自然资源部岩岩溶动力学重点实验室

IGCP 299 WORKING GROUP MEETING

1995-07-10KDL 1638

II1  IGCP 299 WORKING GROUP MEETING

IN BEIJING,CHINA,AUGUST,1993

Brian Finlayson

With regard to the publication for this project those at the meeting were agreed that we should write to each of the contributing national groups and get them to organize an author (or group of authors) and to select one particular karst area from each country to be featured in a chapter of about 6,000 words. The chapter would be expected to focus on the controlling characteristics of karst landscape development in that area. For example, if the Australians chose the Nullarbor, the dominant controlling characteristic would be aridity in the climate. This seems to me to be an achievable project in the time available and fulfils the aims of the IGCP Project.

For future developments, a concentration on the carbon cycle was agreed by all present to b e the best way to go. The details of this would require some consideration but given the current scenarios for global climate change there is some potential for significant changes to occur in the carbon cycle. A better understanding of the sources and sinks of carbon on the global scale and the role of carbonate rocks in this must be an important issue at this time. What do you think?

The meeting was attended by Roberto Domech from Cuba. He says that he has written to you regarding the involvement of Cuba in the IGCP 299. He asked me if I would contact you and ask you to add his name to the mailing list.

 

II2 IGCP 299 WORKING GROUP MEETING

IN SHIRAZ, IRAN, OCT., 1993

Ye Guijun

The meeting took place on Oct.26, 1993 after the symposium. Ye Guijun and E.Raeissie(Shiraz University) chaired the meeting. 41 people were at the event, among them were the newly elected UIS president Prof. Paolo Forti, Prof. W.Dreybrodt from Bremen University, Germany, Prof. Gultekin Gunay, the director of International Center for Karst Water Resources Research Center, Turkey, and Dr. Afrasiabain, Secretary General of the symposium.

Ye Guijun gave a talk on behalf of Yuan Daoxian, the leader of IGCP 299. He briefed the development of the Project in 1992, particularly the results of three excursions in Russia, USA, and Australia. The IGCP 299 Newsletter 1993 were given to all the participants.

Many Iranian colleagues were interested to participate the Project. Their name and address were sent to IGCP 299 Secretariat to be included in the mailing list. Somebody made inquiry about the training course of the Project, or the Institute of Karst Geology in Guilin.

 

II3 THE FIELD EXCURSIONS OF THE PERMIAN SYMPOSIUM

(URAL AREA RUSSIA 1992)

V.N.Andreytchuk

The symposium "Karst Engineering Geology" took place on August 2-8 in Perm. This City was selected for the symposium not by accident. There are much limestone, gypsum and salt karst in the environs of Perm. At Perm University and at Kungur karst station many karstologists work.

The karst of Perm area is very interesting in different aspects: geological, hydrogeological, paleogeographical, climatological etc. For excursions some places were selected where karst is peculiar and it had not been well lighted in the science literature (except the Kungur Ice Cave). The programme of excursion consisted of two parts: The Northern part (salt karst) and the Southern part (gypsum karst) (Fig.1).

NORTH EXCURSION

It took place in Berezniki area (Verknekamsky potassium basin). Here, on the depth of 100-450 m below the surface the salt thickness (P1) lies which consists of some potassium salt strata. There are 8 mines in the area where it is extracted on the surface. We have not salt karst forms in the landscape here except some depressions which formed by subsidence of the rock above the tops of salt body. These depressions are filled by water and they are very shallow. In this area the taiga woodland stretches. Two objects of salt karst were shown: the large collapse sink above the mine and salt spoil heap karst.

1.The largest collapse sink

It was happened in July 1986. The collapse sink formation took place above the mine field of Mine 8. It is interesting that the mines are located in this point deeper (420 m) than in some other places. The specialists thought that this mine is the safest place in the deposit area. But as a result of confluence of the circumstances the sole collapse has emerged just here.

Fig.1 The Urals and the site of symposium excursion
(1-The Northen Excursion, 2-The Southen Excursion)

The formation of collapse sink is connected with artificial and natural reasons. At the beginning of the 1980s the mining system was changed so that to increase the extraction of salt. The stiff ceiling system of mines had given the way to soft columns system. However, the soft salt columns, which are keeping the ceiling, crush little by little. In this process the salt ceiling is sagging and many cracks are growing up. They penetrate into salt thickness up till 50 m. The calculations have indicated that it was not dangerous because the thickness of the salt deposits above the mines reached 80-100 m. But it was not took into account the possible tectonic deformations and fault zones inside salt rocks. The cracks formation has gone along one of the fault zones and they have reached the top of the salt body. Brines began to penetrate into salt down. During January and February 1986 the output of brines was growing from 20 up to 150 m3 per hour. As a result of the filtration of brines, the brine aquifer about salt body was drained. Fresh waters from the overlying aquifers move down onto the salt. In the process of salt dissolution they formed vertical channels which uninterruptedly increased. When output of water had reached the catastrophic state (2000 m3 per hour) people had to leave the mine. Since this moment (March 8) the flood of mine space (15 millions m3) and formation of the cavity was beginning.

Till the middle of April the whole mine space was filled by water. In the salt layer the cavity about 1.5 millions m3 in volume had been developed. As a result of coming down of the rock material the ceiling of the cavity began to grow up and the cavity became to be filled with water and the falling deposits. Till the middle of July the cavity was under surface but on July 26 at night the collapsed took place. There was much noise and light when the collapse happened because gases that filled the cavity had been ignited. The inflammable gases inside the cavity were generated in the process of salt dissolution.

Some specialists thought that the explosion was the reason for the collapse but it was proved that the explosion was a consequence of the collapse. The gases took fire as a result of the clash between the falling stones and metallic tubes from the borehole, which was situated in the collapse place.

Originally the collapse sink was 40-80 m in diameter and 140 m in depth (Fig.2). After that it began to be filled up by water and different materials from the walls. In the present time the water level is located 40 m below the surface. The upper part of the sink became wider (100-150 m). The depth of the sink had been diminished up to 55-70 m. The water level had been stabilized and water mineralization had descended from 1g per liter to 0.4-0.5 g. Hydrodynamically, the sink became a window on the way of underground waters movement to the Kama River.

The Collapse sink had provoked a great scientific and practical interest of specialists. Since 1987 they carry out different observations in the sink and in the area. Interesting data and results had been obtained and they will be published soon in the book.

2. Salt Spoil Heap Karst

In the suburbs of Berezniki the participants had seen a peculiar karst in the spoil heaps of the rocks extracted onto the surface and stockpiled in the form of heaps. The heaps are as high as 50 to 80 m with the area of tens hectares and of tens and hundreds of millions m3 in volume.

The material of the spoil heaps consists of salt rock crumble, clay flakes and various inclusions contained in the salt mass. The grain sizes are 1 to 2 mm to 1 to 2 cm. During the material recrystallization process they increase. The form of the grains is irregular and the tinge is light-grey and motley.

Due to the natural compaction the spoil heaps material is cemented and turns from a loose and wet mass into a dense polymineral salt rock. The porosity of fresh material is 40-50%, but that of the old material at the heap foundation is 0-2%. Settlement of the stockpiled heaps due to the material compaction comes up to 15 to 20%. Constant addition of new material taking place along with the natural compaction, sharp differences in the material properties deposited in different parts of the stockpile profile bring about the development (contour extrusion swell) and the appearance of catastrophic (rockslide of 100 to 300 thousands m3 in volume) deformations.

Fig.2 The general view of the corrosion-and-gravitation cavity system
in the moment of collapse

Coarse granularity, jointing (compaction, relaxation, weathering) initial looseness of the stockpiled mass condition high water permeability of the heap to a considerable depth, unlike natural outcropping of salts being water permeable due to the structural properties, plasticity and absence of cracks. In connection with this on the heap surface there forms a peculiar karst relief (mesorelief) differing from the corrosion relief (microrelief) of the salt surfaces in the natural outcrops of salt rock.

Areal water permeability, high solubility of the material, presence of insoluble admixtures and dense non-uniformity of the spoil heaps predetermine the conditions of the atmospheric precipitation penetration and of the formation therein of a peculiar hydrodynamic zonality.

The following zones are brought out: the surface water mobility zone, the aeration zone and the horizontal circulation zone. The sources of the spoil heap water recharge are: moisture pressing at the gravitational dewatering of newly-piled heaps containing 8-9% of water, the atmospheric precipitation income (500-600 mm/yr) and the atmospheric moisture condensation. The water in the heaps is in the form of brines (100-350 g/l). The pressed brines are formed near the fill line and have local spread. The main amount of brines is formed at the expense of atmospheric moisture, precipitation in particular. The greater part of the vertical profile of heaps is occupied with the aeration zone. It is characterized by high water permeability, particularly in the upper karstified part. Two subzones are formed herein: the subzone of vertical movement of dissolved substances and insoluble inclusions as thick as 2-7 m, and the accumulation subzone of washing-in of insoluble material forming a thin clay-dressed continuous-discontinuous seam. The latter is a relative water-resist layer along which a part of atmospheric precipitation flows down to the slope foot. In the near-slope part of the spoil heaps the seam is included in accordance with the scarp. On the heap surface in the depth of 1-5 cm a denses salt as thick as 1 cm is formed due to moisture evaporation.

The horizontal water circulation zone (the "brine-saturated zone") is situated in the lower part of the heaps. The brines flow is directed towards the heap periphery, and the discharge is through springs on their foot at the expense of the filtration into the deposits at the heap foundation. The flow rate varies in a wide range of 0.1-5.0 l/s and more. The brine filtration rate into the underlying deposits is defined by the water permeability of the latter, the presence or absence of an artificial shield and the bed relief. In separate cases it can reach some millimeters a day. At approximate estimation, hundreds of thousands of tons of salts are carried out in a dissolved state. In places around the springs, peculiar salt deposits resembling sinter, snow and in cavities-sintered saline aggregates are formed. The leaching forms of secondary deposits are of great interest.

Within the limits of the spoil heaps, surface and underground karstic features are formed. The surface forms are mainly conditioned by the water movement along the surface in the aeration zone. They are represented by negative (swallow holes, wells, tubular formations, trenches, tunnel-shaped holes, rills) and positive (ridges, protrusions and outliers) varieties. Outlier forms are genetically linked with conveying lines remnants (pieces of metal, rubber and corrugated asbestos) which isolate spots on the spoil heap surface from precipitation and cause formation of remnants of various forms and sizes. Comparing the time which has passed since the function of the spreading conveyers has been stopped and the height of the outliers one can come to a conclusion about the rate of the karstic process on the spoil heap surface:for tens of years their area reduces by 0.2-0.5 m which corresponds to 20-50 mm/yr.

Underground stockpiling forms practically are not studied. Analysis on the rate on the dissolving process testifies the fact that inside the spoil heap there must be cavities of considerable size . At present the author has found small caves along the periphery of the stockpiles around karst springs. The caves are small channels formed by dissolving and erosive action of underground flows. One of the caves examined is about 30 m long (Fig.3). The path of an underground stream is traced on the surface with collapses and corrosion openings. The walls and roof of such caves are very unstable due to their rapid evolution being transformed at the expense of subsequent roof stripping into karstic-erosion trenches. In case of an underground stream forming a new watercourse they become water collectors and watercourses of periodic drainage. Intensive dissolving of the stockpiled material and carrying off the salts from the spoil heap is a serious ecological problem. Around the heaps there are salinization zones streching along the paths of ground water. It is believed that along with karstification the process of carrying salts out of the spoil heaps increases. In the areas adjacent to the heap foot ponds are formed with saline water in which precipitating of salts takes place. The saline ponds together with the feeding water also become contamination sources of ground water in the area around the spoil heaps. Protection measures against the karst of saline spoil heaps and salinizaton of surface and ground water must be comprehensire and multipurpose. The most effective and radical measure for this purpose is elimination of spoil heaps by stowing spoil salt rock in worked-out underground space.

SOUTH EXCURSION

The places of this excursion are situated in the environs of Kungur Town, 90 km to the South-East from Perm. This town is located near the boundary between the East Europian platform and the Pre-Ural foredeep. The 20-25 km wide stripe of sulfate rocks (gypsum and anhydrite) is reaching here from the South to the North. The sulfate rocks lay nearby from the surface and rivers open them on 30-80 m deep. Gypsum karst is developed here everywhere and we have many problems with building and use of waters.

There are more than 100 gypsum caves in this area. The most famous of them is the Kungur Ice Cave.

A large cave, an unique monument of nature and history of the Urals, Known from time immemorial, is situated near Kungur Town (Middle Preduralje), 100 km south-east from Perm, a regional center of the Urals. The first mention of the cave is associated with the name of Ermak- a legendary subjugator of Siberia. Folk traditions and chronicles told us much about Ermak and his squard's winter stay near the cave in the 70's of the 16th century when he boated up the Silva River. Ancient ditch and earth wall, separating "Ermak's site" near a cave entrance, a place at the mountain brink, where, according to chronicles, march participants lived in dug-outs, have retained up to now.

The cave is especially famed for its ice formations: great hoar-frost crystals, fantastic stalactites, stalagmites, cascades and columns decorating cave's arches. Early in the 18th century the cave assumed the name "Ledjanaja"(Ice), so a high bank of the Silva River, where an entrance to subsurface labyrinth was situated in, correspondingly, got the name "Ledjanaja Mountain". The mountain is formed by gypsum and anhydrite interbedded with thin layers of limestone and dolomite.

The structure of Kungur Cave contributes to natural air circulation. The cave consists of several horizontal galleries 10-40 m wide, 2-10 m high spreading from a bank solpe into Ledjanaja Mountain at depth of 0.6 to 0.8 km. Their remote parts, being a continuation of the cave, are pluged with lumpy and clay material. The outlets situated close to the river side are also blocked with slid lumpy and clayey soil. Nowadays only one outlet in the basement of 25 m high gypsum precipice is preserved. Galleries associated with the joints of north-east and north-west directions are at the same or 7 m higher of the Silva River leve l and form a single floor at the depth of 60 to 70 m below the plain surface of Ledjanaja Mountain. When intersecting each other, the galleries are united to form a system of labyrinth. The total length of known passages makes 5.6 km.

Fig.3 Source cave in the edge of spoil salt heap

1-clay-and-salt spoil heap;2-deforme d clay-and-salt spoil rock;3-stockpile bench;4-rockslide bench;5-underground stream and its hidden watercourse;6-examined part of the underground channel;7-watercourse of a temporary stream; 8-salted source with an absorbing sinkhole;9-salted lakelet;10-karsthole over the underground stream watercourse;
11-comlex sink-and-swallow hole with relaxation cracks on the edges;12-corrosion (infiltration) opening; 13-slump hole;14-blocks of collapsed rock

The Silva River is at a distance of 0.1 km from the cave entrance. The terrace above the flood plain is 0.1 km wide. The terrace disappears down stream, so the foot of Ledjanaja Mountain is washed by the river. When a flood sets in, river water enters subsurface channels causing a rise of water level in subsurface lakes. In a low water period water level of subsurface lakes is 0.1-0.4 m higher than the river. River water aggressive to gypsum played an important role in formation of Kungur Cave. As result of the thawing and rain water percolation, vertical clefts and organ tubes (cylindrical channels) crossing gypsum roof at various height (usually about 15-20 m) were formed in the ceiling of horizontal galleries. 85 of the 146 investigated tubes were filled with loose soil and had debris cones under a tube mouth and sinkholes on the mountain surface.

A cross-section of the cave represents an air conducting system that reminds us a huge oven with tubes 60-70 m long screened with oven-doors made of clayey soil. There is an ascending draught of air in winter. The doors are open, cold air rushes into the cave. As moving deeply into the cave, the air transmits its cold to the walls, gets warmer and lighter and through cracks and organ tubes moves upwards to carry away and disperse underground warm. In summer when temperature is raised up to +5° C, the reverse, descending draught of the air is observed. A cooled flow of air (0° C) escapes from the cave through the opened doors. Cool air is replaced by warm flows entering the cave through vertical channels. That is why it is always warm in the upper parts of vertical channels and, on the contrary, it is always cold in the near entrance grottoes, where winter and cold winds, preventing cave warming up in summer, reign. In the result of many years' accumulation of cold, an ever-frost zone has been formed in near entrance part of the cave. A frozen rock armour and ice filling joints prevent thawing water percolation. At present a zone of many years ice spreads from the entrance deeply into the cave at a distance of 0.17-0.2 km. The total square of many y ears ice makes 500 m2, the volume -350 m3. At a distance of 0.25-0.27 km from the entrance there is a zone of seasonally frozen ground rich in ice flowstone formations: stalactites, stalagmites, columns and cascades. Infiltration water enters there cooled up to 0° C to form fantastic ice flowstone but me lts in summer. Outside a winter 0° C -isoterm there is an extensive warm part of the cave. Moving away from the entrance, air and rock temperature of every other grotto gets warmer, achieves its maximum (5.3° C, Grjazny Grotto) and remains constant in parts of the cave not visited.

Early in the 20th century, before the construction of entrance doors, changes of temperature and subsurface ice were due to natural reasons. When vertical channels was filled with ice and fallen jumpy material grottoes became warmer, ice disappeared. A situation changed when in the result of rock collapse or washing away of tubes filling material a new vertical channel was opened. Air circulation was many times increased. Ice spread over the cave. The states of ice formations and temperature regime have been greatly changed after construction of entrance tunnels to cave for tourists. Nowadays the warming of cave and loss of its picturesque ice decoration in the result of mass tourist attendance bring a great trouble.

There are two possible ways to improve the situation: 1) to reduce the number of visitors; 2) to compensate high heat inflow by accumulation of cold in winter.

There is a karst station near the cave. The karstologists who work there make different observations in the cave and in the area more than 40 years. Some interesting obscure phenomena were discovered in the cave. In the cave galleries and grottoes we can observe hydratation of anhydrite, ancient and modern deformations of cave ceiling, formation of karst breccia, dynamics of ice forms, sediment of aerosols and etc.

The Southern Excursion also includes visit to the Ice Mountain, examination of the karstic relief above the cave and trip to Kishert village where participants had seen one famous sinkhole.