箱涵基坑支護技術交底.doc
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交底內容：
1. 對實際開挖深度≤5.0m地段的基坑，上面1.2m采用1：1放坡，坡面噴射C15混凝土硬化層，下面采用拉森鋼板樁支護；若遇到相對較差土層，采用密排拉森鋼板樁支護。鋼板樁頂設一道支撐，支撐選用32號雙翼工字鋼。
2. 對實際開挖深度＞5.0m地段的基坑，采用密排鋼板樁支護，樁頂以下0.5m設一道支撐，支撐選用32號雙翼工字鋼，水平間距不大于4.0m。
3. 施工過程中要加強對基坑的監測，每隔20.0m設一個沉降和位移觀測點，發現有異常情況時及時采取應急處理措施，如采取回填反壓土或坑頂卸土的方法。
4. 基坑降水采用井點降水，保證水位在坑底以下0.5m；施工過程要做好排水工作，坑底、坑頂均應設排水溝（400×350）和集水井（1000×1000×800）。
5. 基坑土方開挖采取分段、分層開挖，每層開挖深度不大于1.5m，每段開挖長度小于40.0m。坑底以上30.0cm土采用人工開挖，以免擾動原狀土。
基坑施工過程中，在2.0m范圍內嚴禁大型載重車輛行走，保證基坑安全；同時基坑周邊應設鋼圍欄。
Cards on the table contents:
1. On the actual excavation site of the excavation depth ≤ 5.0m, 1.2m above the 1:1 cut slope, slope jet C15 concrete hardening, the following support by Larsen sheet pile; If they are in relatively poor soil using closely spaced steel sheet pile retaining Larsen. Set up a steel sheet pile head support wings 32, I-beam support used.
2. On the actual excavation depth> 5.0m lot of excavation, using closely spaced steel sheet piles, pile top the following set up a 0.5m support wings 32, I-beam support used, the horizontal spacing of not more than 4.0m.
3. The construction process should strengthen the foundation of the monitoring, at intervals of 20.0m set up a settlement and displacement of observation point, when an abnormality is detected in time to take contingency measures, such as to backfill compacted soil or pit the top anti-dumping earth approach.
4. Foundation pit dewatering used to ensure the water level at the Bottom of the following 0.5m; the construction process to make the drainage work, pit bottom, pit roof drains should be located (400 × 350) and the set of wells (1000 × 1000 × 800).
5. Earthwork excavation pit to section, layered excavation, excavation depth of each layer is not greater than 1.5m, the length of each piece of excavation is less than 40.0m. Bottom 30.0cm above artificial excavation of soil, undisturbed soil to prevent disturbance.
Foundation construction process, is strictly prohibited in the 2.0m range of large-scale load vehicles to ensure the Pit; the same time should be set steel fence around the pit.