Geotechnical Materials - Filter Materials

To obtain an efficient well for groundwater monitoring or abstraction, an important consideration is the filter material surrounding the well liner.

Washed, bagged and dried filter materials are available either as natural silica sands or "NEW" Glasmedia™ made from recycled glass; both are ideal media for this purpose. There functions are to allow largely unrestricted flows of groundwater into the well while simultaneously preventing the ingress of soil particles (other than those during the initial development phase) and supporting the water-bearing formation.

Informed judgment must be made regarding the wellscreen slot sizes, the filter material and the encountered ground conditions to obtain the correct borehole construction.

Silica Filter Sands - These materials from non-substainable materials are available in graded sizes as in the tables below:

Size	Weight	Part Number
0.5 - 1.0 mm sand	x 25 kg	SWSFS1
1.0mm - 2.0 mm sand	x 25 kg	SWSFS2
2.0mm - 5.0 mm	x 25kg	SWSGM3
3.0mm - 6.0 mm	x 25 kg	SWSFS4
10mm Single Size	x 25kg	SWSFS5

Industrial Dried Silica Sands

British Sieve No	0.5 - 1.0 mm	1.0 - 2.0 mm	2.0 - 5.0 mm
4	-	-	96.2
5	-	-	83.4
6	-	-	56.4
7	-	-	31.2
8	-	98.3	6.9
10	-	78.6	2.6
12	99.8	52.3	-
14	98.7	27.0	-
16	74.5	6.0	-
18	44.8	0.2	-
22	15.2	-	-
25	4.9	-	-
30	0.6	-	-

The NEW Glasmedia™

Glasmedia^™ is manufactured from sustainable recycled material container glass (graded silicate glass sand) in the United Kingdom and diverts unwanted glass from being landfilled. During the manufacture the recycled glass is imploded using ultra sonic sound waves to produce a smooth particle shape that is not sharp; you can actually rub it in your hands quite safely. The glass particles are washed to ensure they are clean and free from contamination from their previous use. The Glasmedia™ is hot air dried and graded in to 25 kilogram recyclable plastic sacks.

"Glasmedia™ is carefully graded to produce a wide range of suitable filter and back fill media both for use within monitoring boreholes, water wells and for back filling in geothermal installations".

Percentage Passing

Glasmedia™
Percentage Passing
Mesh mm	swsgm2 (1.0 - 2.0mm)	swsgm3 (2.0 - 5.0mm)	swsgm4 (3.0 - 6.0mm)	swsgm5 (6.0 - 10.0mm)
1.0	4.90
1.3	41.70
1.4	70.40
1.6	93.00
2.0	100.00	1.70
3.0		23.40	4.28
4.0		68.20	50.70
4.5		91.00	76.40
5.0		97.00	83.50	0.00
6.3		100.00	100.00	14.00
7.1				57.10
8.0				77.40
9.0				88.80
10.0				99.00

Glasmedia™ is able to offer the additional benefit of contributing significant quantities of recycled materials during the development of new buildings with geothermal installations and during dewatering works, this benefit should be highlighted with your tender submissions as it may just tip the contract in your direction. For example if you are installing 10 No. 32mm loops to 100metres within a 6” drilled well with Glasmedia™ installed to 10 m bgl, this would equate to the use of 23,000 kilograms of recycled materials.

Size	Weight	Part Number
0.5 - 1.0 mm sand	x 25 kg	SWSGM1
1.0mm - 2.0 mm sand	x 25 kg	SWSGM2
2.0mm - 5.0 mm	x 25kg	SWSGM3
3.0mm - 6.0 mm	x 25 kg	SWSGM4
10mm Single Size	x 25kg	SWSGM5

Additional benefits of the "New" Glasmedia™ is that the silica content is in a bound form and provides no health risk and the product is less dense than conventional filter sand so less materials are required to back fill the annulus. The Table below indicates the bags required to back fill with assuming no voids within the drilled hole quanity of filter materials:

Please request samples from Kevin Neat.

Quantity of Glasmedia™

Drilling Dia			Well Lining Dia			Approx number of 25kg bags per metre
6"	150	mm		19	mm	1.04	bags
	150	mm		35	mm	1.00	bags
	150	mm		50	mm	0.94	bags
8"	200	mm		50	mm	1.74	bags
	200	mm		100	mm	1.39	bags
	200	mm	6"	150	mm	0.80	bags
10"	250	mm	4"	100	mm	2.53	bags
	250	mm	6"	155	mm	1.87	bags
	250	mm		200	mm	1.14	bags
12"	300	mm		100	mm	3.79	bags
	300	mm		155	mm	3.13	bags
	300	mm		200	mm	2.40	bags
	300	mm		250	mm	1.26	bags
14"	350	mm		100	mm	5.29	bags
	350	mm		155	mm	4.63	bags
	350	mm		200	mm	3.90	bags
	350	mm		250	mm	2.76	bags
16"	400	mm		155	mm	6.43	bags
	400	mm		200	mm	5.70	bags
	400	mm		250	mm	4.56	bags
	400	mm		300	mm	3.30	bags

Geotextile Filters for Wellscreens

Installation of well liners when all ground conditions are unquantified still presents problems due to fine sands and silts that may be present. There is the risk that these will migrate into the well causing it to silt up with the associated costs of redrilling.

A practical solution to this common problem is the use of geotextiles which are applied over the slotted well liner after machining into a tube. The benefits of the geotextile allow for the unexpected that can be encountered during site investigations.

The geotextiles are highly chemical resistant with a high tensile strength and a high transmissivity.

Available in a range of sizes and manufactured to fit any pipe size from 19mm to 630mm diameter.

Geotextile Filters Specifications

Part Number	D85	D150	D200	D260
Pore Size	85	150	200	260
Weight g/m2	140	125	160	130
Thickness (mm)	0.95	0.97	1.00	-
CBR Test	1335	1500	n/a	2000
Fall Cone Test	32	28	n/a	12
Water Permeability ltrs/second/m2	10 150	n/a 100	48 x10 180	48 x10 45
Specific Weight	0.90	n/a	1.30	1
Trade Name	F-2B	TER 1000	GEOSOCK	HF-400

An outer protective netting can be fitted to protect during transportation and installation within the borehole.

Email Us or call 01953 454540 for more information