dong Dadong - 大洞

Détail


Nom de la grotte : Dadong - 大洞
Autres noms : Big Cave
Province, Préfecture, District :
Hunan 湖南省, Zhangjiajie Shi 张家界市, Dayong
Latitude Nord - Longitude Est :
29.178590 - 110.526280
Altitude (m) : 249
Développement (m) : 3 318
Profondeur (m) : 70
Profondeur - / + (m) : 0 /
Volume (m3) :
1Entrée : Dadong 大洞,

Carte



Description 1



2.5km south of Bai Jia Yu Cun. From main road which runs past Bai Jia Yu Cun take side road past quarry. Cross the river then turn left and follow path along the left hand side of the river.

10m wide dry stream bed with large water worn boulders runs into a 60m high entrance in the end of a steep sided blind valley. Immediately inside the entrance Sacre bleu! chamber has a choice of three main ways on: downstream, upstream, and up a very large set of gours to an major inlet. Less promising question marks include a bolt climb up on the RHS to possible high level passage.

The inlet passage is up a natural staircase in flowstone to an 8m climb (handline recommended). After 60m, the roof comes down and the 40m wide passage of boulders, gours, and a nitrate pit ends in a choice of two ways. To the right a 3m wide very warm passage with a flat mud floor which ends after 40m. To the left 8m wide passage with a crawling/stooping height shelf on the right and a series of deep puddles on the left goes for 70m before descending into a deep static pool which ended in a sump. Presumably late in the dry season the sump may dry out enough to be passable - siphoning might also be possible.

The upstream passage, Zut alors!, has been explored for 300m in pleasant 15m wide, 30m high walking passage with wades across the stream as it meanders from wall to wall. At the limit of exploration, the passage doglegs and the stream comes from a deep canal to the right, while straight on is a fossil passage ending in a choke, which has been penetrated as far as a stream flowing through the boulders on the right wall.

The downstream passage is impressive stuff, 50m wide and at least as high, with daylight coming in both ahead and from the entrance behind. After 200m, the daylight ahead proves to be from a second huge entrance, which adds an even larger stream to that already followed. The passage to the second entrance, Champs Elysees, is even more impressive than that already traversed, being a 400m long dead straight of big trunk passage. Downstream from the junction of the two streams is a further 200m of straight passage to a right-hand corner with a large nose of rock in the middle. From this corner it is possible to see straight out of the second entrance 600m away.

Continuing downstream is walking with occasional stream crossings, the passage retaining its generous dimensions. After 350m, there is a large pool which cannot be avoided, but fortunately it is only waist deep. The passage continues in the same vein beyond for 200m, where an area of large boulders is met, and the gradient of the stream increases. The boulders are easily climbed over, but when the floor is regained, the stream is missing - it flows away along The River Inseine, a 2m wide passage in the left-hand wall, which will need a traverse line fixing for safe exploration, although it has been traversed along for a few metres to where it turns right just before a small but furious cascade.

The continuing dry passage, the Shoe Shop, is as wide as that preceeding it, but even higher with the ceiling perhaps 80m away. The floor consists of sandy gravel with thousands of shoes partially buried in it. After 100m there is a climb over a few extremely large boulders. Here the ceiling comes back down, but is still some 30m high, and the passage turns left into a chamber, Cobblers. On the right at the corner is a fine series of active flowstone dams; the small stream flowing over them comes from a narrow passage with no draught and a diminishing airspace above deep water.

At the end of Cobblers, beyond a large, scummy lake (which can be passed on the left), the huge trunk passage seems to end. The obvious way on is straight ahead, where the stream from the flowstone dams trickles away into Dagobah, a 20m high, 4m wide rift passage. Dagobah is clean-washed and has flood-debris hanging everywhere - even from the ceiling. The passage draughts inwards and has been explored for some 100m down climbs (a 15m rope is needed as a handline) and across traverses round pools of most unsavoury-looking water. After the third pool traversed follows a fourth, which will probably require swimming.

Back in Cobblers, an ascent of the large boulder slope on the left (north) side leads to an aven and a hole down of about 10m, which has not been descended, and may require a rope. On the south side of Cobblers is a boulder and flowstone slope up into a 20m wide fossil passage containing dry gour pools. After 100m, the passage reaches an enormous boulder choke, 3720:1. On the right at floor level is an obvious way into the choke, which has been pushed for several tens of metres to a small oxbow which re-enters the choke. Climbing up the mud and flowstone which covers the face of the choke, there is a route round the left-hand side of the choke to reach a 15m wide descending passageway. Here there is another obvious route into the choke, which has been followed for several tens of metres without conclusion and which has a warm, strongly gusting draught outwards.

The descending passage leads over large boulders into a 1-2 metre wide rift, beyond which is an echoing black space. This is the Detention Level, an 80 by 40 metre chamber containing a jumble of large boulders with holes several metres deep between them, and lots of flood debris, mostly wood. At the eastern end is a ~20m pitch down to the Trash Compactor, a 5m wide canal full with lots of rubbish floating on the surface and a strong inward draught. At the western end, the chamber pinches in to become a narrow rift. This can be followed for some distance on an obvious traverse level from the top of the boulders, but this eventually peters out - the passage must be followed on the floor, until a narrow section with deep, murky water is encountered, where it is possible to back-and-foot traverse. The passage then enlarges again, ascending a boulder slope to reach a boulder-strewn ledge overlooking Cobblers, slightly to the south of the start of Dagobah, from which it is possible to climb down on the left.

Warning : The streamway responds very rapidly to rain and to snowmelt, and shows signs of dramatic flooding. In anything other than low water conditions the stream crossings can become extremely dangerous. If the first stream crossing is at all difficult do not go downstream, as the volume of water is more than double further downstream.

EML 2003.12.07

http://www.hongmeigui.net/
http://www.hongmeigui.net/
Analyse : Web
Site sur les campagne d’expéditions du club de Hong Mei Gui. Dans les provinces du Guizhou, Guangxi, Yunnan. Explorations dans les comtés de Leye, Nandan, Guilin. Données chiffrées sur les cavités topo données topo et photo chronique d’expédition.

6478 caractères - Lu 124 Fois

Bibliographie 1



http://www.hongmeigui.net/
http://www.hongmeigui.net/
Site sur les campagne d’expéditions du club de Hong Mei Gui. Dans les provinces du Guizhou, Guangxi, Yunnan. Explorations dans les comtés de Leye, Nandan, Guilin. Données chiffrées sur les cavités topo données topo et photo chronique d’expédition.
Source : Web


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