Modified Standard Penetration Test for Drilled Shaft Design in Weak Fine-Grained Rocks

2021 ◽  
pp. 036119812110378
Author(s):  
Timothy D. Stark ◽  
Ahmed K. Baghdady ◽  
Abdolreza Osouli ◽  
Heather Shoup ◽  
Michael A. Short
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Penetration Rate ◽  
Standard Penetration Test ◽  
Drilled Shafts ◽  
Penetration Test ◽  
Weak Rocks ◽  
Fine Grained ◽  
Linear Slope ◽  
Penetration Tests

Standard penetration tests (SPTs) have been used to estimate strength parameters of soils and weak rocks when it is difficult to obtain high-quality samples for laboratory shear testing. SPTs require 45 cm (18 in.) of split-spoon sampler penetration to determine the blowcounts per 0.3 m (1 ft), which is difficult to impossible to obtain in weak rock, that is, intermediate geomaterials. As a result, a modified SPT is presented here for sampler penetrations less than 45 cm (18 in.) in weak rocks. This new procedure is termed the modified standard penetration test (MSPT) and uses the penetration rate, not the sum of penetration blowcounts per 0.3 m, to estimate the unconfined compressive strength for the design of drilled shafts in weak fine-grained rocks. The penetration rate is the inverse of the linear slope of the penetration depth versus blowcount relationship. With this new test and interpretation procedure, 45 cm (18 in.) of sampler penetration is no longer required to estimate the unconfined compressive strength of weak rocks. An empirical correlation between MSPT penetration rate and laboratory-measured unconfined compressive strength is presented here for weak Illinois shale. This correlation could be used to estimate the unconfined compressive strength for the design of drilled shafts in weak rocks.

Field Testing: The Standard Penetration Test

1986 ◽  
Vol 2 (1) ◽  
pp. 21-26 ◽  
Author(s):  
S. Thorburn
Keyword(s):  
Field Testing ◽  
Standard Penetration Test ◽  
Cohesive Soils ◽  
Test Results ◽  
Penetration Test ◽  
Test Procedures ◽  
Weak Rocks ◽  
Fine Grained ◽  
Introductory Lecture ◽  
Strength And Stiffness

AbstractThis introductory lecture discusses the international use of the standard penetration test (SPT) and presents the proposals for International Reference Test Procedures. The application of the SPT as a means of assessing the strength and stiffness of weak rocks is mentioned together with the reliance upon the test at the present time for estimating the liquefaction potential of saturated fine grained non-cohesive soils. The various aspects of the execution of the SPT are discussed which can provide variable and unrepresentative values of resistance (N values).The principle of measuring energy losses and making adjustments to the N values is introduced as a basis for ensuring comparability of test results.Reference is made to the general descriptions of the SPT given in BS 5930:1981 and to the lack of clear guidance in this British Standard.

Evaluation and Quality Control of Dry-Jet-Mixed Clay Soil-Cement Columns by Standard Penetration Test

2003 ◽  
Vol 1849 (1) ◽  
pp. 47-52 ◽  
Author(s):  
Songyu Liu ◽  
Roman D. Hryciw
Keyword(s):  
Quality Control ◽  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Clay Soil ◽  
Soft Soil ◽  
Standard Penetration Test ◽  
Strength Characteristics ◽  
Penetration Test ◽  
Jet Mixing ◽  
Soil Cement

Dry jet mixing has been widely used since the 1980s for stabilization of soft soil. The quality and strength of the dry-jet-mixed columns must be evaluated to confirm the success of the stabilization. The standard penetration test (SPT) is shown to be a simple and effective method for this task. The strength characteristics along the length of the column were determined, and correlations between the SPT blow count and the unconfined compressive strength were developed.

Improvement of the Geotechnical Axial Design Methodology for Colorado's Drilled Shafts Socketed in Weak Rocks

2005 ◽  
Vol 1936 (1) ◽  
pp. 100-107 ◽  
Author(s):  
Naser M. Abu-Hejleh ◽  
Michael W. O'Neill ◽  
Dennis Hanneman ◽  
William J. Attwooll
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Design Methods ◽  
Drilled Shafts ◽  
Load Test ◽  
Empirical Methods ◽  
Weak Rocks ◽  
Rock Formations ◽  
Load Tests ◽  
Geotechnical Tests

Drilled shaft foundations embedded in weak rock formations support a large percentage of bridges in Colorado. Since the 1960s, empirical methods that entirely deviate from the AASHTO design methods have been used for the axial geotechnical design of these shafts. The margin of safety and expected shaft settlement are unknown in these empirical methods. Load tests on drilled shafts provide the most accurate design and research data for improvement of the design methods. Four Osterberg axial load tests were performed in Denver on drilled shafts embedded in soil-like claystone, very hard sandy claystone, and extremely hard clayey sandstone. An extensive program of simple geotechnical tests was performed at the load test sites, including standard penetration tests (SPT), unconfined compressive strength tests (UCT), and pressuremeter tests (PMT). Information on the construction and materials of the test shafts was documented, followed by thorough analysis of all test results. Conservative equations were suggested to predict the unconfined compressive strength and mass stiffness of weak rocks from SPT and PMT data. Colorado Department of Transportation (CDOT) and AASHTO–FHWA design methods for drilled shafts were thoroughly assessed. Design equations to predict the shaft ultimate unit base resistance ( qmax), side resistance ( fmax), and an approximate load–settlement curve as a function of the results of simple geotechnical tests were developed. The qualifications and limitations for using these design methods are presented (e.g., construction procedure, field conditions). Finally, a detailed strategic plan to identify the most appropriate design methods per LRFD for Colorado's drilled shafts was developed.

Modeling unconfined compressive strength of fine-grained soils: Application of pocket penetrometer for predicting soil strength

CATENA ◽  
2021 ◽  
Vol 196 ◽  
pp. 104890
Author(s):  
Fatemeh Mousavi ◽  
Ehsan Abdi ◽  
Shaaban Ghalandarayeshi ◽  
Deborah S. Page-Dumroese
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Soil Strength ◽  
Fine Grained

scholarly journals KUAT TARIK ANGKER KANTILEVER DENGAN METODE PENDEKATAN JRC (STUDI KASUS JALAN KANTILEVER KM. 461+480 TAPAKTUAN)

2018 ◽  
Vol 1 (3) ◽  
pp. 647-656
Author(s):  
Jumaidi Jumaidi ◽  
Munirwansyah Munirwansyah ◽  
Sofyan M. Saleh
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Safety Factor ◽  
Standard Penetration Test ◽  
Rock Quality Designation ◽  
Penetration Test ◽  
Loading Test ◽  
Rock Quality ◽  
Ground Anchor ◽  
Cut And Fill

Abstract: The Tapaktuan-Bakongan is the national road access to the South-West part of Aceh. Topographically shows that the road consist of canyon and a very steep cliff, which will be impossible to build more infracstructure using either blasting or cut and fill method with heavy equipment. Referring to the situation, the study about anchor tensile strength, which is used in construction of road access expansion using cantilever method is conducted. The research methode is begin by collecting the real data which are Standard Penetration Test data (SPT) SNI 4153-2018 and tensile graund anchor proving test (Bristish Satndard 8081:1981) and geological data taken from SPT drilling data. Furthermore, the data involved N-SPT, Joint Roughness Coefficient (JRC), shear stress will be analyzed and yield loading test value. Finally, from the loading test value, the reseacher will evaluate the stability of tensile capacity and safety factor (SF) of ground anchor. From the data analysis obtained that rock mass of STA 1+ 280 or KM. 461 +480 geologically contain unrigid and very strong limestone with N-SPT value greater than 50 where the rock condition is solid concrete and could be crushed using blasting method. Five samples are taken from the 10 meters driling for the laboratory test and obtain the minimum compressive strength is 51,10 MPa and maximum is 103,89 MPa with JRC from 2 to 20. In addition, the rock quality designation (RQD) calculation yield the average stone quality is 60,8% which means the rock has medium quality. Ground anchor failure if the proving test over 80% UTS(ultimate tensile strength)   i.e. the load increment reaches 92,55% UTS or 54 MPa. Therefore, the proving test maximum capacity for ground anchor is 54 Mpa and safety factor is 1,85 which are suitable to geological condition research area.Abstrak: Ruas jalan Tapaktuan – Bakongan merupakan ruas jalan nasional lintas Barat – Selatan Aceh. Kondisi topografi ruas jalan terdiri dari tebing yang terjal dan lereng yang curam sehingga tidak memungkinkan dilaksanakan pelaksanaan kontruksi pembangunan/peningkatan dengan metode blasting (penggunaan bahan peledak) maupun metode cut and fill yang menggunakan alat-alat berat. Dari permasalahan tersebut dilakukan sebuah kajian mengenai kuat tarik angker yang digunakan pada pelaksanaan pembangunan pelebaran badan jalan dengan menggunakan metode kantilever untuk daerah dengan kondisi topograsi tebing yang terjal dan lereng yang curam. Metode yang diterapkan pada penelitian ini diawali dengan pengumpulan data riil yang meliputi data Standard Penetration Test (SPT) SNI 4153-2008 dan uji tarik proving test ground anchor (British Standard 8081:1981) dan data geologi yang dihasilkan dari data pengeboran SPT. Selanjutnya dari data-data yang diperoleh dilakukan analisis data yang meliputi analisis nilai N-SPT, Joint Roughnes Coefficient (JRC), gaya geser, yang menghasilkan angka loading test. Dari data hasil loading test dapat dievaluasi stabilitas kapasitas tarik dan safety factor (SF). Dari data analisis didapatkan bahwasanya kondisi geologi batuan di STA 1+ 280 atau KM. 461 + 480 terdiri dari batu gamping tidak lapuk dan sangat keras dan dapat dipecahkan dengan peledakan dengan nilai N-SPT lebih besar dari 50 dimana kondisi batuan sangat padat. Dari hasil pengeboran sepanjang 10 meter diambil lima sampel untuk di uji laboratorium dan diperoleh nilai compressive strength minimal 51,10 MPa dan maksimum 103,89 MPa dengan nilai JRC 2-20. Selain daripada itu hasil perhitungan rock quality designation (RQD) menunjukkan kualitas batuan pada lokasi kajian rata-rata 60,8% yang berarti kualitas batuannya adalah sedang. Ground anchor putus pada saat uji tarik proving test diatas pembebanan 80% UTS yaitu pembebanan sampai 92,55% UTS (ultimate tensile strength) atau sebesar 54 MPa. Dengan demikian kapasitas maksimum hasil uji tarik proving test ground anchor yaitu sebesar 54 MPa dengan faktor keamanan 1,85 sesuai dengan kondisi geologi daerah kajian.

scholarly journals STRENGTH CHARACTERIZATION OF FOUNDATION SOILS AT FEDERAL UNIVERSITY LOKOJA BASED ON STANDARD PENETRATION TESTS DATA

2017 ◽  
Vol 36 (3) ◽  
pp. 671-676
Author(s):  
JA Sadeeq ◽  
AB Salahudeen
Keyword(s):  
Soil Properties ◽  
Estimation Method ◽  
Average Energy ◽  
Standard Penetration Test ◽  
Analytical Models ◽  
Penetration Test ◽  
Strength Characterization ◽  
Penetration Tests ◽  
Allowable Bearing Pressure

Strength characteristics of foundation soils in the Permanent site of the Federal University Lokoja in Kogi State were evaluated based on standard penetration test (SPT) results using some conventional analytical models proposed by different researchers. The study was carried out in order to take precise engineering decisions on the type of foundations suitable for the proposed structures and to determine the optimal depth of foundation embedment.  The SPT N-values were first corrected to the standard average energy of 60% (N60) before they were used to correlate soil properties. Evaluation of the soil properties were done at foundation embedment depths of 0.6, 2.1 and 3.6 m. Results show that bearing capacity generally increased with boring depth. Based on the Meyerhof allowable bearing pressure estimation method, foundation pressures in the range of 150 – 600  kN/m2 were evaluated for use in the study area at shallow depths (depths in the range of 0.6 - 3.6 m).http://dx.doi.org/10.4314/njt.v36i3.2

A method for correlating large penetration test (LPT) to standard penetration test (SPT) blow counts

2003 ◽  
Vol 40 (1) ◽  
pp. 66-77 ◽  
Author(s):  
Chris R Daniel ◽  
John A Howie ◽  
Alex Sy
Keyword(s):  
Wave Equation ◽  
Correlation Method ◽  
Standard Penetration Test ◽  
Penetration Test ◽  
Unified Approach ◽  
Equation Analysis ◽  
Gravelly Soils ◽  
Penetration Tests ◽  
Correlation Factors ◽  
Good Agreement

The standard penetration test (SPT) split-spoon sampler is too small for investigations in gravelly soils. For this reason, several researchers have developed scaled-up versions of the SPT, commonly referred to as "large penetration tests" (LPT), and attempted to correlate the measured blow counts to SPT blow counts. Several LPTs have been in use worldwide; each with different drill rods, sampler dimensions, and hammer energies; hence existing published LPT–SPT correlations differ for each system. This paper summarizes the LPT data in the literature and presents a fundamental method for predicting LPT–SPT correlations. The proposed method is based on wave equation analyses of SPT and LPT and considers variations in test equipment, penetration resistance, and energy. It is shown that the method provides a unified approach for assimilating the various published LPT–SPT correlations. Additional SPT and LPT data were collected at a sand research site to check the proposed method and to expand the LPT database. The observed and predicted correlation factors are shown to be in good agreement. The proposed correlation method will be useful as a logical framework for the comparison of LPT data collected throughout the world. Additional research will be required to extend this procedure to gravel sites.Key words: large penetration test, LPT, fundamental correlation method, wave equation analysis, grain size effects.

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