Anchor models, like other support works, must be defined before being used. The relative dialog window presents a table in which the different anchor models can be defined using the following characteristics:
No: Sequence number of the typology
Description: work description
No. of series/Step: the typology can be made up of one or more anchors: in the firs case insert 1; in the case of a series of anchors or nails it is possible to insert the number and the step, separated by the “/” character. In this last case the program generates a series of n anchors with the same characteristics.
Example: 10/0.5 is equivalent to a series of 10 anchors with a 0.5m spacing step between them.
The other items are necessary to define the geometry of the structural element.
The different typologies are: Active anchor, Passive anchor, Nailing. For each of these the work ultimate resistance must be assigned and will condition the stabilization according to the following cases:
Case 1
The sliding surface does not intercept the anchor (neither the free length, nor the foundation): in such a case is considered no contribution of resistance;
Case 2
The anchor is intercepted in the free length, so the foundation is anchored to the stable part: the tensile stress is considered as 100% resistant action and is inserted on the base of the slice that intercepts a force equal to the tensile stress. This force is subsequently decomposed into normal and tangential components, and the tangential component is inserted as a contribution to the shear strength on the sliding surface.
Case 3
The anchor is intercepted on the foundation, so the foundation comes into operation only for the resistant length over the sliding surface: the tensile stress, in this case, is considered with a defined percent of the ration between the resistant length and the length of the foundation. The action is treated like above.
For the cases 2 and 3 the traction refers to a section of unitary depth (dimension orthogonal to the section of the slope) as a function of the longitudinal distance (is multiplied by the distance).
Even if a series is intended, it is always assigned the ultimate strength of a single anchor or nail.
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For active works, the resistive component of the work along the sliding plane is subtracted from the Driving Forces. For passive works, the resistive component of the work along the sliding plane is summed to the Resisting Forces.
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Consolidation using Soil Nailing technique
The reinforcement technique of the soils using nails named “soil-nailing” consists of introducing reinforcements in the soil mass, having the function of absorbing stresses that the soil alone couldn’t be able to support.
The reinforcement system is a passive one; the soil adjacent to the reinforcement, at the time of its installation, is practically not solicited.
Resistance: the pullout resistance of the nails developed on the mortar-soil interface can be calculated using Bustamante method.
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