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一、溶洞分布情况某桥4号墩基采用圆形鋼板桩围堰明挖基础。施工时水深1米多,河床复盖层上部沙夹卵石平均厚3.2米,下部为石灰岩层。經围堰抽水清除复盖层后,发现基岩溶洞数处大量涌水,虽以10台抽水机(总排水量为1896吨/小时)仍保持基坑水深0.8米以上,无法进行清除。当时鋼板桩围堰系按第三孔38米上承鋼板梁設計,如将第三孔梁跨改为36米上承板梁,則可基本避开溶洞涌水部。决定改变孔跨后,墩基移动2米。在1960年10月进行水下清除,将溶沟范围部分(下游涌水区)沙夹卵石复盖层清理,随后在涌水区灌注水下混凝土(图1),
First, the distribution of karst cave No. 4 pier foundation using circular steel sheet cofferdam foundation digging. Construction depth of more than 1 meter, the upper bed cover sandblasting the average thickness of 3.2 meters, the lower part of the limestone layer. After the cofferdam was drained to remove the overburden, a large amount of gushing water was found at the number of bedrock cavities. Although the water depth of the foundation pit was maintained at 0.8 m or more with 10 water pumps (total displacement of 1896 t / h), the water could not be removed. At that time steel sheet cofferdam according to the third hole 38 meters on steel plate girder design, such as the third hole beam to 36 meters on the board beam, you can basically avoid the cave water department. After deciding to change the hole span, the base of the pier moves 2 meters. Underwater removal was carried out in October 1960, and the sand-gravel coating was removed from the gully area (downstream gushing area), followed by infiltration of underwater concrete into the gushing area (Figure 1)