DE2062081A1 - Methods of controlling the safety of mining cavities - Google Patents

Description

DR.-ING, DIPL.-ING. M. SC. D.PL .-. 'HVS. DR. DIPL.-PHYS.

HOGER-STELLCHT-GRIESSBACH-HAECKER

A 38 536 h
. t-35
December 14, 1970

l7.S-.Ser.No. 886,911

Shosei Serata
14 Calvin Court, Orinda, Contra Costa, California / USA

Methods of controlling the safety of mining cavities

The invention relates to a method for controlling the long-term security of underground cavities against collapse.

In various applications it is desirable to create underground cavities that are safe against collapse for a longer period of time without extensive additional supporting structures, e.g. when mining ore deposits surrounded by broken or fissured rock, the usual mining methods of economical -

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impose severe restrictions on the ability and safety of ore mining. For this reason, the path has often been chosen, the width of the cavities small - often less than that Two to three times the cavity height - and the strength of the supporting pillars left in the cavities large - often more than ten times the cavity height - to be selected to avoid the possibility of the ceiling structure collapsing for safety reasons to reduce. If a reduction in the cavity width and an increase in the strength of the supporting piers are not sufficient, in order to ensure long-term safety of the mining cavities is generally a more extensive one Extension of the route required. These safety measures naturally reduce the profitability of ore mining, and not only because of the cost of the supporting structures and their maintenance, but also because of the reduced utilization of the Ore reserves and because of the limited space that prevents the economic use of rapid mechanical mining methods.

As an alternative to such dismantling methods with extension or support pillars, a dismantling method has been developed that variously with "long front-like dismantling", "full dismantling" or "Bruchbau" is called. The essence of this method is that after the ore has been extracted, the roof closes according to plan Fracture is thrown, the fracture being slow and uniform. To regulate the speed of this process when dismantling from the boundary of a construction section to the shaft, only small supporting pillars are left behind, which only need to be designed in such a way that man and machine are always in a safety zone in front of the advancing Fracture. Although the demolition method has the advantage of relatively large cavity widths and small supporting pillar strengths and therefore

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with a high funding ratio, it is from the standpoint of long-term support from heavy loads disadvantageous. This method is therefore useless for mines under construction where such a controlled one Support is essential. This method cannot be used, for example, even if the hanging wall or lying water leads, as a considerable damage of the ridge or, the sole a flooding of the Mine can cause.

The dismantling method has recently been modified so that dismantling is limited to limited areas and through large ones Support pillars were blocked, the thickness of which was often ten times the height of the cavity. This so-called blocked dismantling Although it provides support for heavy loads, it cannot guarantee long-term safety, as all these cavities eventually collapse. The modified one Dismantling still has the disadvantage that it has full control of heavy loads and the safety of the Working area is missing. Especially for those under construction For this and many other reasons, mines are preferred to demolition.

According to the current state of the art, no method is known that can also be used in mines under construction weak roof structure guarantees safe mining cavities against collapse, except for those in which the Cavity width and the delivery rate despite additional supporting structures has the relatively low permissible value. This increases the profitability of ore mining considerably limited. Furthermore, in the known excavation methods, the production of mining cavities or tunnels

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for other purposes of great width only possible with extremely expensive supporting structures.

The invention is now based on the object of a method for controlling the safety of mining cavities of the type mentioned to create, which can be interpreted for any desired period and also with usable and fissured mountains, which are subject to high rock pressures, can be used without requiring additional supporting structures, and which for safety reasons for the mine and for structures on the surface of the surface the amount of a change in shape or subsidence of the ground above a mined deposit is able to influence.

This is achieved according to the invention in that initially on both sides an area of the mountain in which a protected cavity is to be created later, two relief cavities with these surrounding primary stress envelopes are formed, that then in the area between the two relief cavities the protected cavity forming intermediate pillars between the relief cavities and the protected cavity is created and that the strength of the intermediate pillars is chosen so that they do not break able to yield to the rock pressure so far that the primary stress envelopes around the two relief cavities and if necessary one around the protected cavity relatively quickly into a common, both the relief cavities and the secondary stress envelope surrounding the protected cavity pass over, which the horizontal and vertical rock pressure around the protected cavity permanently absorbs and in the mountains surrounded by it Forms a relaxation zone that protects against fissures 4es mountain range on the inner boundary surfaces of the secondary Spännungshtille offers.

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December 15, 1970.

The intensity of the tension field in the mountain in which the protected cavity is to be created, is thus through the controlled formation of tension sheaths on a portable Reduced value, for a freely selectable Period, so also for all the time.

For the controllable formation of the primary voltage envelopes around the Relief cavities are, according to one embodiment of the invention, a predetermined breaking of the ridge and possibly Sole of the relief cavities, so a lowering of the hanging wall and possibly a swelling of the lying, with respect to the Allow time delay until the protected cavity is formed. It is advantageous if this is predetermined Collapse is made possible that depending on the rock mechanisehen Characteristics of the mountain range a predetermined width of the relief cavities as well as the protected cavity with respect to their amount is chosen.

The thickness of the intermediate pillars is advantageously chosen so that they are able to yield to such an extent that the entire primary tension envelope around the relief cavities and, if necessary, around the protected cavity merge into a common secondary tension envelope surrounding both the relief cavities and the protected cavity, and yet that able to provide sufficient support for relaxed mountains immediately above the protected cavity.

According to a further embodiment of the invention, at least one of the relief cavities - and preferably also the protected cavity - is formed from a number of adjacent and optionally substantially parallel partial cavities which have relatively thin partial walls between them. Despite the partial walls, a single primary stress envelope is formed around the relief cavity, provided that the cutting of the partial cavities proceeds from one side to the other. the

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Partial walls are chosen so thin that they only have a temporary effect while working in the relief cavities Provide protection against crumbling of the broken hanging wall and the state of tension around the relief cavities not change around. Partial walls in the protected cavity can facilitate weather management. To delay a breakdown of the protected space they are not required in the method according to the invention.

The time span of the safety of mining cavities, i.e. the time until cracks and plastic deformations occur The time it takes for the cavity to become unusable depends on the nature of the rock mechanical impairment that is to be expected in the protected rooms. The safety period is thus primarily through the rock mechanical state of the rock and the intended Use of the protected cavities intended. Routes for the main traffic of a mine can for example be for a safety period can be designed which is at least as long as the expected service life of the mine.

The safety period of a protected mining cavity can be predetermined at any time by changing the five construction parameters, width of the relief cavities, width of the protected space, thickness of the intermediate pillars, time delay until the protected cavity is formed and the number of partial cavities or subspaces. Another possibility to influence the safety period is to introduce a geometric factor of the intensity of the relief cavities, ie the ratio of the total width of the relief cavities to the total width of the protected space. The intensity of the relief cavities can be varied in a range that depends on the rock-mechanical state of the rock. The bigger

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this factor is, the greater is the for given values five basic parameters the safety period. Through systematic Modification of the five basic parameters mentioned and one geometric factor can be protected mining Cavities can be designed for any safety period from less than a month to:. An infinite period of time. This is true for most mountain mechanical states except if there is no mountain immediately above the protected cavity sufficiently coherent, such as loose sand, flowing clay or very thin layers of fissured Rock.

According to another embodiment of the invention, the process of transferring two primary tension sheaths into a stable one can be performed secondary tension envelope - if necessary several times - are repeated in that between two previously formed secondary tension envelopes, each having two relief cavities and surround a protected cavity, another

art

it protects the cavity that is formed so that the secondary tension envelopes merge into a tertiary tension envelope. Which surrounds the two secondary tension envelopes and the further protected cavity. ^c

The process of transferring these tension sheaths can be multiple be repeated to create a large stable stress envelope that completely or partially covers a mined deposit enveloped. The shape and the height of this resulting stable tension envelope can be selected with the method according to the invention that the tension envelope can be accommodated in any formation of the mountain range that is suitable, to keep the tension envelope stable.

For securing the mine and structures on the surface several elongated tension envelopes with supporting pillars in between can be arranged parallel to one another.

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net in order to control deformation and settling of the hanging wall to form a protective layer of stable tension shells. Such control enables one Safe mining of a maximum deposit area without disturbing the mountains beyond a predetermined value. this is particularly important if the layers above the area to be protected contain groundwater.

In the following, the invention will be described with reference to some of the appended Drawing illustrated embodiments explained in more detail. Show it:

Fig. 1 is a schematic representation of a conventional mining Cavity and the associated stress envelope with superimposed transverse stress distribution in the median line of the cavity,

FIG. 2 shows a representation similar to that of FIG. 1 with the first stages of an embodiment of the method according to the invention,

3 and 4 are schematic representations similar to that of FIG. 2 with the following stages of the process,

5 shows a schematic representation of the last stage of the process,

Fig. 6 is a view similar to that of Fig. 2 showing a modification of the method according to the invention with a number of partial cavities which form the relief cavities,

FIG. 7 is a view similar to that of FIG. 5, showing a modification of the method according to the invention shows a number of subspaces which form the protected cavity, and

8 shows a further view similar to that according to Pia, S, which shows the process of transferring tension envelopes.

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If, as shown in FIG. 1, a mining cavity 11 underground, for example a horizontally running excavation or rock section, is excavated or otherwise excavated, a stress envelope 12 is formed around the cross section of the cavity substantially uniformly. The Spannungshiille represents the voltage zone at a the starting voltage with respect to the boundaries of the cavity exceeding tangential Oq. The cross-voltage <O, the tangential <OQ ie in the roof in the perpendicular bisector of the cavity, the curve 13 is distributed generally in accordance with. As can be seen from this curve, the stress is strongly concentrated immediately adjacent to the cavity 11. What is more important, however, is that the stress gradient there is extremely steep. Investigations have shown that it is not the gravitational forces, but this concentration and this large gradient of the transverse stress in such a conventionally shaped cavity 11 that are directly responsible for the process of the ceiling breaking. In order to keep the possibility of the ceiling collapsing small, it has hitherto been customary to limit the width of the cavity and / or to erect expensive supporting structures. Both of these measures are undesirable from an economic point of view, and in some cases even insufficient, for the reasons mentioned above. The present invention eliminates these difficulties by providing a manufacturing method for a pit construction in which stress-relieving cavities and protected piles are formed close together, so that a Schutzspanmmgnhüllg is controllably formed, which includes the pit and serves to provide long-term safety for any desired period of time of the mined cavity against fissuring or collapsing of the surrounding mountains without the need for auxiliary support structures.

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With reference to the illustrated embodiments, the construction method according to the invention will be described in somewhat more detail. The method generally consists in first carving out at least two relief cavities in the rock in which one or more protected cavities are to be formed later, and that then the degree of Collapse of the ridge and sole of the relief cavities is chosen so that there is one around each relief cavity primary tension envelope forms controllable, and that then finally one or more protected cavities in the Area between two previously formed relief cavities with the formation of intermediate pillars, their strength is chosen so that they are able to yield easily and thereby the individual, to the relief cavities and the transform the primary tension envelope belonging to protected cavities relatively quickly into a single secondary tension envelope, which comprise the mine construction consisting of the relief cavities and the protected cavities. The secondary The tension envelope has a tension-free zone in its interior and is used without auxiliary support structures to support the hanging wall stably and to absorb the rock pressure around the protected cavities, while the stress-free Zone acts as a stable shell, which offers protection against rock detachment on the inner boundary surfaces of the secondary stress shell.

The first embodiment of the method according to the invention is shown in FIGS. First are two Relief cavities 14 and 16 have been carved out or otherwise formed, for example as stretching horizontally run through the mountains. The relief cavities are parallel to each other and at a distance from each other on the both sides of a horizontally extending area 17,

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in which later a protected cavity with a predetermined Safety period should be created.

As a result of the relief cavities, primary stress envelopes 18 and 19 are formed around them. First are the primary tension shells 18 and 19 relatively flat and the tangential stress <5 "q, as indicated by the peak in the transverse stress distribution curve 21 of Fig. 2, concentrated in a relatively narrow stress zone around each relief cavity. The ridge 22 and the sole 23 of each relief cavity are chosen so wide that they after a predetermined period of time Able to give way in a predetermined way in order to relax the hanging wall and the lying of the cavities.

After a certain time, the ridge and sole have broken down to the extent shown in FIG. 3. The primary stress envelopes bulge outwards, as a result of which, as can be seen from the transverse stress distribution curve 21, the The peak value of the tangential stress is reduced and at the same time the strength of the stress envelope is increased. This is the Excessive tangential stress over a wider and deeper stress zone in the vicinity of the relief cavities distributed. The relaxation can be allowed to such an extent that the ridge of the relief cavities breaks off and, as at 24 indicated in Fig. 4, falls on the sole of the relief cavities, whereby a stable natural ridge is newly formed. This causes a further flattening of the peak value of the transverse stress distribution curve and an even greater expansion the tension envelope.

In the foregoing it is important that the formation of the primary stress envelope around the relief cavities through the choice of the degree of extension of the ridge and sole of the

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December 15, 1970

Relief cavities is controllable. The degree of collapse can be determined taking into account the mechanical condition of the rock of the surrounding mountains by choosing the width of the relief openings in relation to their height and that of the Width of the intended protected cavity can be determined. The larger the width of the relief cavities, the more faster and deeper the relaxation of the hanging wall and the recumbent takes place and the higher is therefore according to a given The primary tension envelope. The degree of breakage of the ridge and sole can therefore be chosen as desired between a slight reduction in tension in the mountains and a complete breakdown in order to restore the training control the primary tension envelope to any desired extent.

Subsequent to the formation of the primary tension envelopes and 19 in the manner described, as shown in FIG. 5, In the area 17 between the relief cavities 14 and 16, the intended protected cavity 26 is carved out or otherwise formed. The created in this way between the protected cavity and the relief cavities Intermediate pillars 27 are dimensioned in such a way that they can yield to the rock pressure without collapsing in order to prevent further deformation of the surrounding mountains. For this purpose, the intermediate pillars 27, depending on the flexibility of their Materials in relation to the mountain pressure, made narrow. By yielding the intermediate pillars 27, the primary tension envelopes, i.e. tension envelopes 18 and 19 of relief cavities 14 and 16 and one not shown here primary tension envelope around the protected cavity 26, transferred into a single secondary tension envelope 28, which includes the mine construction consisting of the relief cavities and the protected cavity and the entire mountain range in relaxes its interior and thus creates a tubular relaxation zone 29.

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The secondary tension envelope 28 has on the whole an oval or laterally elongated, elliptical shape that extends above and below the protected cavity from the relief cavities extends from arcuately inward. The associated distribution of the transverse stress' o'- in the mid-perpendicular of the protected cavity 26 is represented by curve 32. The curve points away from the protected cavity perpendicular to the outside, a maximum corresponding to the secondary tension envelope 28, which towards the inside becomes a relatively flat one and only slightly curved minimum passes over, which corresponds to the relaxation zone 29 of the tension envelope.

As can be seen from curve 32, the stress gradient in the relief zone 29 is relatively flat and thus small in comparison those of the voltage distribution curve 13 according to FIG. 1. As a result the protected cavity 26 is protected against pressures of the overburden and the side rock and by the high Concentration of the tangential stress in the protected area The cavity surrounding the secondary tension envelope almost permanent kept stable. As a result of the tubular relief zone 29 occurs in the cavity immediately adjacent to the protected cavity Mountains hardly show a concentration of stress, which means that the relaxed mountains act as a cylindrical shield, which counteracts the normally expected fissures of the rock on the inner boundary surfaces of the stress envelope. Furthermore, the intermediate pillars 27 serve in the entire hanging wall and lying within the tension envelope to prevent the build-up of stresses due to creeping deformation of the intermediate pillars. Simultaneously causes the remaining Strength of the yielding intermediate pillars sufficient support for the relaxed mountains immediately above of the protected cavity.

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The safety period of the protected cavity 26 of the mine structure according to FIG. 5 can be determined by the choice of its basic parameters are controlled: width of the relief cavities 14 and 16, width of the protected cavity 26, thickness of the Intermediate pillar 27, time of formation of the protected cavity and number of sub-cavities and sub-spaces, respectively depending on the rock-mechanical state of the surrounding rock.

In the embodiment described with reference to FIGS. 2 to 5, there are both the relief cavities and the protected cavity from a single opening. Both can, however, as shown in FIGS. 6 and 7, partial cavities and have subspaces. The respective widths of these spaces determine the extent of the primary stress envelopes (Fig. 6), and the time delay before the protected cavity is formed determines the degree of tension in the rock within the primary tension envelope. The width of the protected cavity affects the shape and size of the secondary stress envelope, and the thickness of the intermediate pillars determines the speed with which the primary tension envelope merge into the only secondary tension envelope 28. By providence the width of several partial cavities and partial spaces can be greater than in the case of only one opening in each case. The rock mechanical The condition of the rock is determined by three basic factors: the initial stress field underground, rock properties and the shape of the intended openings in the mine.

The concentration of the tension in the secondary tension envelope 28 and thus its strength as well as the envelope of the relaxation zone 29 are determined by the extent to which in the formation of the protected cavity 26 the controlled Formation of the primary tension envelopes 18 and 19 advanced

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is stepped. In this way, the protected cavity 26 is created by the controlled formation of the secondary tension envelope and the relief zone by means of the described selection of the five basic parameters even in rough and fissured mountains protected for any desired safety period. A mine with a protected one formed in the manner described Space is suitable for use as the main access to a pit or for another mining cavity, which guarantees safe underground traffic for its entire life without maintenance work on its ridge target. .

In Fig. 6 is a second embodiment for the provision of relief cavities 84 and 86, which correspond as a whole to the relief cavities 14 and 16 of FIG. In this arrangement, too, the relief openings are arranged on both sides of an area 87, in which the protected cavity is to be formed. The relief cavities consist of a number of partial cavities, with partial cavities 88 and 89 being the relief cavity 84 and partial cavities 90, 91 and 92 being the relief cavity 86 form. Thin partial walls 93 are located between the partial cavities. Forms regardless of the number of these partial cavities only one primary stress envelope 94 or 95 around the corresponding relief cavities 84 and 86 at a time.

The relief cavities described from several sub-cavities can be used in a single protected cavity according to FIG. 5 or ^4, however, as can be seen from FIG are separated from each other. Here, too, the two primary tension envelopes of the two relaxation cavities go into a single one

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secondary stress envelope 100 over which all stress relief cavities and comprises the protected cavity.

The act of moving two primary tension envelopes, e.g. 18 and 19, into a stable secondary tension envelope, e.g. 28, can be repeated with two such secondary tension envelopes to form a stable tertiary tension envelope which includes all of the affected relief cavities and protected cavities as shown in FIG. A protected cavity 26 'is shown there, which is arranged between two secondary tension envelopes 28' and 28 ″ which are arranged at a distance from one another. These secondary tension envelopes form a stable tertiary tension envelope 110. A Such a combination of tension envelopes can be multiple be repeated by pairs of last generated voltage envelopes to form a fourth stable. Tension sleeve 112 be used.

In the foregoing, the invention has been described with reference to the construction of horizontally extending, level routes. The method according to the invention can, however, also be used in an equally advantageous manner in the case of inclined stretches, namely independently of their angle of inclination, as well as for three-dimensional mining cavities underground.

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Claims (8)

A 38 536 h - 1? - Patent claims: 1. Process for controlling the long-term security of mining cavities underground against collapsing, characterized in that initially on both sides of an area (17) of the rock, in which a slotted cavity (26) will later be created two relief cavities (14, 16) are to be formed with primary stress envelopes (18, 19) surrounding them, that then in the area (17) between the two relief cavities (14, 16) the protected cavity (26) forming intermediate pillars (27) between the relief cavities (14, 16) and the protected cavity (26) is created, and that the strength of the intermediate pillars (27) is chosen such that they break without breaking Able to yield to the rock pressure so far that the primary stress envelopes (18, 19) around the two relief cavities (14, 16) and possibly one around the protected cavity (26) relatively quickly into a common, a secondary tension envelope surrounding both the relief cavities (14, 16) and the protected cavity (26) (28), which permanently reduces the horizontal and vertical rock pressure around the protected cavity (26) , and in the mountains it encompasses a relaxation zone (29), which provides protection against fissures in the rock on the inner boundary surfaces of the secondary Tension sheath (28) offers. - 18 - 109 830/1195 A 38 536 h - 18 - 2. The method according to claim 1, characterized that for controllably forming the primary tension envelopes (18, 19) around the relief cavities (14, 16) a predetermined breaking of the ridge and possibly Sole of the relief cavities (14, 16) with respect to the time delay until the protected Cavity (26) is made possible. 3. The method according to claim 2, characterized in that to enable a predetermined Breaking of the ridge and possibly the sole of the relief cavities (14, 16) a predetermined width depending on the rock mechanical properties of the rock the relief cavities (14, 16) and the protected cavity (26) is selected with regard to their height, 4. The method according to claim 1, 2 or 3, characterized in that the thickness of the intermediate pillars (27) is chosen in such a way that these are able to yield so far that the entire primary stress envelopes (18, 19) around the relief cavities (14, 16) and optionally around the protected cavity (26) in a common, a secondary tension envelope surrounding both the relief cavities (14, 16) and the protected cavity (26) (28) pass over and yet the relaxed mountains sufficiently close immediately above the protected cavity (26) support ability. 5. The method according to any one of claims 1 to 4, d. characterized in that at least one of the relief cavities (84, 86) is formed from a number of adjacent and optionally substantially parallel partial cavities (88 _# 89; 90, 91, 92), - 19 - 10 9 8 3 (1/1195 A 38 536 h - 19 - which have relatively thin partial walls (93) between them (Fig. 6). . . 6. The method according to claim 5, characterized that both relief cavities (84, 86) from a number of partial cavities (88, 89; 90, 91, 92) are formed. 7. The method according to any one of claims 1 to 6, characterized marked that the protected cavity (96) from a number of adjacent and optionally substantially parallel partial spaces (97, 98) is formed, the relatively thin partial walls between them have (Fig. 7). ' 8. The method according to any one of claims 1 to 7, characterized in that between two previously formed secondary tension ^{sheaths (28 1} , 28 "), each surrounding two relief cavities and a protected cavity, a further protected cavity (26 ') is formed in this way that the secondary tension envelopes (28 ¹ , 28 ") merge into a tertiary tension envelope (110) which surrounds the two secondary tension envelopes (28 ', 28") and the further protected cavity (26') (FIG. 8). 10983 0/1 1 9 5