箱涵基坑支护技术交底.doc

交底内容：
1. 对实际开挖深度≤5.0m地段的基坑，上面1.2m采用1：1放坡，坡面喷射C15混凝土硬化层，下面采用拉森钢板桩支护；若遇到相对较差土层，采用密排拉森钢板桩支护。钢板桩顶设一道支撑，支撑选用32号双翼工字钢。
2. 对实际开挖深度＞5.0m地段的基坑，采用密排钢板桩支护，桩顶以下0.5m设一道支撑，支撑选用32号双翼工字钢，水平间距不大于4.0m。
3. 施工过程中要加强对基坑的监测，每隔20.0m设一个沉降和位移观测点，发现有异常情况时及时采取应急处理措施，如采取回填反压土或坑顶卸土的方法。
4. 基坑降水采用井点降水，保证水位在坑底以下0.5m；施工过程要做好排水工作，坑底、坑顶均应设排水沟（400×350）和集水井（1000×1000×800）。
5. 基坑土方开挖采取分段、分层开挖，每层开挖深度不大于1.5m，每段开挖长度小于40.0m。坑底以上30.0cm土采用人工开挖，以免扰动原状土。
基坑施工过程中，在2.0m范围内严禁大型载重车辆行走，保证基坑安全；同时基坑周边应设钢围栏。
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.