1.0.1 With view to ensuring the safety and applicability of building foundation excavation engineering in collapsible loess regions in each link and realizing technical advancement, economic rationality and environmental protection, the Specifications is formulated.
1.0.2 The Specifications is applicable to the technical safety and management for investigation, design, construction, detection and monitoring of building foundation excavation engineering in collapsible loess regions.
1.0.3 For building excavation engineering, foundation pit as well as the engineering geological and hydrogeological conditions within certain range around the foundation pit, excavation concentration, surrounding environment, foundation pit importance, possibility of soaked by water, construction conditions, service life of retaining and protecting structure and the like shall be taken into comprehensive consideration. Meanwhile, the elaborate design, rational layout, strict construction and effective supervision shall be realized by way of combination with engineering experience.
1.0.4 In addition to the requirements of the Specifications, building foundation excavation engineering in collapsible loess regions shall also comply with those stipulated in the current relevant standards of the nation.
2 Terms and Symbols
2.1 Terms
2.1.1 collapsible loess
the loess of which the soil structure is rapidly damaged and visibly collapsed after being soaked by water under pressure
2.1.2 building foundation pit
the space below the ground (including foundation trench) that is excavated for carrying out building (including structure and building) foundation and basement construction
2.1.3 foundation pit wall
certain side that is a part of foundation pit enclosure
2.1.4 surroundings foundation pit; surroundings around foundation pit
a general term of those including existing building (structure), road, underground facility, underground pipeline, rock-soil mass and underground water within the influence region of pit excavation
2.1.5 retaining and protecting for foundation excavation
the retaining, reinforcement and protective measures adopted for foundation pit wall and surroundings for the purpose of ensuring the safety of underground structure construction and surroundings around foundation pit
2.1.6 slope ratio method
the pit excavation construction method without the use of retaining and protection measures, which maintains the stability of foundation pit wall through the strength of soil mass after step-slope at reasonable slope grade
2.1.7 soil-nailed wall
the retaining and protecting structure composed of foundation pit wall reinforced with soil nail and protective covering, etc.
2.1.8 cement-soil wall
the gravity retaining and protecting structure in types of grilling or wall, which is mutually overlapped by soil-cement piles
2.1.9 soldier piles
the retaining and protecting structure for foundation excavation, which is composed of certain pile type in queue
2.1.10 ground anchor
the tension member composed of grouting in hole and the steel bar or steel strand that is arranged in drill hole and whose end is stretched into stabilized soil layer
2.1.11 top beam
the reinforced concrete connecting beam or steel connecting beam arranged at the top of retaining and protecting structure
2.1.12 waist beam
the reinforced concrete beam or steel beam that is arranged below the top of retaining and protecting structure and transfers bearing point force of retaining and protecting structure, anchor rod or inner support
2.1.13 bearing point
the horizontal constraint point of anchor rod or support system to retaining and protecting structure
2.1.14 stiffness of fulcrum bearing
the ratio between horizontal reactive force of anchor rod or support system to retaining and protecting structure and its corresponding displacement
2.1.15 embedded depth
the embedded depth of piling wall structure below the base of pit excavation
2.1.16 cut-off curtain
the continuous waterstops adopted for stopping or reducing the seepage of ground water around foundation pit or bottom ground water into foundation pit
2.1.17 area of protection
the area within the protection distance around the foundation pit
2.1.18 information feed back construction method
the construction method in which geological conclusions and design parameters are verified, construction safety is determined and construction scheme is timely corrected on the basis of the geological condition and monitoring data on the construction site
