Kazemat, Voordorpsedijk Groenekan (De Bilt 26)

English translation

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Description

Cluster 36. Concrete block of cast steel cupola casemate type G.

NEW HOLLANDSE WATERLINIE

Introduction

CONCRETE BLOCK OF CAST STEEL CUPOLA CASEMATE TYPE G as a remainder of linear and accessory defence with trench systems, group shelters and the like. In 1936, as a supplement to the reinforced concrete casemate, the so-called cast steel cupola casemate was introduced in the Netherlands, which was based on a system already applied in France in 1917. The armoured cupolas used were small in size (favourable with regard to visibility and hit probability), round in shape (favourable with regard to deflecting hits and strength), relatively simple to produce in series, and they had an 'external' firing opening (favourable with regard to gases and sound). Moreover, they could be manufactured in the Netherlands, which significantly reduced dependence on foreign countries. A first order of 100 pieces in the Netherlands (at DEMKA) was followed by a second of 50 pieces from the Belgian Soc. Anonyme John Cockerill. In total, more than 700 must have been cast in a short time, but only a few have survived. The cast steel cupolas, with a diameter of 1.75 m and thicknesses of 10-17 centimetres, were installed in several 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 Cupola Casemates Type G were constructed at various locations in the Dutch lines, notably in the IJssel line, the Maas line, the Grebbe line (each approximately 150) and the Nieuwe Hollandse Waterlinie (approximately 80). The usual construction of reinforced concrete with one or more fixed firing apertures was abandoned in favour of a system that possessed a firing direction projectable within certain limits (up to 270°), within a cast steel cylinder with cupola roof. Most cupolas were placed in the Cupola Casemates Type G. Cast Steel Cupola Casemates Type G were built according to a standardised design and consist of a cast steel cupola (usually removed), which is anchored in a reinforced concrete structure. On the front side there was a firing aperture with a projecting part - an 'eyebrow' to protect 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 cupola casemates in the Nieuwe Hollandse Waterlinie consisted of a heavy machine gun. The firing aperture and the entrance to the casemate could be sealed 'gas-tight' from within.

During the Second World War, the vast majority of cupolas inland were demolished by the occupier from the casemates - partly by blowing them up - to be recast for other steel needs. On the coast they were partly incorporated into the defence, but were mostly demolished after the war nonetheless. As a result, complete cupola casemates are rare, but they still exist, among others, at the Fort bij Vechten. The concrete structures in which they were placed are more common - but usually in damaged form. The preserved specimen within the complex of Concrete Works between Fort Blauwkapel and Fort Voordorp is located approximately 75 m to the north-west of the northern bastion of Fort Voordorp, in the immediate vicinity of a Group Shelter Type P. Both are situated on a farm yard (Voordorpsedijk no. 35), among business buildings. The front side faces south-west, allowing frontal fire on the Voordorpsedijk at the fort and also the defence of the Looydijk and the Groenekanse Dijk.

Description

CONCRETE BLOCK OF CAST STEEL CUPOLA CASEMATE TYPE G (1939-1940) as a remainder of a relatively low, almost 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 cupola, a rearward sloping surface intended to deflect incoming enemy fire. On the rear side a cavity in the concrete to allow access to the cupola. The specimen has been blown up and as a result shows serious concrete damage; the cupola has been removed and remelted. The specimen is not accessible.

Valuation

The CONCRETE BLOCK OF CAST STEEL CUPOLA CASEMATE TYPE G within the complex of Concrete Works between Fort Blauwkapel and Fort Voordorp is of general interest because of:

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

* Architectural-historical values, in particular as an expression of military-strategic architecture, which is based on the system of: a. the system of inundation and accessory defence (20th century), b. the race with increasingly 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 remainder of a standard cast steel cupola casemate.

* Ensemble value and situational values as part of the Nieuwe Hollandse Waterlinie in general and because of the mutual functional, functionally-spatial and physical coherence with the other components of the complex.

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

* The component is reasonably well preserved because important physical characteristics, despite wilful, partial dismantling, remain recognisably present.