt=”Implementation of diagonal reciprocating restraint in the Phoenix project – Istasazeh Engineering Construction Company” width=”650″ data-lazy-src=”/wp-content/uploads /2020/04/implementation-of-diagonal-interaction-in-the-Phoenix-project-construction-construction-partnership-of-static-structure.jpg” />
Implementation of diagonal mutual restraint in the Phoenix project – Istasazeh Engineering Construction Company
In some projects, due to various reasons such as the length of the opening, there may be a need for diagonal cross braces to obtain a more optimal plan by reducing the length of cross braces. For this purpose, in order to stabilize such projects, instead of opposite walls, the walls of M
