تعيين تنش افقي زمين با استفاده از آزمايش نفوذ مخروط: رويكرد پايگاه داده ها

Horizontal Stress Estimation Using CPT: A Database Approach

پايگاه داده ‌يي از نتايج محفظه‌ي كاليبراسيون آزمايش مقاومت نوك مخروط جمع آوري شده است. از اين پايگاه داده‌ استفاده‌‌ شده و اثر پارامترها و شرايط خاك (شامل: چگالي نسبي، تنش قايم، تنش افقي، مدول محدودشده، و نسبت بيش-تحكيمي) در مقاومت نوك مخروط مورد بررسي قرار گرفته است. با استفاده از اين بررسي ها، دانسيته‌ي نسبي و تنش افقي به عنوان پارامترهاي اصلي انتخاب و رابطه ‌يي بين آنها و مقاومت نوك مخروط پيشنهاد شده است. اين رابطه با محاسبه‌ي معكوس مي تواند جهت تعيين تنش افقي خاك بر اساس مقاومت نوك مخروط مورد استفاده قرار گيرد. ميزان دقت معادله با استفاده از پايگاه داده‌ي آزمايش هاي كاليبراسيون مخروط صحت سنجي مي‌شود. همچنين كارايي آن با دو معادله ي موجود پيشنهادشده‌ي ديگر پژوهشگران مورد مقايسه قرار مي گيرد. همچنين علت كارابودن و دلايل انتخاب پارامترهاي مورد استفاده بررسي و تحليل مي‌شود.

In order to perform a stress-deformation analysis of a geotechnical system, it is essential to know the in-situ stress state of the ground. The in-situ vertical stress can be simply determined if the depth and the soil density are known. However, it is more difficult to determine the in-situ horizontal stress. This is because it depends on several other soil characteristics, such as stress history and over consolidation history. Throughout the years, several additional sensors have been developed in order to supplement the data collected with the CPT test. Among the wide variety of sensors developed, the lateral stress module represents a promising tool for estimation of in situ lateral stress conditions from the interpretation of lateral stress penetration data. However, the popularity of the so called lateral stress cone has declined over the years due to constraints in both the instrumentation and the interpretation of measured data. In the present paper, a database of calibration chamber tests results is provided. Using the database, the effects of different soil parameters (such as relative density, in-situ vertical stress, in-situ horizontal stress, constraint modulus, and over consolidation ratio) on cone tip resistance have been studied. Among these parameters, relative density and in-situ horizontal stress are found to be the main effective parameters and a correlation between these parameters and cone tip resistance has been suggested. With a given relative density, the relationship can be used to estimate the in-situ horizontal stress of the soil upon measured cone tip resistance. The relationship has been validated with calibration chamber test database. Besides, its effectiveness has been compared with two other empirical correlations suggested by other researchers. The results indicate that the correlation proposed in this study can predict cone tip resistance better than the other two available correlations.