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Our Approvals 

PORR Spezialtiefbau GmbH holds many national technical approvals. This means every customer can be confident in the knowledge that we have the technical know-how to complete any construction task, no matter how specific. All certificates are only available in German.



Stump soil nailing system - Every slope reliably secured.

The temporary or permanent securing of steep inclines and construction pits using soil and rock nails is a key feature of PORR’s range of activities. This proven construction method, which has received general building approvals, has been greatly influenced and developed by our company since its first appearance on the market.

Tight-connecting round bars, or nails, are arranged in such a way as to securely absorb any earth pressure that may arise in the loose rock of a monolithic body. GEWI steels are used as supporting elements. These are encapsulated in a ribbed pipe injected with a cement suspension to prevent corrosion in permanent installations. 

Depending on the application, it may be possible to use cuttable tension elements made from fibreglass, known as GFK elements, or self-tapping nails to secure tunnel driving works. The upper surfaces, where loose rock is first secured by soil or rock nails, are then stabilised with a statically measured and reinforced layer of shotcrete. The ideal arrangement and dimensioning of the necessary securing elements is calculated by our engineers using state-of-the-art calculation procedures.

Approval (PDF): Bodenvernagelung System Stump (Z–20.1–104)  (only available in German)

Stump jet grouting method - Stump jet grouting method

PORR Spezialtiefbau GmbH is one of the first companies in Germany to receive national technical approvals for jet grouting methods. Owing to our continuous improvement of individual components, we are able to guarantee a high level of execution reliability.

 With the publication and introduction of DIN EN 12716:2019-03 "Execution of special civil engineering works - Jet grouting; German version EN 12716:2018" as a technical building regulation, the planning and execution of load-bearing elements using jet grouting or high-pressure injection methods are regulated (see MVV TB, No. A general type approval is no longer required. The use of subsoil improvement methods is permitted by the building authorities and does not require a type approval. 

Jet grouting methods are used for:

  • Underpinning
  • Sealing bases
  • Sectional sealing
  • Sealing blocks
  • Reinforcement of foundations
  • Soil improvement

Approval (PDF):  Düsenstrahlverfahren Stump Jetting (Z-34.4-5) (only available in German)


Stump Duplex permanent anchors - With specialised pressure pipe.

The patented Stump Duplex anchor was the first permanent anchor to receive national technical approval in Germany, and the first permanent anchor to be released from the requirement of subsequent monitoring. For over 40 years, this permanent anchor system has been used as a permanent anchor for applications intended to last for more than two years.

The Stump Duplex anchor is a pressure pipe anchor in which the force is transmitted via the back end of the injection body within the pipe. The so-called Duplex pressure pipe works as a force transmission element. The anchor steel tension member is not connected to the grout body. The grout body transfers force from the end of the anchor via compressive force into the subsoil, and so a formation of cracks in the grout body and resulting reductions in the force transmitted between the grout body and the surrounding soil are not to be expected.

Approval (PDF):  Stump-Duplex Daueranker für Boden und Fels (Z-20.1-6)  (An application for extension has been made) (only available in German)

Stump rock anchors - Suitable for use even in solid rock.

Stranded rock anchors are the best example of progress and evidence of the advances in modern anchoring techniques for solid rock faces. These anchors are generally used only where the entire length of the force transmission area comprises solid rock. However, Stump rock anchors may be used in other circumstances with the approval of a geotechnical expert. 

The use of specialised grouting techniques enables reliable, heavy-duty bolt anchors to be used with even the most difficult soil types and rock formations

Developmental milestones.

Works on the Eder dam wall represent a significant milestone in the development of the Stump rock anchor system. Buoyancy control for the Eder dam wall was provided by 104 stranded permanent anchors of type 6-34 with a load resistance of 4,500kN. Test loads applied up to 12,500kN of force to anchor lengths of between 68m and 73m. In this project, it was essential to drill holes into the dam wall with great care and precision across the entire area. Drilling discrepancies of 0.5% represented a figure well below the 1% variation allowed.

Holes with a diameter of 146mm were coredrilled prior to the fabrication of the rock anchors. These holes were then expanded to a diameter of 276mm. Cement-based grout injections into the mountainside and walls enabled us to apply targeted tempering to the area, particularly in the force transmission area around each anchor. This was verified using WD tests (lugeon tests). A mobile crane and special deflection construction were used to install the anchors, to avoid damage to the anchor encapsulation during installation.

To tension each anchor, we used a prestressing jack developed specifically for this purpose. 10 out of 104 built-in anchors were equipped with force measuring boxes and fibre-optic cable sensors for permanent ongoing monitoring of the anchors. All the anchor heads are designed so that the pressure on the anchor can be measured at any time, and the anchor tensioned if necessary.

A large fissure in the Kammereck rock face, between St Goar and Oberwesel, was secured with the installation of 23 permanent rock anchors with a load resistance of 2,000kN each. The rock massif looms directly above the heavily-trafficked national highway B9, which passes through a Deutsche Bahn railway tunnel beneath the rock. Each of the up to 40m-long permanent anchors is composed of 23 individual strands arranged along two reinforced concrete cross bars. The service load was increased in two stages, first to 1,350kN and then to 2,000kN. We are constantly monitoring the deformation of the cliff face via multiple extensometers.

Approval (PDF): Felsanker (Z-34.11-223) (only available in German)

Stump HLV pile system - High loads, fast installation

HLV piles are pipes made from ductile cast iron, assembled from partial lengths to create the total pile length. The partial lengths are connected using dedicated ductile cast iron pile sleeves or special coupling parts and then driven into the soil with pile drivers. The ramming process creates a rigid, form-fitting and friction-locked connection. Depending on the soil quality, a spike tip or ram shoe may be used to insert the pile.

The so-called ductile piles may be used either grouted or non-grouted and as pressure or tensile piles. They can be fabricated vertically or on an angle and inserted to depths of up to 55m.

Der Einsatz sogenannter Duktilpfähle erfolgt entweder verpresst oder unverpresst als Druck- und/oder Zugpfähle. Zudem ist ihre Herstellung vertikal oder geneigt bis zu 55 m Tiefe möglich.

HLV piles are available with the following specifications:

  • Diameters of 118mm and 170mm
  • Load transfer of up to 1,400kN

Approval (PDF):  HLV-Pfahl System Stump (Z-34.25-203) (only available in German)

Stump compact anchors - For rock and soil.

Compact anchors, also known as pressure-grouted anchors, can be used for a wide variety of applications. One of the most common uses of this method is the temporary securing of construction pits for a period of less than two years. 

Permanent anchors such as stranded compact anchors are used with demonstrable success to anchor pavilion roofs, bridges, slopes and supporting construction works. However, this technique can also be efficiently and economically applied to smaller projects. One example of this is the pylon anchoring system of the pavilion roof construction of the all-weather swimming pool in Velbert. 

Compact anchors are also commonly used in bridge construction. The construction of the Kylltal bridge is one such case, in which the dispersal of force from the cantilevering construction required the use of 58 anchors on each side with resistant strength of 2,700kN each. On one side of the bridge abutment, the necessary foundation anchors could only be fabricated on a level much lower down than the subsequent foundation. As a result, the anchors had to be extended by approximately 7m after fabrication, in a similar manner to the creation of a coupling point, as is known from prestressed concrete. The entire work process was extensively monitored at the coupling point for quality assurance purposes.

Approval (PDF): Kompaktanker für Fels und Boden (Z-34.11-224) (only available in German)

Stump stranded pressure pipe anchors - Light load, plenty of strength.

Pressure pipe anchors such as the Stump stranded pressure pipe anchor are also known as pressure-grouted anchors. The anchoring force to be transferred to the ground is transmitted from the steel tension member via a steel pressure pipe from the anchor foot to the grout body, from which it then passes into the subsoil. A viscoplastic corrosion-protection encapsulation is used to backfill the remaining space between the steel tension member and the pressure pipe.

This anchor system combines the significant flexibility of stranded supporting elements with optimal force transmission via the pressure pipe.

Moreover, Stump stranded pressure pipe anchors can be used successfully in limited space conditions.

Approval (PDF):  Litzendruckrohranker für Boden und Fels (Z-34.11-205) An application for extension has been made (only available in German)

Stump composite pile system - Small but strong.

The Stump composite pile system can be implemented as a single-rod pile for pressure and tensile force up to 2,574kN. Sections of round bar with rolled thread ribs on both sides are arranged along the length of each pile as a supporting element. Composite piles can be coupled together for economical use in confined spaces with ceiling heights up to 2m. 

The rolled thread ribs create a friction-locked connection between anchor sections and anchor nuts, connecting individual pile sections with threaded sockets and improving the composite effect on the surrounding cement stone in the force transmission area. The profiling of these supporting elements means they can be precisely positioned in the pile head area and the desired length of pile protrusion can be achieved with approved connecting elements. With encapsulation applied as per the general building approvals, composite piles can also be used as tension piles to a load bearing capacity of 990kN. 

The construction method used for these piles enables them to be successfully fabricated even with minimal building heights of approx. 2m. Piles can also be constructed with the facility for subsequent re-injections for targeted improvement (post-grouting injections) of the surrounding soil in the force transmission area.

Approvals (PDF):