The invention relates to a ground plate of reinforced concrete, for instance a road construction, an airport runway or a foundation for a building, said ground plate having a slab and tubes of reinforced concrete, said tubes being rigidly attached to the lower side of said slab and being spaced from each other. Such a ground plate is disclosed in NL-A-134.497 to be laid on soft ground with a pressure resis-2 tance of 0,2-0,3 kgf/cm .

The present invention provides a ground plate which can be laid on even softer ground. To this aim the uninterrupted great area of the slab and the other dimensions of the slab and the tubes as well as their reinforcements are selected based on design-loads at the order of magnitude of 1-0,5 ton/M². This is particularly for airport runways. Roads are according to present invention constructed with such great area that design-loads of the magnitude of 0,5 ton/m² are achieved. The problem of shrinkage can be solved with dummyjoints or with a cover layer. The present ground slab is laid on such soft ground that the machines can not )easily be supported by it. Therefor the soft ground is covered with a layer of sand and/or lean concrete.

The invention will be illucidated with reference to i drawing. The drawing shows in:

• Figure 1 a plan view of a ground plate according to the invention,
• Figure 2 on larger scale section II-II of Figure 1 concerning an airport runway,
• Figure 3 a section corresponding with Figure 2 concerning a road-construction,
• Figures 4 and 5 on larger scale two variants of a section over line IV-IV of Figure 2, and
• Figure 6 a load diagram.

The ground plate 1 comprises a slab 4 of concrete reinforced with reinforcements 5 and a plurality of tubes 3. The tubes 3 have a length h, a wall thickness e, a diameter f, a pitch distance g and reinforcements 6 which are embedded in the concrete 9 of the slab 4 for rigid connection of the tubes 3 to the lower side of the slab 4.

The ground plate 1 of Figure 1 has an area d x g which is so great that the maximum total weight resting thereon results in a ground load, which is less than the maximum permissible ground pressure of the soft ground. The dimensions of slab thickness c and the dimensions of the reinforcements 5 thereof as well as the dimensions of the tubes 3 and their reinforcements are selected based on design-loads of the order of magnitude of 1-0,5 ton/m².

In the airport runway construction of Figure 2 based on design-loads of 1 ton/m², c = 20 cm.,

• h = 200 cm.,
• e = 8 cm.,
• b = 120 cm., and
• a = 250 cm.

In Figure 2 a layer of sand 8 covers the soft soil 2. Lean concrete 7 covers the layer of sand 8.

In the road construction of Figure 3 based on design-loads of 0,5 ton/m², c = 10 cm.,

• h = 200 cm.,
• e = 8 cm.,
• b = 120 cm., and
• a = 350 cm.

In Figure 3 the soft soil 2 is covered with a thin Layer of subbase 10 and a thin layer of lean concrete 7.

The tubes 3 are only interconnected by the slab 4.

The invention concerns with the construction of highways, which are so permanent and so rigid in construction, that for a bus-station, for instance, the parkinglots and the bus-terminal foundation can be executed by applying the invention. Same can be said about runways, taxiways and aprons of airports, included the foundations for the terminal, godowns and hanggars.

The.dimensions of the concrete components as well as of the reinforcement are based on design-loads of 1 ton/m² for.airportrunways and -aprons and of 0,5 ton/m² for highways. Never before have such small design-loads been used for airport- and roadpavements. This is due to the ability of the invention to support cooperatively the load put on it.

The runway as well as the highway slab consists of one continuous reinforced concrete slab without any expansion joints in both direction (longitudinal and transversal), what is not the normal practice in the previous concrete pavements. This will give an extra convenience for driving on it.

The concrete pipes firmly attached underneath the slab will also prevent the upheaval of the slab in case of the presence of uplift forces. The slab is kept completely level.

Whereas the road pavement should be permanent and without or almost without maintenance, no shrinkage- and expansion-joints should be applied in the whole length of the pavement, which makes shrinkage and expansion by change of temperature possible.

This can be obtained in two ways:

• According to Fig. 4: Applying the so called dummy- joints 11 on the pavement on certain distances if the pave- ⁵ment be made of bare concrete.

According to Fig. 5: Applying a thin layer 12 of sand-asphalt or concrete-asphalt on the concrete pavement to make the shrinkage-cracks (if any) invisible and free from moisture.

For the expansion of the concrete pavement by temperature increase no special expansion-joints are needed, due to the fact that the expansion of the concrete slab will be prevented by the passive soil-pressure against the reinforced concrete pipes 3 under the slab 4.

To prevent cracks in the concrete road-pavement by Erost and thaw, the allowable calculated soil-pressure under the concrete slab should have at least the same value as the maximum frost pressure, namely 0,35 ton/m².

To prevent the harmfull effect of excessive water under the concrete slab caused by thaw or flood, the allowable calculated soil-pressure under the slab should not exceed 500 kg/m² or 0,5 ton/m² for highways and 1000 kg/m² or 1 ton /m² for airport runways.

Taking the very small design-load in consideration, it will be clear that the invention is very useful and economical to be applied on soft soil, where the conventional system will need expensive preparations for its application.

The load diagram of Figure 6 shows a vehicle with weight Q resulting in a ground counter pressure q on the slab 4 and side pressure on the tubes 3 for obtaining the required bending moments from the tubes 3 on the slab 4. The mutual relationship between dimensions of the slab 4 and tubes 3 is as follows:where

• a = distance between tubes in meters;
• b = the outer diameter of the tube in meters;
• h = height of pipe in meters; (pipe = tube)
• r = the specific weight of the soil;
• m = soil constant, dependent on the internal angle of frincrion;
• q = the ground counter-pressure in ton/m²;
• k = the safety coefficient, amounting between 1½ and 2.