How do driving thrusts influence the design and verification of the pipeline?

Q: How do driving thrusts influence the design and verification of the pipeline?

Los empujes de hinca influyen directamente en el diseño y verificación de la tubería porque determinan las cargas longitudinales que la conducción debe resistir durante la instalación. Antes de ejecutar una hinca, es necesario comprobar que tubos, juntas, anillos de reparto y sistema de empuje pueden soportar los esfuerzos previstos sin fisuración, deformaciones, pérdida de estanqueidad ni daños estructurales. Los empujes dependen de la longitud de hinca, diámetro exterior, material de la tubería, geotecnia, nivel freático, profundidad, radio de curvatura, lubricación y tipo de tuneladora. Si los empujes previstos son elevados, puede ser necesario cambiar la clase resistente de la tubería, mejorar juntas o anillos de reparto, ajustar la lubricación, dividir el tramo, modificar pozos, incorporar estaciones intermedias de empuje o revisar el trazado.

The driving forces directly influence the design and verification of the pipe because they determine the longitudinal loads that the pipeline must withstand during installation. Before driving, it is necessary to check that pipes, joints, split rings and thrust system can withstand the expected stresses without cracking, deformation, loss of watertightness or structural damage.

In a work of pipe ramming o microtunneling in terrestrial and subway applications, In addition, the pipe must not only fulfill its final function in service. It must also be prepared to withstand the temporary installation loads generated by the thrust from the attack shaft.

What factors condition the driving forces?

The expected thrusts depend mainly on:

Pile-driving length: the greater the distance between the attacking and receiving wells, the greater the accumulated friction tends to be.
Outer diameter of the pipe: affects ground contact, excavated volume and friction surface.
Material and resistance of the tube: reinforced concrete, GRP, steel or other materials have different capacities and verifications.
Geotechnics of the layout: Adhesive clays, dense sands, gravels, fractured rock or mixed soils can increase the effort required.
Water table and water pressure: The stability of the face, the friction, the excavation and the tunnel boring machine system are all factors that influence the stability of the face, the friction, the excavation and the tunnel boring machine system.
Depth and coverage: influence the ground pressure on the driving surface.
Radius of curvature: curved layouts can increase lateral contacts and localized stresses.
Lubrication: Proper lubrication reduces soil-pipe friction and helps control thrust.
Type of tunnel boring machine and excavation method: the choice of tunnel boring machine conditions front-end control, performance and forward resistance.

What is verified in the pipeline

To validate the pipe in a drive, several technical aspects are reviewed:

Longitudinal resistance:
The pipe must withstand the compressive stresses generated during thrust without exceeding its allowable capacity.

Behavior of the joints:
The seals must maintain alignment, transmit loads correctly and maintain tightness during installation and in service.

Delivery rings or support elements:
They are used to distribute the thrust stress and avoid load concentrations that can damage the pipe edges.

Ovalization or deformation:
In certain materials or diameters, it is verified that the pipe does not suffer deformations incompatible with its final use.

Compatibility with curves:
In curved layouts, radii, angular deviations in joints, eccentric stresses and lateral contact with the ground are checked.

Internal or external pressure in service:
In addition to the installation loads, the pipe must meet the hydraulic, structural and sealing requirements of the final pipeline.

When it may be necessary to adjust the design

If the expected thrusts are high, the design may require:

Change the material or strength class of the pipe.
To increase the admissible capacity of seals or delivery rings.
Improve the lubrication system.
Reduce the driving length by dividing the span.
Modify the location of vertical pits for driving and microtunneling.
Incorporate intermediate push stations.
Adjust the layout to avoid overly demanding curves.
Review the excavation method or type of TBM.

These decisions must be made before closing the design or bidding the work, because they affect the budget, schedule, pipe supply, logistics and safety of execution.

What risks a correct verification avoids

A correct verification of thrust helps to avoid cracks, pipe ruptures, joint damage, loss of watertightness, stoppages, cost overruns, changes of method during the work and problems in the final reception of the pipeline.

In complex projects, such as infrastructure crossings, In the case of long lengths, large diameters or high friction soils, this review is critical to ensure that the solution is constructible and that the pipe is compatible with the driving procedure.

Minimum checklist to verify driving thrust: driving length, outside diameter, pipe material, strength class, allowable thrust, joint type, split rings, geotechnics, depth, water table, expected friction, bending radius, lubrication, intermediate stations, frame capacity and execution tolerances.

Request a technical review of thrust and verification of pipe to be driven before closing the design, preparing the tender or defining the pipe supply.