15.6 Ответь на вопросы:

1. This can cause problems to the structure the foundation is supporting.

What does the pronoun this refer to?

2. is not loaded beyond its bearing capacity

What does the pronoun its refer to?

3. Other design considerations include

What does the adjective other refer to?

4. This swelling can vary across the footing due to seasonal changes

What does the demonstrative adjective this refer to?

5. cracking the structure over it.

What does the pronoun it refer to?

6. Raft slabs with inherent stiffness have been developed in Australia with capabilities to resist this movement.

What does the demonstrative adjective this refer to?

15.7 Прочитай, переведи текст foundations of residential and industrial buildings и расположи абзацы в правильной последовательности:

1. A foundation is a structure that transfers loads to the earth. Foundations are generally broken into two categories: shallow foundations and deep foundations.

2. A deep foundation is used to transfer a load from a structure through an upper weak layer of soil to a stronger deeper layer of soil.

3. A shallow foundation is usually embedded a meter or so into soil. One common type is the spread footing which consists of pads of concrete or other materials which extend below the frost line and transfer the weight from walls and columns to the soil or bedrock. Another common type is the slab-on-grade foundation where the weight of the building is transferred to the soil through a concrete slab placed at the surface.

4. There are different types of deep foundations including helical piles, impact driven piles, caissons, piers, and earth stabilized columns. The naming conventions for different types of foundations vary among different engineers. Historically, piles were wood, later steel, reinforced concrete, and pre-tensioned concrete.

5. Other design considerations include scour and frost heave. Scour is when flowing water removes supporting soil from around a foundation (like a pier supporting a bridge over a river). Frost heave occurs when water in the ground freezes to form ice lenses.

6. Foundations are designed to have an adequate load capacity with limited settlement by a geotechnical engineer, and the foundation itself is designed structurally by a structural engineer.

7. The primary design concerns are settlement and bearing Shallow foundations of a capacity. When considering house versus the deep settlement, total settlement and foundations of a skyscraper differential settlement are normally considered. Differential settlement is when one part of a foundation settles more than another part. This can cause problems to the structure the foundation is supporting. It is necessary that a foundation is not loaded beyond its bearing capacity or the foundation will fail.

8. Changes in soil moisture can cause expansive clay to swell and shrink. This swelling can vary across the footing due to seasonal changes or the effects of vegetation removing moisture. The variation in swell can cause the soil to distort, cracking the structure over it. This is a particular problem for house footings in semi-arid climates such as South Australia, Southwestern US, Turkey, Israel, Iran and South Africa where wet winters are followed by hot dry summers. Raft slabs with inherent stiffness have been developed in Australia with capabilities to resist this movement. When structures are built in areas of permafrost, special consideration must be given to the thermal effect the structure will have on the permafrost. Generally, the structure is designed in a way that tries to prevent the permafrost from melting.

9. A bearing pile is a device to transmit the load of the building through a layer of soil too weak to take the load to a stronger layer of soil some distance underground; the pile acts as a column to carry the load down to the bearing stratum. Solid bearing piles were originally made of timber, which is rare today; more commonly they are made of precast concrete, and sometimes steel H-piles are used. The pile length may be a maximum of about 60 metres but is usually much less. The piles are put in place by driving them into the ground with large mechanical hammers. Hollow steel pipes are also driven, and the interiors are excavated and filled with concrete to form bearing piles; sometimes the pipe is withdrawn as the concrete is poured.

10. The foundations in residential and industrial buildings support considerably heavy loads. Floor loadings range from 450 to 1,500 kilograms per square metre, and the full range of foundation types is used for them. Spread footings are used, as are pile foundations, which are of two types, bearing and friction.

11. When the soil is so soft that even friction piles will not support the building load, the final option is the use of a floating foundation, making the building like a boat that obeys Archimedes’ principle — it is buoyed up by the weight of the earth displaced in creating the foundation. Floating foundations consist of flat reinforced concrete slabs or mats or of reinforced concrete tubs with walls turned up around the edge of the mat to create a larger volume.

12. An alternative to the bearing pile is the caisson. A round hole is dug to a bearing stratum with a drilling machine and temporarily supported by a steel cylindrical shell. The hole is then filled with concrete poured around a cage of reinforcing bars; and the steel shell may or may not be left in place, depending on the surrounding soil. The diameter of caissons varies from one to three metres. The friction pile of wood or concrete is driven into soft soil where there is no harder stratum for bearing beneath the site. The building load is supported by the surface friction between the pile and the soil.

13. Deeper foundation walls can also be built by the slurry wall method, in which a linear series of closely spaced caisson-like holes are successively drilled, filled with concrete, and allowed to harden; the spaces between are excavated by special clamshell buckets and also filled with concrete. During the excavation and drilling operations the holes are filled with a high-density liquid slurry which braces the excavation against collapse but still permits extraction of excavated material. Finally, the basement is dug adjoining the wall, and the wall is braced against earth pressure.

14. If these buildings do not have basements in cold climates, insulated concrete or masonry frost walls are placed under all exterior nonbearing walls to keep frost from under the floor slabs. Reinforced concrete foundation walls for basements must be carefully braced to resist lateral earth pressures. These walls may be built in excavations, poured into wooden forms. Sometimes a wall is created hy driving interlocking steel sheet piling into the ground, excavating on the basement side, and pouring a concrete wall against it.