1、 翻译部分英文原文Self-boring pressuremeter permeability measurements in Bothkennar clay S. RATNAM , K. SOGA , R.J. MAIR and R.W.WHITTLE KEYWORDS: clays; earth pressure; in situ testing; permeability; pore pressures,site investigation INTRODUCTION These measurements were carried out as part of an ongoing res
2、earch collaboration between the Cambridge University Engineering Department(CUED) and Cambridge Insitu (CI). The project is centred on the development of a self-boring pressure-meter(SBP)system capable of measuring permeability as one of a number of fundamental soil properties from a single selfbori
3、ng test.The SBP of the Cambridge design was developed in the 1970s to carry out minimal disturbance in-situ tests on soil for obtaining high-quality in-situ strength, stiffness and horizontal stress parameters(Wroth & Hughes,1972). The same device can also be used to obtain an indirect estimate of p
4、ermeability from a dissipation-type holding test(Clarke etal. ,1979).This new method is referred to as the Mark II method (MKII);it allows for a direct measurement of permeability to be made in addition to the previously mentioned measurements using the same instrument (Ratnam etal. ,2001a).This dir
5、ect measurement uses a SBP device,and is distinct from self-boring permeameter tests(e.g.Leroueil etal. ,1992; Gourvenac etal. ,1999).The method has been previously tested both in stiff Gault clay near Cambridge(Ratnam etal. ,2000)and in an engineered cement bentonite cut-off wall on a contaminated
6、site(Ratnam etal. ,2001c).The Bothkennar site was chosen to further validate the feasibility ofthe MKII method,particularly in a soft clay deposit. This was possible because of the extensive assessment of permeability at the site (Leroueil etal. ,1992).In addition,these tests provided the opportunit
7、y to compare SBP test datausing a new non-linear method (Bolton & Whittle,1999) with data from previous investigations using conventional analysis. BACKGROUND The Bothkennar site,located between Edinburgh and Glas-gow and adjacent to the River Forth in Scotland, was established in 1987 by the Engine
8、ering and Physical Sciences Research Council(EPSRC)for research into soft clay engineering.Prior to its use for other research,the site was thoroughly characterised using the most sophisticated testing methods available at that time(Hight etal. ,1992). This was in addition to the initial investigati
9、ons conducted prior to the purchase of the site (Nash etal. ,1992). A series of SBP tests was conducted as part of the initial investigations. The tests were done by PM Insitu Ltd. and were at intervals of approximately 1 m to a depth of about 20 m,in a single borehole(PR1) near the south boundary (
10、see Fig.1).Permeability testing was not undertaken in these initial investigations. Subsequently,during the site characterisation studies,in-situ permeability testing was conducted by Laval University using their self-boring permeameter (PERMAC) and push-in piezometers, and by the Building Research
11、Establishment (BRE) using a pushed-in BAT system (Leroueil et al. ,1992). The characterisation study area is located to the north-west of bore-hole PR1in Fig.1.The PERMAC work was conducted in two boreholes(SBP 1 and 2) while five push-in piezometers(PZ1-5), pushed to depths of 3,6,9,12 and 15 m, we
12、re located in a north to south line,to the east of the self-bored locations(Hight et al. , 1992). The PERMAC testing was conducted at 3 m intervals between 3 m and 15 m using two test cavity aspect ratios at each test depth. The PERMAC instrument was with-drawn from the borehole in order to alter it
13、s test cavity aspect ratio( L = d ), which is a function of the cavity or pocket length, L ,and diameter, d .Interchangeable parts were used to give L = d ratios of 2 and 4 with this system. The PERMAC device is a purpose-built self-boring permeameter, which is capable of measuring only permeability
14、.Pressuremeter tests were therefore not made in these boreholes. Other types of testing and investigations at the site are discussed elsewhere(Hight etal. ,1992; Nash et al. ,1992),and will not be considered further here. Fig.1. Location of previousinvestigations(after Hight etal .,1992)SOIL PROFILE
15、 AND GEOTECHNICAL PROPERTIES Nash etal. (1992) report that the clay is generally uniform across the site apart from the south-east corner, where it is highly laminated (east of P18in Fig.1). The groundwater in the clay is hydrostatic, with the water table about 0.5 m below ground.Leroueil et al. (19
16、92) summarise and discuss some of the geotechnical index properties of the clay,and also the fabric profile at the site,that have some bearing on hydraulic con-ductivity (Fig.2).The moisture content has been noted to vary considerably both across the site and with depth (Nash etal. ,1992). While the composition of lithological units L2, L3 and L4 is considered to be relatively
