建筑施工外文翻译---深基坑施工的安全监测和预警

附 录 1. 外文资料原件及译文 （ 1） 外文资料原件 Safety Monitoring and Early Warning for Deep Foundation Pit Construction Haibiao WANG【 1】 ， Haixu YANG 【 2】 , Xibin DONG 【 3】 , and Songyuan NI【 4】 1.School of Engineering Technique, Northeast Forestry University, Harbin,Heilongjiang 150040, China; PH (086) 451-82191771; email: 2.School of Civil Engineering , Northeast Forestry University, Harbin, Heilongjiang150040, China; PH (086) 451-82190402; email: 3.School of Engineering Technique, Northeast Forestry University, Harbin,Heilongjiang 150040, China; PH (086) 451-82190392; email: 4.School of Engineering Technique, Northeast Forestry University, Harbin,Heilongjiang 150040, China; PH (086) 451-82190335; email: ABSTRACT Based on an engineering project, this paper initially establishes an observation point for foundation pit and then determines monitor warning value. During project construction, we carried out an experiment on the horizontal movement and settlement and inclination of adjacent buildings and promptly monitored the foundation pit., Scientific analysis of the data is presented. This work is designed to provide for effective measures to implement security alerts for foundation construction.Detailed analysis examines the causes of deformation of foundation pit and offers a reasonable treatment measure. Results offer some scientific basis and technical measures to guarantee deep foundation project construction security and more knowledgeable engineering construction. With the rapid development of urbanization in China, the deep excavation works require have been put forward strict demand regulations concerning due to the requirements of the spatial location, structural stability and using function. Deep excavation engineering is mostly carried out in areas of heavy traffic and dense construction. The complexity associated with deep excavation depth and difficult construction creates environments where serious accidents can occur. The deep excavation work is a wide-ranging and integrated engineering process. Previous research on accidents in national deep foundation pit engineering found the general accident ratio was about 20% of that of the deep excavations work (Tang, 1997). Most accidents in urban areas were caused by foundation pit support. In deep excavation engineering, both the strength and deformation of the supporting structure and the surrounding environment affected by pit deformation should be considered (Sun, 2006).The pit support systems are always temporary facilities with fewer safety considerations and more hazards. Working status and conditions are more complicated and uncertain. Thus, during the construction process, dynamic monitoring and control is very important. The content of deep excavation-site monitoring generally includes the horizontal displacement of supporting structure, tilt displacement of neighboring buildings, sedimentation of adjacent roads and so on. A monitoring crew should provide timely feedback information (Liu, 2006) to detect any problems and provide early warnings for reducing disasters. A monitoring program that provides critical information and manages deep excavation construction scientifically and effectively is the key to successful deep excavation construction (Liu et al., 2007). 1 ENGINEERING BACKGROUND The deep foundation pit engineering was located at the city center. The ground form type of geological investigation works is the tectonic denudation and the slow hillock at slope base, which was equal to the forefront of third terrace of the Yangtze River and the southwest bordered on the first terrace of the Chengdu plain. Soil conditions. Through the field investigation by the Geological Survey Department, the soil conditions at the engineering site are shown as Table 1. Table 1. Physical-mechanics index of foundation soil. Soil density Plasticity Cohesion Internal No. Name of Soil Samples /kN.m-3 Index c/kpa friction Angle/0 1-1 Miscellaneous fill soil 19.1 13.1 5 20 1-2 Plain soil 19.3 11.8 15 12 2-1 Silt clay 19.5 12.3 25 14 3-1 Clay 18.5 13.1 42 16 Hydrological geology conditions of underground. Surface water of the proposed site is not present-development, and the underground water was dominated by the bedrock fracture water. and the small amount of the upper perched water filled in the 1-1 layer of soil-with-filled.They mainly were supplied by the precipitation and infiltration of surface runoff.The water level of the upper perched water is discontinuous and had smaller water volume. The bedrock fracture water grew well nearby the contact face between the bedrock and the overburden layer,and formed the passageway of underground water along the penetration crevasse partly.Thus, the underground water seeped out from the surface along the slope when the side slope was excavated. The results of the analysis of environmental conditions and water quality of groundwater samples indicated that the groundwater in the site did not corrode a concrete structure, but had weak corrosiveness to the steel structure. 2 DESIGN OF FOUNDATION PIT SUPPORT STRUCTURE The pit supporting scheme generally is classified to is of two kinds: one is the earth nail wall, and anther one the second is an anchor-retaining pile. The earth nail wall is made up of the reinforced soil, and the earth nail and the board which was placed in the soil. Given the strengthen of the earth nail in situ and the combination with the spraying-up surface, the natural soil body forms the earth bulkhead. This which is similar to a gravity retaining wall that resists the earth pressure coming from the wall and the other external forces and enhances the stability of the entire side slope (foundation pit). Anchor-retaining pile takes the drill hole filling pile as the retaining wall, and the pile and the anchor rod affects commonly to achieve the stability of slope. Mechanism of anchor-retaining pile is that the dense slope protection piles have high Bending Resistance and shear capability, simultaneously the anchor section of the anchor rod and the soil body take the pretension strength together to the dense slope protection piles, and prevent deformation of foundation pit supporting system. Combined effect of anchor rod and slope protection piles enhances the stability of entire supports and protection system. Anchor-retaining pile is suitable to all kinds of clay, sandy soil and the earth layer with higher groundwater level, especially the cohesive soil peripheral with big centralized loads or varying loads (Lu, 2003).For the deeper excavation of foundation pit, based on the principle of guaranteed safety, this project proposed to use anchor-retaining pile for supporting the foundation in the project. (1) In AD section of foundation pit, the following parameters were set up: 900mm of guard stake pile diameter, 1300mm of piles interval, 14 meters length of filling pile with man-power dig hole, 15inclination angle and 15m length for pile of non-prestressed anchor rod which was established 3m under the natural ground. (2) In AB axis section of foundation pit, the following parameters were set up: 900mm of guard stake pile diameter, 1300mm of piles interval, 13.4 meters length of filling pile with man-power dig hole, 15inclination angle and 15m length for pile of non-prestressed anchor rod which was established 3m under the natural ground. (3) In BC section of foundation pit, the following parameters were set up: 1000mm of guard stake pile diameter, 1300mm of piles interval, 7 meters length of filling pile with man-power dig hole, 15inclination angle and 15m length for pile of non-pre-stressed anchor rod. (4) In AB axis section of foundation pit, the following parameters were set up: 1000mm of guard stake pile diameter, 1300mm of piles interval, 7 meters length of filling pile with man-power dig hole, 15inclination angle and 16m length for pile of non prestressed anchor rod. 3 FOUNDATION PIT MONITORING This foundation pit engineering monitoring rests on the Engineering survey Standard (GB50026-93) and Construction Distortion Survey Regulations （ JGJ/T8-97） .The total length of the foundation pit is 176 meters, the biggest digging depth is 9.8 meters, and the smallest digging depth is 4.2 meters. According to the standard, the security rating of this foundation pit engineering is first-level. Before project construction of the foundation pit engineering, reference points B1 and B2 were established in advance. The coordinate system of the horizontal displacement monitoring was set up according to the reference points. The horizontal displacements observed were one time every 5 days during the progress of project construction. 3.1 Observation Point Arrangement Total 15 observation points were set up separately around the foundation pit for monitoring the horizontal displacement of the supporting and protecting structure top. This project installed the observation points underground during 5 days. The arrangement of observation points were shown in figure 1: 3.2 Foundation Pit Monitoring Facilities According to Engineering survey Standard， to satisfy the building safety fortification requirement, the horizontal displacement monitoring in the project construction of foundation pit engineering uses total station TOPCOM GTS-701. The settlement observation used level browser TOPCOM AT-G2. The elevation probable error in the settlement monitoring points should not be bigger than 0.2mm, and the elevation difference error in the adjacent deformation monitoring points should not be bigger than 0.13mm (Long et al., 2005). 3.3 Monitoring Security Value According to the project standard and the determination principle of security value, the security value of the foundation pit engineering was determined as follows: the horizontal displacement around the foundation pit did not surpass 40mm, and the displacement speed did not be bigger than 5mm/d; for the road settlement, the settlement value did not surpass 30mm and the settlement speed did not be bigger than 2mm/d; for the settlement and inclination rate of adjacent buildings, the biggest settlement differences of two nearby test points did not surpass 3. Fig.1 Arrangement of horizontal displacement observation points. 3.3 Monitoring Security Value According to the project standard and the determination principle of security value, the security value of the foundation pit engineering was determined as follows: the horizontal displacement around the foundation pit did not surpass 40mm, and the displacement speed did not be bigger than 5mm/d; for the road settlement, the settlement value did not surpass 30mm and the settlement speed did not be bigger than 2mm/d; for the settlement and inclination rate of adjacent buildings, the biggest settlement differences of two nearby test points did not surpass 3. 4 MONITORING RESULTS AND ANALYSIS OF THE FOUNDATION PIT After the excavation and the foundation construction, the monitoring results were recorded and arranged and analyzed for early warning timely for foundation pit. The time-history curves(fig.2fig.9) corresponds to the initial period at four stages which include that the first layer excavation (the excavation depth was about 4m) and the second layer excavation(the excavation depth was about 6m) and the third layer was full-depth excavation and demolishing supporting and protecting system. 4.1 Monitoring and Analysis of Horizontal Displacement In the horizontal displacement monitoring for the sealing beams of the supporting and protecting structure of foundation pit, the horizontal displacement monitoring results of supporting and protecting structure around the foundation pit are shown in Fig. 2 to Fig. 5. The horizontal displacement time-history curve showed that the horizontal displacement of the peripheral supporting and protecting system increases fast in short-term and then becomes gradually steady. The horizontal displacement time-history curve also indicated that the horizontal displacement of the AB section is bigger, with 40.8mm at spot S5, 33.0mm at spot S6, 27.5mm at spot S4, 25.6mm at spot S3, 32.6mm at spot S13 of the CD section. Among these, the displacement of spot S5 achieves the security value, and that of S6, S13 approach the security value. The test group gave the warning when submitting test results timely, made the risk prompt, and proposed the supporting and protecting structure processing scheme finally. Fig.2 Time-history chart of horizontal Fig.3 Time-history chart of horizontal displacement monitoring of the displacement monitoring of the supports and protections in AD section supports and protections in AB section Fig.4 Time-history chart of horizontal Fig.5. Time-history chart of horizontal displacement monitoring of the displacement monitoring of the supports and protections in BC section. supports and protections in CD section. 4.2 Inclination Monitoring and Analysis of Foundation Pit During each early stage from foundation excavation to demolishing supporting and protecting system, inclination rate increases fast at the short-term, then becomes steady gradually. The inclination observed value of the Q2, Q3 and Q4 is 1.18 , 1.05 , 0.86 respectively, and other observed value are smaller; and the observed value develops quickly when demolishing the supports, as shown in fig.6 and fig.7. For guaranteeing the scene construction safety, the measurement results were submitted to Construction Organization. Fig.6. The time-history chart of Fig.7. The time-history chart inclination of adjacent building of inclination of adjacent building monitoring in AB section. monitoring in BC、 CD section. 4.3 Monitoring and analysis about settlement of the foundation pit During each early stage from foundation excavation to demolishing supporting and protecting system, the settlement increases fast at the short-term, and then becomes steady gradually, and the settlement increases fast after demolishing the supports. Settlement observed value of the C2, C3 and C4 is 16.5m, 15.5m, 13.2m respective, other observed value is small, as shown in fig.8 and fig.9. For safety, the measurement results were submitted to Construction Organization. Fig.8. The time-history chart of settlement Fig.9. The time-history chart of settlement of roads monitoring in AB、 AD section. of roads monitoring in BC、 CD section. 4.4 Forewarning Management and Safety Control In the course of safety monitoring of the foundation pit, it is an important work before safety supervision to determine monitor warning value reasonably according to pit bracing calculation. It can bring disadvantageous influence to the foundation pit management if the monitor warning value is over sized or too small. When the monitor value achieves or approaches the security value, it will implement the safe early warning plan promptly. The monitoring personnel should send the forewarning document to development organization and the overseeing unit promptly, and inform the Construction Unit and the Designing Department. The Construction Unit calls the related personnel to carry on the scene investigation, coordinate organization promptly, formulate scientific effective technical measures and control the security of the foundation pit. On the one hand it should monitor its forewarning spot strictly, on the other hand it also requests the construction unit to carry on the foundation pit work according to the provisions in the construction process and execute reinforcement processing deferring to the technical program . In the course of safety monitoring of the foundation pit, settlement of roads and inclination of adjacent building monitoring value was smaller than the warning value. In the horizontal displacement observation of the foundation pit, displacement increased fast when excavating (depth was 4.2m) the first layer, and the development speed was rapid. For the increasing tendency is obvious, the observation frequency was increased for partial observation points, so as to the inclination observation. Therefore, the risk warning of the foundation pit was given. In the proposed plan, strengthen measure was adopted to the supporting and protecting system, not only the knee bracing but also two braces in the broadside were increased. All these had the very good effects for the stability to the foundation pit. Then second excavating and comprehensive excavating were carried on, after strengthening the supports, the movement is stable. But after demolishing the supports, the horizontal displacement of the foundation pit increases rapidly once more, which shows the validity of strengthened supports , and confirms the necessity and the scientific nature of safety monitoring of the foundation pit. 5 CONCLUSIONS Through the horizontal displacement and settlement and inclination of adjacent building monitoring for foundation pit promptly, safety control can be carried on scientifically and effectively for the project construction of the foundation pit becomes true (Zhu et al., 2006). According to progress of the project construction and analysis of the monitor data, it can timely and effectively obtain the safety forewarning, and realize the information construction with scientific idea. And adopting effective technique means to treat supporting and protecting structure of the foundation pit according to the monitor data, it could avoid the personal injuries and th