Kazemat, Betonnen werken omgeving Fort bij Tienhoven Tienhoven (Stichtse Vecht 26)

English translation

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Description

Cluster 21. Remnant Cast Steel Cupola Casemate Type G.

NEW HOLLAND WATERLINE

Introduction

Remnant of a CAST STEEL CUPOLA CASEMATE TYPE G as a deconcentrated, added to an existing concentrated defensive work, the Fort near Tienhoven, armed concrete work. In 1936, as a supplement to the armed 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 armour cupolas used were small in size (favourable with regard to visibility and hit probability), circular in form (favourable with regard to deflecting hits and strength), relatively simple to produce in series and they had an 'external' firing aperture (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 units in the Netherlands (at DEMKA) was, however, followed by a second order of 50 units from the Belgian Soc. Anonyme John Cockerill. In total, well over 700 must have been cast in a short time, but only a few of these 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 places in the Dutch lines, particularly in the IJssel Line, the Meuse Line, the Grebbelinie (each approx. 150) and the New Holland Waterline (approx. 80). The usual construction of reinforced concrete with one or more fixed gun apertures was hereby abandoned in favour of a system that had, within variable limits (up to 270 degrees), a projectible firing direction, 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 to a standardised design and consist of a cast steel cupola (usually removed), which is anchored in a reinforced concrete work. On the front side there was a firing aperture with a cantilevered section - an 'eyebrow' for protection of the weapon - and on the other side an entrance closed by a steel door. The firing aperture in the cupola formed a rounded, rectangular 'eyebrow' of approximately 10 cm thickness, which protruded some decimetres outside the cupola and provided protection to the weapon positioned inside. The concrete work consists of a relatively low rectangular structure, with a bevelled section on the front side, to achieve maximum field of fire. The standard armament consisted of a heavy machine gun. The firing aperture and the access to the casemate could be sealed 'gas-tight' from inside.

During the Second World War, the vast majority of cupolas in the interior were demolished by the occupier from the casemates - partly by blowing them up - to remelt them for other steel needs. On the coast, they were partly incorporated into the defence, but were mostly demolished again after the war. As a result, complete cupola casemates are rare, but they are found, among other places, at the Fort near Vechten. The concrete structures in which they were placed occur more frequently - but usually in damaged form. The remaining example of the cupola casemates within the complex of Concrete Works surrounding Fort Tienhoven is located approximately 800 m to the southwest of the fort near the Vecht bank, which served as the main defence line. This example too has been preserved only as a concrete remnant.

Description

Remnant of a CAST STEEL CUPOLA CASEMATE TYPE G, as a survivor of a type of casemate of which examples were constructed at various places in the Dutch lines shortly before the beginning of the Second World War. Standard cast steel cupola casemates type G are relatively low, virtually square, concrete casemates (approx. 7.00 x 6.50 x 2.20 m; w x d x h), with at the height of the space hollowed out for the cupola a rearward sloping surface. At the rear, a recess was made in the concrete to allow access to the cupola. The cupola casemate was blown up during the course of the Second World War, after which the cast steel cupola was removed and only the damaged reinforced concrete block remained as a remnant.

Valuation

The remnant of the CAST STEEL CUPOLA CASEMATE TYPE G to the southwest of the Fort near Tienhoven is of general importance because of:

* Cultural-historical values as part of the New Holland Waterline 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 'living' field fortification in depth (20th century).

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

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

* The component is reasonably representative as it has remained clearly recognisable as a remnant of a reinforced concrete gun shelter.

* The component is poorly preserved due to deliberate dismantling in the period 1940-1945, but it nevertheless exhibits physical characteristics by which its former function remains recognisable.