The present invention relates to an apparatus and a meth¬ od for building a foundation, particularly a frost- resistant foundation, for uprights such as flagpoles, posts, pillars or the like or for making passages there¬ through e.g. for cables, tubes etc., said apparatus com¬ prising a drive-shaft equipped helical auger, said shaft being provided with a tubular body portion, the helical auger having a substantially larger diameter than the body portion.

At present, the upright foundations are generally built by digging a hole in the ground, by setting a concrete pipe in the hole and by casting grippers or a self- erectable assembly in the concrete pipe. This type of method is relatively tedious and, in addition, causes disturbances in the environment e.g. when the installa¬ tion is made on a lawn, due to the necessity of digging a sufficiently large erection hole. The passages are presently made by using e.g. percussion drilling, press¬ ure drilling as well as ramming. One drawback in these methods is a relatively high power demand of the equip¬ ment used therein.

An object of the invention is to provide a relatively simple and expedient method and apparatus for facilitat¬ ing the building of a foundation for uprights, said apparatus and method being also applicable for fixing various objects to the bottoms of waterways. Another object is to provide an apparatus and a method for making various passages e.g. for passing under traffic routes. In order to achieve these objects, an appa¬ ratus of the invention is characterized by what is set

forth in the characterizing clause of claim 1. On the other hand, methods of the invention are characterized by what is set forth in the characterizing clauses of claims 12 and 14.

The most important benefit offered by an apparatus and a method of the invention is that the tapered leading end of a body portion achieves the compaction of the earth material penetrated by a helical auger, thus providing an improved base for a foundation or a pass¬ age.

The invention will now be described with reference made to the accompanying drawings, in which:

fig. 1 shows a lateral and sectional view of one embodi¬ ment for an apparatus of the invention, and

fig. 2 is a plan view of the apparatus shown in fig. 1.

According to figs. 1 and 2, an apparatus of the inven¬ tion includes a helical auger 2 which is provided with a drive shaft 3. The drive shaft 3 carries a tubular body portion , which in the illustrated embodiment in- eludes two sections 4 and 4a. The end of a leading sec¬ tion 4a facing said helical auger 2 is provided with a conical section 5 tapering towards the helical auger 2, said tapered section achieving the compaction of a soil layer penetrated by the helical auger. The magnitude of a coning angle ζ > of tapered section 5 is suitably within the range of circa 25 - 50 and preferably circa 30 - 45 . The length of tapered section 5 is prefer- ^■ ably at least equal to the pitch of helical auger 2, whereby the volume of earth material compacted by taper¬ ed section is at least equal to that of earth material

displaced by helical auger 2 during a single rotation. In view of compaction purposes, said tapered section 5 is located between helical auger 2 and body section 4a, whereby the apex of tapered section 5 facing said helical auger 2 is preferably substantially level with the top edge of helical auger 2, e.g. as shown with dash-dot- lines in fig. 1 , the earth material being compacted substantially over the entire length of the apparatus. In view of effective compaction, the ratio of the ex¬ ternal diameter of tubular section 4a to that of the cylindrical section of drive shaft 3 is suitably within the range of circa 1,5 - 10:1, preferably circa 2 - 8:1.

The ratio of the diameter of helical auger 2 to the ex¬ ternal diameter of body section 4a is at least appr. 1,8:1. Normally, the ratio is within the range of appr. 2:1 - appr. 3:1. The upper limit depends primarily on the earth material and it can be multiple compared with the above-described values. On the other hand, the ratio between the diameter of helical auger 2 and that of drive shaft 3 at the plate section is at least circa 2,7:1, the optimum range being circa 10 - 12:1. The drive shaft 3 is further fitted with a flange element 7 which is set on top of a component 8 , the latter being fitted inside tubular section 4a and providing a bearing surface. The end 10 of drive shaft 3 facing body section 4a is pre¬ ferably designed to be square-shaped for rotating said drive shaft 3 with an appropriate wrench, adapted for working inside tube 4. The end 10 of drive shaft 3 facing body section 4a can also be provided with other types of gripping means for a driving device, such means including e.g. an Allen key hole, a threaded hole, a square hole etc., wherein a complementary-shaped tool can be fitted for rotating the drive shaft. inside the ends of body portion 4a and 4 coming against each other

is preferably provided a threaded section 9 which car¬ ries a threaded connecting sleeve 6 for fastening said body sections 4a and 4 removably to each other. In addition, the end of body portion 4 facing away from said leading section 4a can be provided with a corre¬ sponding threading for extending the body portion to include a plurality of sections.

The body portion 4a, 4 can also be designed as an integ¬ ral component, fixedly mounted on drive shaft 3, the apparatus thus being operated preferably by rotating the body portion.

The apparatus can also be designed e.g. in a -manner that the leading section 4a of a body portion is fixed¬ ly mounted on drive shaft 3 while the remaining section 4 is made e.g. of a thin-walled sheet metal pipe, a plastic tube or a like, which can be used as a tubular mould when building a foundation.

When using the apparatus for building a foundation for uprights, said drive shaft 3 is rotated by means of appropriate driving mechanisms to a desired depth and, if necessary, the apparatus length is increased by in¬ cluding more tubular sections 4 in the apparatus by means of connecting sleeves 6 or like fastening ele¬ ments. After reaching a desired depth, the driving mechanism can be removed or left in position, if desi¬ red. Thus, the apparatus can be used as a foundation as such, whereby a structure to be erected can be in¬ serted directly inside tubular section 4 or it can be filled e.g. with cast concrete for building a more stable foundation, in which case the top portion of a foundation is usually provided with separate fastening elements for fixing a structure to be erected.

When operating at relatively low depths, e.g. appr. 0,5 - 2,5 m, it is possible to use an embodiment in which the body portion forms an integral unit with shaft 3 , the apparatus being operable by rotating the body portion with appropriate mechanisms. This is well applicable e.g. to building foundations for fence posts.

In view of making a foundation frost-resistant, the upper portion of the apparatus can be provided e.g. with a suitable plate element which is tightened in position so as to produce tension in a soil layer be¬ tween helical auger 2 and a plate element. Generally, the freezing of earth produces a vacuum in the soil layer, said layer absorbing water from the deeper non- freezing layers. The above-described formation of tension in a soil layer prevents the absorption of water into said soil layer and, thus, the formation of so-called frost boils.

When using the apparatus for making passages, said drive shaft 3 is rotated with appropriate driving mechanisms until the apparatus comes into the sight e.g. on the other side of a road, if the question is about road underpasses. After the apparatus has come in sight on the opposite side, the apex section 4a can be removed in the illustrated embodiment and the re¬ maining body section 4 can be left as such to serve as a cable conduit.

In order to provide a passage for various tubes, cables and the like it is also possible to employ such an embodiment, wherein said drive shaft 3 is only fitted with a short apex section 4a of the body portion where¬ by, when operating in a suitable soil material, the

apparatus creates directly in the soil material a re¬ latively tight-surfaced duct for tubes, cables and the like. This embodiment is also useful in building foundations, the duct being filled e.g. with concrete and a drive-shaft operating means, e.g. a rod or a wire cable, is preferably left in position inside cast concrete.

The above-described embodiments are only intended to show examples of a few preferred designs and applica¬ tions for the apparatus and the method and there is no intention to limit the scope of protection defined in the annexed claims. The apparatus can be used e.g.. in place of a drilling pole and also as an achoring device and erection method in the soil layer of the bottom of waterways, even at the depths of several .hundred meters. In this context, it is essential that the installation can be effected from a vessel on the surf¬ ace or even from the surface of frozen ice, the helical auger overcoming the levating force caused by ice, whereby this application is excellent e.g. as a pier ost.

In the context of the present application it is used the term "helical auger" for the helical member 2. It should be noted that the helical member 2 is used mainly as a tool to pull th apparatus l into the ground as well as a load-bearing member and, therefore, the term helical auger could be replaced e.g. by one of the terms "helical blade, helical plate or helical flange" whichever is preferred.