Question

Please see picture below for question #1, parts a-d. Do you agree with my answers ?

a. 25 borings seems like enough for a 100' x 100' building, that's 4 every 25ft.

b. Borings are only 20 feet, I feel like this should be deeper for a 3-story building on poor soil. I would bore to 40ft.

c. If the number or depth of borings seem inadequate, as does the depth of the borings, I'd have them done to a deeper depth. Because the soil is in poor condition, I'd like to see what is down deeper as I may need to dig pilings.

d. I believe dewatering will be necesary as the soil has abundant sand with clay and clayey sand, which does not let go of water well.

1. (1 point) You are investigating a 100x 100' 3 story building site, poor soil conditions. Spread footings at 5 foot depth. Utility trenches will be a maximum of 10 feet deep. The boring logs provided by the Engineer show 25 borings. Boring Log B-1 by Terracon on the 2 page of this homework is typical of the borings. Show all your calculations and graphics necessary to justify answers. a Does the number of borings made during the design appear adequate? Explain. b. Does the depth of the borings appear adequate? c. What would you do if the number or depth of borings appears inadequate? d. Will dewatering of the site be necessary? Explain. 8.1 LOG OF BORING NO. B-1 Page 1 of 1 LENT COALITION FOR THE HOMELESS SITE 630 W. CENTRAL BOULEVARD PROJECT ORLANDO ORANGE COUNTY, FLORIDA COALITION FOR THE HOMELESS DESCRIPTION GRAPHICLOS TAS Sans Approx Surface Elev: 1055 SAND ne light grey SAND WITHICLAY 1803 CLAYFYSAND il gray, win some orange matting very 105 SAND WITHICLAY gray SP 5 13 light gray,medium dense SP & SS 22 SP 7 SS16 BORING TERMINATED AT 20 FEET The boundary in Automatically amer

Answer 1

1. To decide Spacing's of Bore hole, usually as per Thumb Rule, For small buildings, site covering an area of about 0.4 hectare (i.e. 4000 m² /43000 SQFT), one bore hole or trial pit in each corner and one in the centre (i.e. 5 boreholes in all) should be adequate. by this rule the 25 bore holes for 10000 SQFT is much higher. For Multi storied buildings generally spacing between bore hole is 10m (30ft) to 30m(90ft) depending up on the Variation in the subsurface condition or variation of strata in horizontal directions.
2. Normally the depth of exploration should be taken 1.5 to 2 times the estimated width of the largest footings (single or combined), from the base level foundation; but in weak soils, the exploration should be continued to a depth at which the loads can be carried safely (generally up to the hard stratum).It will difficult to say the depth of borings .It should be decided on Site.
3. Yes, you can go for deeper depth to get greater information regarding soil condition is achieved and hence the foundation design would be more cost effective. The possibility of encountering unexpected soil condition is reduced .
4. Clay always have greater affinity to water. It is always to have dewatering technique. however ,based on amount of water generated during exploration type of dewatering technique to be adopted