2005 Løsning2005 engelsk - NTNU...

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Postadresse Besøksadresse Telefon +47 73 59 45 90 Side 1 av 8 N-7491 Trondheim Høgskoleringen 7a Telefaks +47 73 59 46 09 eksamenlosn2005_eng NTNU Fakultet for ingeniørvitenskap og teknologi Norges teknisk-naturvitenskapelige Faggruppe for geoteknikk universitet Note Topic: Solution proposal Examination Soil investigations December 2 2005 Consultant: Course responsible, associate professor Rolf Sandven Date: 29.11.2005 Signature: File: _________________________________________________________________________________ Task 1 Miscellaneous questions Questions: Answers: Max. score: What is meant by Geotechnical Project Class, and how does the Project Class influence on the extent of site investigations in a project? Geotechnical Project class: System used for classification of project category, dependent on the project complexity and risk level. The Project class ranges from 1 - 3, where 3 is the highest and most demanding class. The classification in Project class set the criteria for the extent of soil investigation. 2 Which factors related to equipment and procedures may influence the recordings made in a Cone Penetration Test with pore pressure measurements (CPTU)? Equipment: geometry and wear, influence of net area ratio, calibration of transducer, accuracy/measuring range of transducers, influence of temperature gradients, surface roughness. Procedures: Procedure for zero recordings, waiting time for temperature stabilization after ground insertion, saturation of pore pressure element prior to and during penetration, continuous/discontinuous stroke, deviation from standard penetration rate, clogging of porous filter, collisions with stones or other objects, overloading causing shift in zero values etc 3 An unconfined compression test performed on a cylindrical 100 mm high specimen gives a failure at 10 mm deformation and a corresponding load of 75 N. The area of the specimen was 23 cm 2 at the start of the test. How large is the undrained shear strength s u for this clay sample? How would you regard the sample quality from this information? The undrained shear strength = s u = σ 1 /2, where σ 1 = P f (1- ε )/A P = 75 N A = 23,2 cm 2 ε f = 10 mm/100 mm = 0,1 σ 1 = 75(1- 0,1)/23.2 = 29,35 kN/m 2 s u = σ 1 /2 = 14.7 kN/m 2 The failure strain is defines at 10 %, which is high, indicating a somewhat disturbed sample. (Completely disturbed samples will have a defined failure strain of 15 %). 3 How can the sensitivity S t of clay be determined? Which property of the clay does this parameter express? Sensitivity: Falling cone apparatus in the laboratory (S t = s u /s r ). Vane test (directly: S t = s uv /s rv ) and CPTU (indirectly using sleeve friction recordings) in the field. The sensitivity expresses the loss in shear strength of the clay after remoulding. 2 Which factors influence the Material factors: Water content, grain size distribution,
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