covered with a 3D cm layer of so-called shell-clay,, which is a 

 natural deposit often found in the fladden-sea, containing clay and 

 shells and being slightly permeable. Three layers of compacted 

 broken basalt stone (3-5 cm) were placed upon this,, each of -which 

 was penetrated with pure asphaltic bitumen 60/70. Although the 

 cambered slope was rather flat, the construction proved unstable 

 and slides occurred . Probably high ground water pressure under the 

 construction was the main reason for this failure since a high 

 range of dunes was near. The bituminous protection was removed 

 after some years and replaced by a brick pavement' on shell -clay. 



Repairs On the Outer Slope of the Westkapel Seadike 9 1946-47 , 

 (Figure 2) 



The Westkapel sea dike was badly damaged during the 

 struggle for Walcheren by bomb and shell explosions over a 

 section north of the gap which was made in 1944° This damage 

 was spreading gradually under the action of high tides. 



Part of the slope protection was repaired with concrete j else- 

 where pouring asphalt was used extensively to form a protection in 

 a quick and efficient way out of the loose stones which were pre- 

 sent on the slope . 



Furthermore , part of the slope was protected at the top by 

 a layer of rubble stone penetrated with asphalt. 



Test lb. Penetration of rubble stone with asphalt mastic. 

 Area IV, from +5«00 to +7.25 m N.A.P. was protected 

 by a 0.20 m layer of dumped rubble stone, penetrated 

 with asphalt mastic (15$ bitumen, 1% filling and 78$ 

 sand), in such a way that an impervious asphalt cover 

 was obtained at the surface. 



The rubble stone layer was filled to a depth of 

 10 cm by 110 kg of asphalt mixture per m^ (Figures 3 

 and 4)° In order to prevent the spaces in the rubble 

 stone being filled with water which might create a 

 dangerous pressure, the penetrated section was sealed 

 at the top by an asphalt coffer. This construction 

 has proved satisfactory, but it cannot resist water 

 pressure from beneath. 



Test 2d. Grouting of set stone and dumped stone with 

 pouring asphalt. 



In 194-6 an area was repaired by simply arranging 

 the old and worn basalt stones in a more or less 

 orderly manner and filling the voids with pouring 

 asphalt. As the voids were large (50$) an average of 



32 



