Fall cone test calibration for slope stability analysis.

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Bibliographic Details
Title: Fall cone test calibration for slope stability analysis.
Alternate Title: Kalibracija ispitivanja pomoću padajućega šiljka za analizu stabilnosti kosina.
Authors: Youssouf, Chalabi1 youcef.chalabi@univ-temouchent.edu.dz, Soufyane, Aissaoui2, Abdeldjalil, Zadjaoui3, Sidi Mohammed, Aissa Mamoune1
Source: Rudarsko-Geološko-Naftni Zbornik. 2026, Vol. 41 Issue 3, p197-205. 9p.
Subject Terms: *Slope stability, *Shear strength, *Shear testing of soils, *Geotechnical engineering, *Soil texture, *Calibration, *Soil consolidation
Abstract (English): Undrained shear strength is considered as an essential factor to assess the stability of natural slopes and embankments. Traditionally, this parameter is determined through laboratory tests, which are often costly and time-consuming. Recently, geotechnical research has shifted toward using the Fall Cone Test (FCT) for short-term strength estimation. However, prior studies focusing on pure clay soils have often overlooked the combined impact of soil texture and stress conditions on the reliability of FCT-derived values. To address this gap, undrained shear tests were conducted using both the FCT and pocket vane shear devices on samples exhibiting various degrees of consolidation and different textures. The findings demonstrate that applying a constant cone factor of 0.8 in the FCT yields inconsistent results compared to vane shear tests, as this factor fails to reflect the soil's consolidation state and the texture effect. To overcome this limitation, a new empirical expression for the cone factor, based on the overconsolidation ratio and fines content, is suggested. The results indicate that this approach significantly improves the accuracy of undrained resistance calculations by the FCT, thus providing a refined methodology for better risk management related to slope and embankments instability. [ABSTRACT FROM AUTHOR]
Abstract (Bosnian): Nedrenirana posmična čvrstoća jedan je od ključnih parametara za procjenu stabilnosti prirodnih kosina i nasipa. Uobičajeno se ovaj parametar određuje laboratorijskim ispitivanjima koja su često skupa i vremenski zahtjevna. U novije vrijeme geotehnička istraživanja sve se više usmjeravaju na primjenu ispitivanja pomoću padajućega šiljka (Fall Cone Test - FCT) za procjenu kratkotrajne nedrenirane posmične čvrstoće tla. Međutim, dosadašnja istraživanja, uglavnom provedena na čistim glinovitim tlima, često zanemaruju zajednički utjecaj teksture tla, stanja naprezanja i stanja konsolidacije na pouzdanost vrijednosti nedrenirane posmične čvrstoće dobivenih FCT-om. Kako bi se premostio navedeni nedostatak, provedena su ispitivanja nedrenirane posmične čvrstoće primjenom padajućega šiljka i ispitivanja posmične čvrstoće terenskom krilnom sondom, koja se u normativnoj praksi koristi kao referentna metoda. Ispitivanja su provedena na uzorcima tla različitoga stupnja konsolidacije i različitoga granulometrijskog sastava. Rezultati pokazuju da primjena konstantnoga koeficijenta korelacije vrijednosti 0,8 kod ispitivanja pomoću padajućega šiljka dovodi do nepodudarnih rezultata u odnosu na ispitivanje terenskom krilnom sondom jer takav koeficijent ne odražava stanje konsolidacije tla niti utjecaj granulometrijskoga sastava. Radi prevladavanja navedenoga ograničenja predložen je novi empirijski izraz za koeficijent korelacije koji se temelji na omjeru prekonsolidacije (OCR) i udjelu sitnih čestica u tlu. Dobiveni rezultati pokazuju da takav pristup znatno poboljšava točnost određivanja nedrenirane posmične čvrstoće primjenom ispitivanja pomoću padajućega šiljka, čime se osigurava pouzdanija metodologija za analizu stabilnosti kosina i nasipa te učinkovitije upravljanje geotehničkim rizicima u kratkotrajnim (nedreniranim) uvjetima. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
Description
Abstract:Undrained shear strength is considered as an essential factor to assess the stability of natural slopes and embankments. Traditionally, this parameter is determined through laboratory tests, which are often costly and time-consuming. Recently, geotechnical research has shifted toward using the Fall Cone Test (FCT) for short-term strength estimation. However, prior studies focusing on pure clay soils have often overlooked the combined impact of soil texture and stress conditions on the reliability of FCT-derived values. To address this gap, undrained shear tests were conducted using both the FCT and pocket vane shear devices on samples exhibiting various degrees of consolidation and different textures. The findings demonstrate that applying a constant cone factor of 0.8 in the FCT yields inconsistent results compared to vane shear tests, as this factor fails to reflect the soil's consolidation state and the texture effect. To overcome this limitation, a new empirical expression for the cone factor, based on the overconsolidation ratio and fines content, is suggested. The results indicate that this approach significantly improves the accuracy of undrained resistance calculations by the FCT, thus providing a refined methodology for better risk management related to slope and embankments instability. [ABSTRACT FROM AUTHOR]
ISSN:03534529
DOI:10.17794/rgn.2026.3.13