Bomvrij militair object, De Bilt

English translation

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Description

Cluster 31. Group Shelters Type P.

NEW HOLLANDIC WATERLINE

Introduction

GROUP SHELTERS TYPE P on and near Fort Ruigenhoek are 20th-century, mass-produced additions to the existing fortification. (Concrete) (group) shelters were a response to the arrival of heavy projectiles and high-explosive grenades. The latter have a highly explosive charge. The earliest types of concrete shelters offered only protection against grenade fragments and were termed 'splinter-proof'. According to the weight of the artillery and the protection against it, there is a classification into resistance or protection classes, consisting of two numbers, e.g. W 12-15. The first indicates that the cover is sufficient for impacts of projectiles up to that calibre (in cm); the second that protection also exists against one or at most a few impacts up to this higher calibre. The Group Shelters Type P were built according to a more or less uniform or standard design in the years 1939-1940 at multiple locations in the Netherlands. The total number of built examples amounts to approximately 700, of which around 570 in the New Hollandic Waterline; the majority (approximately 400) of these still exist. The construction programme for the Group Shelters Type P was not completed at the outbreak of the Second World War and a number of examples have remained visibly unfinished. Type P (also called 'the pyramid' due to its distinctive shape) is presumably the most well-known type of concrete defensive structure in the Netherlands. The type originated from the so-called VIS 77 (Regulation for Setting Up Positions no. 77), from 1928, and had as one of its purposes to form part of the defence of a number of new accesses, including in particular (motor) roads. The Group Shelter Type P usually came into being in the immediate vicinity of already existing or contemporaneously realized casemates, gun emplacements, fortifications or trenches. The hitherto entirely closed front or front face of the Group Shelters Type P was intended to be covered by earthworks, which could form part of a glacis for the protection of the trench or a covered way. These earthworks are now mostly no longer present or only with difficulty recognizable, but particularly on forts or in otherwise topographically marked terrain, there is sometimes still cover or there are remains that are recognizable. There exist various variants of Type P, both in terms of dimensions and protection class as in execution and detailing. Thus there are examples built in protection classes W 12-15 and W 21-28 with dimensions ranging from approximately 5.50 x 7.20 x 4.70 m to 6.50 x 8.20 x 4.90 m (w x d x h). Numerous examples of Type P were built in areas liable to inundation, in which in a number of cases a visible pile foundation has been applied, while often a retaining wall or trough with stairs against inundation water has been incorporated in the then elevated, square access and in still others a concrete foundation slab projecting all around is present. At various locations on and around Fort Ruigenhoek, Group Shelters Type P are located. Of these, 11 are reckoned to belong to this complex; they are indicated on the map belonging to this document. They are all oriented with the access opening on the west-southwest side (turned away from the enemy's main line of fire) - not exactly towards the original gorge side of the fort. They are only limitedly provided with an earth cover, but there are recognizable remains of trenches or other works; more traces or remains of these may be present.

Description

GROUP SHELTERS TYPE P are single-storey, usually in reinforced, approximately 100 to 180 cm thick cast concrete, shell-proof, military shelters, which could provide protection for 10-12 infantrymen/artillery personnel. Group Shelters Type P are built on a rectangular ground plan. The visible height above ground level varies. Both blind side walls and the gorge are executed vertically to a height of approximately 3 m. Above this, these walls slope inward at an angle of approximately 45 degrees, then transition into a flat roof. On the right in the gorge is an (later either sealed or left open) access opening at locally varying height above ground level. The entirely vertical, closed front wall mirrors the 45-degree angles and thus ends as a 'truncated pointed gable'. In a number of cases, iron hooks were cast into the wall(s) that could serve to secure camouflage material. A characteristic component on top of the Type P shelter is the conical, concrete 'outlet', which was intended for the mounting of a periscope. These periscopes were, however, never actually mounted in practice. The interior of the Group Shelters Type P consists of a short corridor (usually with a concrete retaining wall or balustrade and usually a few descending steps) and an 'airlock' directed from there to the left, which could be sealed by a (consisting of multiple parts) heavy, steel door with bolts. Via a second, similar door, a rear, nearly square space could be reached on the right, the actual shelter. The access could be controlled from this space via a gun port. The doors were, however, rarely or never actually mounted in practice. The ceilings, located at approximately two metres above floor level, are flat and rectangular. In a number of cases, interior components are still present, such as (remains of) wooden benches or a support for the firearm for controlling the entrance. The examples belonging to the Fort Ruigenhoek complex are scattered on and near the work - mainly on the frontal rampart sides.

Valuation

The GROUP SHELTERS TYPE P on and near Fort Ruigenhoek are of general importance because of:

* Cultural-historical values as part of the New Hollandic Waterline as designed by C.R.T. Kraijenhoff and initially from 1815 realized by him, Jan Blanken and major-engineer Willem Offerhaus, and subsequently by others over more than a century strengthened and improved.

* Architectural-historical values, in particular as an expression of military-strategic building science, which is based on: a. the system of inundation and access defence (nineteenth and twentieth centuries), b. the race with increasingly strengthening offensive capabilities (nineteenth and twentieth centuries), c. the system of 'living' field fortification in depth (twentieth century).

These are components from the period 1939-1940. These components are examples of reinforced concrete enlisted shelters.

* Ensemble value and situational values as part of the New Hollandic Waterline. Also because of the functional and physical coherence with the other components of the complex.

* The components are representative (characteristic) because as part of a deconcentrated defence line they were added to the existing defence system and were thereby built on an existing fort.

* The components are reasonably well preserved and as built components can be well recognized in the field.