حدود مجاز جابجايي ديوار گودهاي تسليح شده به روش ميخكوبي بر اساس سطوح خرابي سازه هاي مجاور گود

Allowable limit of soil nail wall deflection based on damage level of adjacent structures

احتمال خرابي و آسيب به سازه هاي مجاور محدوده گودبرداري همواره بعنوان يك مسئله چالش برانگيز در طول پايدارسازي ديوار گودبرداري هاي عميق با روش ميخكوبي مطرح بوده است. منشأ اين خرابي ها عمدتاً جابجايي هاي ايجاد شده در ديوارهاي گود با پيشرفت گودبرداري است. با اين وجود تا كنون ارتباط منطقي بين ميزان جابجايي هاي پيش گفته و ميزان خرابي قابل انتظار در سازه هاي مجاور ارائه نشده است. در اين پژوهش سعي گرديده است با تكيه بر10مطالعه موردي و90 تحليل عددي سه بعدي كاليبره شده و بهره گيري از آناليزهاي احتمالاتي، به ارائه حدود مجاز جابجايي ديوار ميخكوبي شده با توجه به احتمال آسيب به سازه هاي مصالح بنايي واقع در مجاورت گود پرداخته گردد. نتايج اين پژوهش ارائه دهنده سطوح خرابي سازه هاي مجاور گود تحت مقادير مختلف جابجايي مي باشد. سطوح خرابي پيشنهادي دراين مقاله، نشان دهنده ميزان خرابي محتمل درسازه هاي مجاور ديوارهاي ميخكوبي شده، باتوجه به فاصله سازه از ديوار گود و حداكثر مقادير جابجايي افقي ديواره گود و با در نظر گرفتن اثرات عمق گود و نوع خاك مي باشد.

Damage probability of structures caused by excavation wall movement is an important design aspect of support system in urban areas. This will be more important, if the adjacent structure be old or have low strength parameters. Frame distortion and crack generation are signs of building damage to excavationinduced ground movements which is a challenge in projects involving deep excavations. These highlight the importance of evaluation of building response in excavation projects. The aim of estimation and evaluation of building response is to establish limiting criterion for excavation support system design to certify the structure safety against undesirable damage. Thus, limiting criterion prepares a framework to determine the damage level of building based on excavation induced ground movements. Mentioned limiting criterion also is named Damage criterion or Damage model. Damage models are too practical before design progress of nailing wall. Based on uncertainty in data from excavation project and variability of the many factors that contribute to the response of nearby structures, existing Damage models are rare and generally need special instrumentation of excavation wall and nearby structures, so they cannot prepare a simple framework to use in practical situation.This paper describes a study of building response to excavationrelated ground movements and provides procedure for damage assessment of building near excavation projects. This study uses field data based on 10 case studies and 90 calibrated 3D FEM models in addition to probabilistic analysis to establish new simple damage criterion for design consideration of excavation supported by soil nail wall technique. Presented Damage model simply relates the damage level of structure to maximum displacement of excavation wall.To create this paper following stages are used:1.Case studies:31 deep excavation (16.731 meters) from expert companies are studied in first stage.2.First filtering of the collected data: part of collected data (14 projects of 27 projects) is eliminated from data base because of inaccuracy in the results of monitoring, unfavorable results in displacement caused by nearby galleries or underground facilities, inappropriate execution and etc. 3.Evaluation of the structures in the excavationaffected zone (EAZ). 4.Second filtering of database: part of firstfiltered data is eliminated from data base because of nondeductible conditions of structure in EAZ, mismatch between damage level and results of monitoring and etc. At the end of this stage only ten masonry structures (TMS) were selected to continue case studies. 5.Creating and calibrating FE models: at this stage, FE models are included excavation wall and adjacent structure were extended for each of TMS and were calibrated based on field results. 6.Idealization of calibrated TMS’s FE model (ICTM): each of calibrated TMS’s FE models were modified and idealized by removing water table, modification of excavation condition, simplification of structure frames and etc.7.Development of damage levels: in the last stage, DPI calculated from ICTM for each frame of structure and then compared with the value of excavation wall deflections. Finally, damage levels developed based on resulted database.