GB2048983A

GB2048983A - Ground or Rock Anchor

Info

Publication number: GB2048983A
Application number: GB8005027A
Authority: GB
Original assignee: VISH MINNO GEOLOSHKI INST
Current assignee: VISH MINNO GEOLOSHKI INST
Priority date: 1979-02-20
Filing date: 1980-02-14
Publication date: 1980-12-17
Also published as: DE3004540C2; RO82092B; CS237953B1; RO82092A; FR2449779A1; ATA62980A; SU1063940A1; BG32663A1; FR2449779B1; AT370210B; GB2048983B; DE3004540A1; DD160886A3; PL221885A1; SE8000930L

Abstract

The invention provides a ground or rock anchor, which comprises a thin-walled tubular body 1 in the form of a pipe, a front portion 2 of which has a circular cross-section and a rear portion 3 of which has an oval-shaped cross-section, wherein the perimeters of both said portions are substantially equal. An anchor in accordance with the invention tends to maintain or even increase with time the degree of support it provides to surrounding rock or soil structures. <IMAGE>

Description

SPECIFICATION Ground or Rock Anchor This invention relates to a ground or rock anchor, which is capable of application in underground and surface constructions.

A mechanical anchor-bolt is known, which consists of an anchoring head which by an anchor-rod is connected to a bearing plate. The actions of this anchor are based on the frictional forces caused by the head's expansion in the hole and the bearing stress of the plate transmitted through the rod.

The main disadvantage of this type of mechanical anchor is that with the passage of time the clamping force decreases significantly, which leads to reduction of the support provided by the anchor and creates an opportunity for deformations to develop in the rocks around the anchor.

An anchoring device is also known, from US Pat. No. 3665719, which consists of a flat tubular element, built from inelastic material, where the tubular element is deformed along its entire length and is closed from one end, while at the other end there is mounted a valve for feeding a fluid under high pressure, after the structure has been installed into a hole or a crack, and as a result the tubular element expands and exerts significant side pressure, and thus increases the friction along the adjacent surfaces of the already broken rock structure.

The most significant disadvantage of this device is that it can only be applied for strengthening an already broken rock mass; another is the need for special materials for its production.

An objection of the present invention is to provide a pipe-type ground or rock anchor which has universal applicability and which will maintain or improve with time the strength given to the soil or rock and thus prevent the development of deformations in the ground or rock structure in which it is placed.

According to the present invention there is provided a ground or rock anchor, which comprises a thin-walled tubular body in the form of a pipe, a front portion of which has a circular cross-section and a rear portion of which has an oval-shaped cross-section, wherein the perimeters of both said portions are substantially equal.

Preferably, the rear portion constitutes a major proportion of the total length of the anchor. The front portion of the anchor can constitute 20% or less of the total length of the anchor. A smoothly curved intermediate zone can be present between the said front and rear portions of the anchor.

The advantages of the invention are as follows: with the passage of time the pipe anchor maintains or increases the support given to, e.g., surrounding rocks and thus prevents the development of deformations and disintegration of the rocks; it has strengthening ability along the total length of the anchor and as a result is universally applicable-in soft as well as in hard rocks; it is simple to make and inexpensive to produce.

The invention will now be illustrated in greater detail by reference to the accompanying drawings, which show a practical embodiment of the invention, and in which: Figure 1 represents a side view of the pipe anchor; Figure 2 is a cross-section along line A-A of Figure 1; and Figure 3 is a cross-section along line B-B of Figure 1.

The ground anchor consists of a thin-walled pipe-like tubular body 1, of which a front part 2 constituting about 10% of the overall length of the anchor is shaped as a guide with a circular cross-section, and a rear part 3 constituting about 90% of the overall length of the anchor has an oval-shaped cross-section having two mutually perpendicular axes; the perimeters of the front and the rear parts are equal to each other and, in use, are equal to the perimeter of the pre-formed anchoring hole. A smoothly curved zone 4 joins the front and rear portions 2 and 3. The body 1 can conveniently be formed of steel.The thickness of the wall 1 is determined as a function of the diameter of the anchoring hole and the length of the long axis of the oval cross-section, and is preferably as expressed by the following formula:

where B=the length of the long axis of the oval crosssection; D=the diameter of the anchoring hole, which is the same as the outside diameter of the front portion 2; A=the thickness of the tubular body's wall; k=a coefficient, determined by the physical and mechanical properties of the steel and the rocks, such that 0.005 < k < 0.05; and length of the pipe.

The device is used as follows: a hole is first of all drilled in the rocks which are to be supported.

The perimeter of this hole is equal to the perimeters of the front part 2 and the rear part 3 of the body 1. The pipe-like anchor is then inserted into the hole by conventional techniques, e.g. by hammering, pressure or vibrations, after which the oval-shaped rear part 3, as a result of the rock pressure, tends to take a shape identical to that of the front part 2.

Claims

1. A ground or rock anchor, which comprises a thin-walled tubular body in the form of a pipe a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Ground or Rock Anchor This invention relates to a ground or rock anchor, which is capable of application in underground and surface constructions. A mechanical anchor-bolt is known, which consists of an anchoring head which by an anchor-rod is connected to a bearing plate. The actions of this anchor are based on the frictional forces caused by the head's expansion in the hole and the bearing stress of the plate transmitted through the rod. The main disadvantage of this type of mechanical anchor is that with the passage of time the clamping force decreases significantly, which leads to reduction of the support provided by the anchor and creates an opportunity for deformations to develop in the rocks around the anchor. An anchoring device is also known, from US Pat. No. 3665719, which consists of a flat tubular element, built from inelastic material, where the tubular element is deformed along its entire length and is closed from one end, while at the other end there is mounted a valve for feeding a fluid under high pressure, after the structure has been installed into a hole or a crack, and as a result the tubular element expands and exerts significant side pressure, and thus increases the friction along the adjacent surfaces of the already broken rock structure. The most significant disadvantage of this device is that it can only be applied for strengthening an already broken rock mass; another is the need for special materials for its production. An objection of the present invention is to provide a pipe-type ground or rock anchor which has universal applicability and which will maintain or improve with time the strength given to the soil or rock and thus prevent the development of deformations in the ground or rock structure in which it is placed. According to the present invention there is provided a ground or rock anchor, which comprises a thin-walled tubular body in the form of a pipe, a front portion of which has a circular cross-section and a rear portion of which has an oval-shaped cross-section, wherein the perimeters of both said portions are substantially equal. Preferably, the rear portion constitutes a major proportion of the total length of the anchor. The front portion of the anchor can constitute 20% or less of the total length of the anchor. A smoothly curved intermediate zone can be present between the said front and rear portions of the anchor. The advantages of the invention are as follows: with the passage of time the pipe anchor maintains or increases the support given to, e.g., surrounding rocks and thus prevents the development of deformations and disintegration of the rocks; it has strengthening ability along the total length of the anchor and as a result is universally applicable-in soft as well as in hard rocks; it is simple to make and inexpensive to produce. The invention will now be illustrated in greater detail by reference to the accompanying drawings, which show a practical embodiment of the invention, and in which: Figure 1 represents a side view of the pipe anchor; Figure 2 is a cross-section along line A-A of Figure 1; and Figure 3 is a cross-section along line B-B of Figure 1. The ground anchor consists of a thin-walled pipe-like tubular body 1, of which a front part 2 constituting about 10% of the overall length of the anchor is shaped as a guide with a circular cross-section, and a rear part 3 constituting about 90% of the overall length of the anchor has an oval-shaped cross-section having two mutually perpendicular axes; the perimeters of the front and the rear parts are equal to each other and, in use, are equal to the perimeter of the pre-formed anchoring hole. A smoothly curved zone 4 joins the front and rear portions 2 and 3. The body 1 can conveniently be formed of steel.The thickness of the wall 1 is determined as a function of the diameter of the anchoring hole and the length of the long axis of the oval cross-section, and is preferably as expressed by the following formula: where B=the length of the long axis of the oval crosssection; D=the diameter of the anchoring hole, which is the same as the outside diameter of the front portion 2; A=the thickness of the tubular body's wall; k=a coefficient, determined by the physical and mechanical properties of the steel and the rocks, such that 0.005 < k < 0.05; and length of the pipe. The device is used as follows: a hole is first of all drilled in the rocks which are to be supported. The perimeter of this hole is equal to the perimeters of the front part 2 and the rear part 3 of the body 1. The pipe-like anchor is then inserted into the hole by conventional techniques, e.g. by hammering, pressure or vibrations, after which the oval-shaped rear part 3, as a result of the rock pressure, tends to take a shape identical to that of the front part 2. Claims

1. A ground or rock anchor, which comprises a thin-walled tubular body in the form of a pipe a front portion of which has a circular cross-section and a rear portion of which has an oval-shaped cross-section; wherein the perimeters of both said portions are substantially equal.

2. An anchor as claimed in claim 1 , wherein the said front and rear portions are joined by a smoothly curved zone.

3. An anchor as claimed in claim 1 or 2, wherein the said rear portion constitutes a major proportion of the total length of the anchor.

4. An anchor as claimed in claim 1, 2 or 3, wherein the said front portion constitutes not more than 20% of the total length of the anchor.

5. An anchor as claimed in claim 1, 2, 3 or 4, wherein the body is formed of steel.

6. An anchor as claimed in any preceding claim, wherein the thickness of the wall of the tubular body satisfies the relationship:

where 0.005 < kA0.05, and the other parameters have the meanings given hereinbefore.

7. A ground or rock anchor substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawing.