The "Method of the error function curve" was developed by Peck [Mair93] and modified by O'Reilly and New [New92] in order to also consider the depth position of the jacking.

The principle of the calculation method is the typical shape of the subsidence trough (Bild 15.2.1.1), that is defined by the Gaussian normal distribution function and calculated in accordance with Formel 15.2.1.1 :

(Image: Depth dependency of the error function curve [Scher77c])

The calculation method according to Scherle [Scher77c] is based on the assumption that the subsidence is caused principally by the loss of soil and thus also by the overcut. In this case, the subsidence line formed at the ground level (GL) will be approximately idealized by a line forming a trapezoid with respect to the existing surface (Bild 15.2.1.2) whose area is identical to the …

The calculation method according to Sagaseta [Sagas87] is based on the established principles of fluid mechanics.

In his analysis, Sagaseta [Sagas87] first assumed an infinitely deep tunnel. This is surrounded by a soil idealized as an incompressible fluid that approximates somewhat to cohesive soil in undrained conditions.

Assuming that a deformation vector is known, then the calculation of subsidence caused by a tunnel of finite depth is possible. …

The disadvantage of the method according to Sagaseta [Sagas87] (Abschnitt 15.2.2.1) is in the assumption of the incompressibility of the soil. This means that long-term deformations, which are generated by consolidation or creep, are not considered in the deformation calculation.

In order to compensate for this disadvantage, the factor α was introduced which takes into account the change of volume during pipe jacking.

With the use of α, radial deformations …

Included among numerical methods are the Finite Element Method (FEM), the Finite Difference Method (FDM), the Kinematic Element Method (KEM), the Boundary Element Method (BEM) and the Discrete Element Method (DEM).

The Finite Element Method is the most widely used method due to its multifaceted possibilities of application and its particular suitability for the depiction of the stress and deformation behaviour of complicated geometries and spatial …

(Image: Effects of soil deformation on adjoining structures [Attew86])

Critical for the effects of soil deformation on existing structures (Bild 15.3) are the

• Deformations during the construction phase
• Total deformations in the final condition
• Differential deformations in the final condition

Differential deformations cause displacement or deformation at existing structures, pipes and traffic surfaces and thus additional loading.

In order to estimate …

With trenchless pipeline construction methods, it is now possible to install cables and pipelines underground, irrespective of the outer diameter or nominal size and the geological and hydrogeological boundary conditions. The wide-ranging technical information in this standard reference book not only helps the user in the planning and execution of pipeline construction measures, but also provides a basis for an economically and technically optimal selection of the process technology. In detail, the technical book deals with the following topics: geotechnical fundamentals and investigations, unmanned, steerable and non-steerable methods (soil displacement methods, pilot pipe jacking, microtunneling, manned methods (pipe jacking), drilling fluids and drilling fluid technology, jacking control, surveying and monitoring, start and target shafts, calculation of jacking pipes, tendering and contract award information, and economic feasibility considerations.

Process: Static pipe bursting

Title: Replacement of a vitrified clay sewer DN 12 in (300 mm) and DN 16 in (400 mm) by static pipe bursting with HDPE pipes OD 18 in (450 mm) and OD 20 in (500 mm).

Location: Way of cultivation by agriculturally used areas without residential buildings

Limiting conditions:

• System: Wastewater sewer
• Material: Vitrified clay
• Shape of the cross section: Circular cross section
• Nominal …

Machines and equipment:

When employing static pipe bursting with the Grundoburst technique by Tractotechnik, Lennestadt the following machines and equipment are predominantly employed:

• Guide head
• Bursting body (stiff)
• Expanding body
• Shear resistant pulling- and pushing-rod also guaranteeing tensile strength
• Hydraulic power pack
• Pushing- and pulling-equipment with carriage

To connect the HDPE continuous pipes the following is required:

• Heating …

Site equipment

Site equipment includes traffic safety, provision and preparation of storage surfaces for equipment and material as well as the provision of power and water supplies.

Considerations of drainage capability

To maintain the drainage capability, the sewage is led off HDPE pipes DN 8 in (200 mm) which are provisionally laid aboveground from a point situated above the section that is to be rehabilitated via a distance of up to 360 ft (190 m) …

Sewer cleaning

In the pipe bursting a sewer cleaning by means of high pressure flushing is carried out directly before the replacement.

On the one hand it serves for the removal of deposits, incrustrations etc. and thus the prevention of failures in the bursting- or pulling-in procedure. On the other hand a soiling of the underground by the noxious matters which possibly adhere to the pipe fragments that remain in the underground is to be avoided.

Excavations

First the hydraulically driven pushing- and pulling-equipment with carriage for the pulling- and pushing-rod guidance is installed inside the target excavation and is braced. It is telescopable and can be extended in its length from 4 ft to 6 ft (1.2 m to 1.9 m) as a support of the wall of the excavation.

Important: A safe pulling- and pushing-rod guidance can only be ensured by a good fixation.

Replacement of a vitrified clay sewer DN 300 and DN 400 using the static pipe bursting method and insertion of PE-HD pipes DA 450 and DA 500.