Shipworms Are Master Diggers and the Original Shield Tunnelers

The shipworm has a long thin body about 10cm long. It is a relative of the clam (there are very small shells at the tip of its wormlike body). It feeds on driftwood and wooden ships, boring tunnels deeper and deeper into the wood as it eats. The shipworm’s tunneling technique is an amazing work of craftsmanship. The hard shells at the tips of its body function both to shave away the wood and to support the walls of the burrowed hole from the inside to prevent it from collapsing. Furthermore, as it bores the hole with its shells, it secretes a chalky substance from its mouth. This secretion lines and hardens the inner walls of the hole as the shipworm advances deeper.

Transfer/Dispose/Circulate:: Excavation

Other

In the 18th century, the French engineer Marc Brunel imitated the tunneling technique of the shipworm and successfully constructed an underwater tunnel beneath the River Thames. This tunneling technique was called “shield tunnneling,” and is still in wide use today.

Tunneling shield.

By using a method that hardens the internal walls as the tunnel is bored, tunnels can be created under riverbeds or seabeds, and through areas where the earth is unstable.

Query	Affected	Num. rows	Took (ms)	Actions
SHOW FULL COLUMNS FROM `contents`	16	16	1	maybe slow
SELECT CHARACTER_SET_NAME FROM INFORMATION_SCHEMA.COLLATIONS WHERE COLLATION_NAME= 'utf8_general_ci';	1	1	1
SHOW FULL COLUMNS FROM `users`	10	10	1	maybe slow
SHOW FULL COLUMNS FROM `groups`	4	4	1	maybe slow
SHOW FULL COLUMNS FROM `permissions`	5	5	1	maybe slow
SHOW FULL COLUMNS FROM `groups_permissions`	3	3	1	maybe slow
SHOW FULL COLUMNS FROM `groups_users`	3	3	1	maybe slow
SHOW FULL COLUMNS FROM `contents_searches`	6	6	1	maybe slow
SHOW FULL COLUMNS FROM `attachments`	11	11	1	maybe slow
SHOW FULL COLUMNS FROM `attachments_revs`	13	13	1	maybe slow
SHOW FULL COLUMNS FROM `contents_related_items`	5	5	1	maybe slow
SHOW FULL COLUMNS FROM `related_items`	6	6	1	maybe slow
SHOW FULL COLUMNS FROM `contents_related_items_revs`	8	8	1	maybe slow
SHOW FULL COLUMNS FROM `contents_tags`	5	5	1	maybe slow
SHOW FULL COLUMNS FROM `tags`	7	7	1	maybe slow
SHOW FULL COLUMNS FROM `tag_groups`	6	6	1	maybe slow
SHOW FULL COLUMNS FROM `contents_tags_revs`	7	7	1	maybe slow
SHOW FULL COLUMNS FROM `contents_revs`	18	18	1	maybe slow
SELECT `Content`.`id`, `Content`.`user_id`, `Content`.`last_edit_user_id`, `Content`.`post_date`, `Content`.`post_date_year`, `Content`.`post_date_month`, `Content`.`post_date_day`, `Content`.`title`, `Content`.`title_en`, `Content`.`content`, `Content`.`plain_content`, `Content`.`page_view`, `Content`.`flag`, `Content`.`mod_count`, `Content`.`created`, `Content`.`modified` FROM `contents` AS `Content` WHERE `id` = 194 LIMIT 1	1	1	0
SELECT `Attachment`.`file_name`, `Attachment`.`dir`, `Attachment`.`model`, `Attachment`.`foreign_key` FROM `attachments` AS `Attachment` WHERE `file_name` <> 'default.jpg' AND `Attachment`.`foreign_key` = (194)	1	1	0
SELECT `ContentsRelatedItem`.`content`, `ContentsRelatedItem`.`related_item_id`, `ContentsRelatedItem`.`content_id` FROM `contents_related_items` AS `ContentsRelatedItem` WHERE `ContentsRelatedItem`.`content_id` = (194)	11	11	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 1	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 2	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 4	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 6	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 7	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 8	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 9	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 9	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 9	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 11	1	1	0
SELECT `RelatedItem`.`code`, `RelatedItem`.`name` FROM `related_items` AS `RelatedItem` WHERE `RelatedItem`.`id` = 12	1	1	0
SELECT `ContentsTag`.`id`, `ContentsTag`.`tag_group_id`, `ContentsTag`.`mod_count`, `ContentsTag`.`tag_id`, `ContentsTag`.`content_id` FROM `contents_tags` AS `ContentsTag` WHERE `ContentsTag`.`content_id` = (194)	2	2	0
SELECT `Tag`.`name`, `Tag`.`comment`, `Tag`.`tag_group_id` FROM `tags` AS `Tag` WHERE `Tag`.`id` = 27	1	1	0
SELECT `TagGroup`.`code`, `TagGroup`.`name` FROM `tag_groups` AS `TagGroup` WHERE `TagGroup`.`id` = 3	1	1	0
SELECT `Tag`.`name`, `Tag`.`comment`, `Tag`.`tag_group_id` FROM `tags` AS `Tag` WHERE `Tag`.`id` = 175	1	1	0
SELECT `TagGroup`.`code`, `TagGroup`.`name` FROM `tag_groups` AS `TagGroup` WHERE `TagGroup`.`id` = 7	1	1	0
SELECT `RelatedItem`.`id`, `RelatedItem`.`code`, `RelatedItem`.`name`, `RelatedItem`.`created`, `RelatedItem`.`modified`, `RelatedItem`.`flag` FROM `related_items` AS `RelatedItem` WHERE `code` = 'function' LIMIT 1	1	1	0
SELECT `Content`.`id`, `Content`.`title`, `Content`.`title_en` FROM `contents` AS `Content` WHERE id = (NULL) ORDER BY `id` desc	0	0	0

Message	Memory use
Component intitailization	6.79 MB
Controller action start	6.83 MB
Controller render start	6.90 MB
View render complete	7.92 MB

Message	Time in ms	Graph
Core Processing (Derived)	338.02
Component initialization and startup	7.86
Controller action	47.09
Render Controller Action	107.40
» Rendering View	51.55
» » Rendering APP/views/contents/view.ctp	31.45
» » Rendering APP/views/layouts/default.ctp	18.15
» » » Rendering APP/views/elements/header.ctp	1.52
» » » Rendering APP/views/elements/content_sidebar.ctp	0.32
» » » Rendering APP/views/elements/footer.ctp	0.40

Shipworms Are Master Diggers and the Original Shield Tunnelers

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Shipworms Are Master Diggers and the Original Shield Tunnelers

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