Kazemat, Betonnen werken Ruigenhoek-De Gagel De Bilt

English translation

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Description

Cluster 32. Concrete block of cast-steel dome casemate type G.

NEW HOLLAND WATER LINE

Introduction

CONCRETE BLOCK OF CAST-STEEL DOME CASEMATE TYPE G as remnant of linear and access defence with trench systems, group shelters and the like. In 1936, as a supplement to the reinforced concrete casemate, the so-called cast-steel dome casemate was introduced in the Netherlands, which was based on a system already applied in France in 1917. The armour domes used were small in size (favourable with regard to visibility and target probability), round in shape (favourable with regard to ricochet of projectiles and strength), relatively simple to produce in series, and they had an 'external' gun port (favourable with regard to gases and noise). Moreover, they could be manufactured in the Netherlands, which substantially reduced dependence on foreign suppliers. A first order of 100 units in the Netherlands (at DEMKA) was followed by a second order of 50 units with the Belgian Soc. Anonyme John Cockerill. In total, over 700 must have been cast in a short time, but only a few of these have survived. The cast-steel domes, with a diameter of 1.75 m and thicknesses of 10-17 centimetres, were installed in multiple casemate types with resistance classes W 12-15 to W 21-28.

Shortly before the beginning of the Second World War, so-called Cast-Steel Dome Casemates Type G were erected at various locations in the Dutch lines, particularly in the IJssel line, the Meuse line, the Grebbe line (each approximately 150) and the New Holland Water Line (approximately 80 in a reinforced version with a wall thickness of 14 cm). The usual construction of reinforced concrete with one or more fixed gun ports was abandoned in favour of a system that possessed a shooting direction projectable within variable limits (up to 270°), within a cast-steel cylinder with dome roof. Most domes were placed in the Dome Casemates Type G. Cast-Steel Dome Casemates Type G were built to a standardised design and consist of a cast-steel dome (usually removed), which is anchored in a reinforced concrete structure. On the front side there was a gun port with a projecting component - an 'eyebrow' for protection of the weapon - and on the other side an entrance closable by a steel shutter. The concrete structure consists of a relatively low rectangular building, with a bevelled section on the front side, to achieve maximum field of fire. The standard armament for dome casemates in the New Holland Water Line consisted of a heavy machine gun. The gun port and the entrance to the casemate could be sealed 'gas-tight' from the inside.

During the Second World War, the vast majority of domes in the interior were demolished by the occupier from the casemates - partly by blowing them up - to be recast for other steel requirements. At the coast they were partly incorporated into the defence, but were mostly demolished after the war. As a result, complete dome casemates are rare, but they are still found, among others, at Fort bij Vechten and Fort Everdingen. The concrete structures in which they were placed are found more frequently - but usually in damaged form. The preserved specimen within the complex Works between Fort Ruigenhoek and Fort De Gagel lies approximately 500 m to the south-west of Fort Ruigenhoek, in the immediate vicinity of a pair of Group Shelters Type P.

Description

The CONCRETE BLOCK OF CAST-STEEL DOME CASEMATE TYPE G (1939-1940) is the remnant of a relatively low, nearly square, concrete casemate (approximately 7.00 x 6.20 x 2.50 m; w x d x h), with, at the height of the space hollowed out for the dome, a backward-sloping surface. On the rear side an indentation in the concrete to allow entry to the dome. The specimen has been blown up and, as a result, shows serious concrete damage; the dome has been removed and remelted. The specimen is not accessible.

Valuation

The remaining CONCRETE BLOCK OF CAST-STEEL DOME CASEMATE TYPE G within the complex Works between Fort Ruigenhoek and Fort De Gagel is of general importance because of:

* Cultural-historical values as part of the New Holland Water Line as designed by C.R.T. Kraijenhoff and initially from 1815 realised by him, Jan Blanken and major-engineer Willem Offerhaus and subsequently reinforced and improved by others over approximately 125 years.

* Architectural-historical values, in particular as an expression of military-strategic building, which is based on the system of: a. the system of inundation and access defence (20th century), b. the race with strengthening offensive means (20th century), c. the system of 'living' field fortification in depth (20th century).

This concerns a component from the period 1939-1940, namely a reinforced concrete remnant of a standard cast-steel dome casemate.

* Ensemble value and situational values as part of the New Holland Water Line in general and because of the mutual functional, functionally-spatial and physical coherence with the remaining components of the complex.

* The component is representative (characteristic) because it is clearly recognisable as part of a deconcentrated defence line and as defence of an access added to the existing fortification system and because it has remained recognisable as such in the field.

* The component is reasonably well preserved because important physical characteristics, despite deliberate, partial dismantling, have remained recognisably present.