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HomeMy WebLinkAboutUntitled (2) FOLINDATIIIN, SLAB,ANI) .P,AVEMENT DISCUSSION AND R14"01‘INIEND;tellONS, Various foundation types h;totte heen considered for support (n'ilk proposed structure. 'Roo requirements muai he met in the design of finundations, first, the applied bearing stress must bc less than the ultimate bearing capacity (.4.`foundation soils to maintain stability, Second, total and differential settlement must nut ar; aillOtint that will produce en adverse behavior of the superstructure. Allowable settlement l,s usualf,„ estceeded before bearing capacity considerations become important: thus, allowable bearing pressure is normally controlled by settlement considerations. Considering subsurface conditions and the proposed construction, it is recommended that the structure be founded upon conventional spread footings and continuous wall footings. "fotal settlements should not exceed I inch if the following design and construction recommendations are observed, Foundation Design Recommendations Based on data obtained from the site and test results from various laboratory tests performed. MIT recommends following guidelines for the net allowable soils bearing capacity: Soil Bearing Capacity Footings must bear on competent, undisturbed, 2,000 lbstift native cemented sandy silt soils or compacted Not Required for structural fill. Existing lean clay soils and fill Native Soil A 1/3 increase is allowable II materials must be completely removed from for short-term loading, below foundation elements.1 Excavation depths . • - 95% for Structural Fill which is defined btm seismic ranging from 2.6 to 2.7 feet bgs should be events or designed wind anticipated io expose proper bearing soils.- speeds. •it will he required for NITI personnel to verify the bearit&soil suitability for each structure at the time el construction. Depending on the time of yea; construction takes place, the suhgrade soils may_be unstable beeau,,e of hill rnoistur, contents. If unstable conditions are encountered, over-excavaticm and replacement \Oft ttranular structural till andlor use of geotextile.,,,. may be required The following sliding frictional coefficient values should be used: I) 0.35 for footings bearing on native sandy silt (NIL) sediments and 2) 0.45 for footings bearing on granular structural fill. A passive lateral earth pressure of 335 pounds per square foot (nsf) should be used for sandy silt tN4L) soils. For compacted sandy gravel fill, a passive lateral earth pressure of 496 psf should be used, Footings should he proportioned to meet either the stated soil bearing capacity Or the 2012 I HI' minitriom requirements. 'fatal settlement should be limited to .approximately 1 Mull., and differential soden-teal shot Ii be limited to approximtnely incl•:, Objectionable soil types encountered at Mc bottom cii‘ es:cat:J.:Mons shoilld h' removed and 1'01)1:Iced kith Shut htnal co ;tvel loos,' tII' S411) It t( in the hi'time sul'igvacle will itectuire rreencxcevation and backbiting a Atli sinictitral oh I ihe thtforciiinl movement that mJ\, occur hocatie of vaniat.oieiii lefvii ' -sik ra, end s,cristi'inal moisture contem, 1\411 rectumnen& continuous loin ' . hiHithin=„ • I PeEC [1 to make them as es possible. Feia trost protection. the hottont Of external footings heuld be finished P)4 Slab-oni-Grade A thin veneer oil uncontrolled fill. xyllich contained sonic construction debris.. :,,,vas kid} IA-2Si 10CatienS. MII recommends that these till soils be excavated to a sulficiera ds:12th to expose cen:wetene native soils. NiT1 personnel mu5t he present during excavation to identifyThese materials. Native clay soils are moderately plastic and will be susceptible to shrinklswell movements associated with moisture changes. Areas of the site within the proposed structures should he excavated to sufficient depths to expose lean clay. The clay soils should be scarified to a depth of 6 inches and re-compacted between 92 percent and 98 percent of the maximum density as determined by ASTM 1)698. The moisture content should range from 1 to 4 percentage points above optimum. Structural fill should be placed as soon as possible after re-compaction of clay soils in order to limit moisture loss within the upper clays. Ground surfaces sliould be sloped away from structures at a minimum of 5 percent for a distance of 10 feet to provide positive drainage of surface water away from buildings. Grading must be provided and maintained following construction.. Organic, loose, or obviously compressive materials must be removed prior to placement of concrete floors or floor-supporting fill. In addition, the remaining subgrade should be treated in accordance will, .ilidelines presented in the Earthwork sectioll, Areas of excessive yielding should be excavated and hack filled with structural till. Fill used to increase the elevation of the floor slab should meet requirements detailed in the Structural Fill seetion. hill materials must he compacted to a minimum 95 percent of maximum denSity tt,; determined by ASINT D1557. A frec-draining.. granular Mal (drainage fill course) should be provided below slabs-on-grade. This should ac a minimum of 4 inches in thickness and properly compacted. 'The mat should consist of a void and gravel mixture, complyini2, with Idaho Standards for Public Works Construction (ISPW( ) specifications for (Type 1) crushed aggregate. A moisture-retarder should be placed beneath flour slabs to minimize potential ground moisture effects on moisture-sensitive floor coverings. The moisture-retarder should be at least 15nil in thickness and have a permeanee of less than 0.01 US perms as determined by ASTM [96. Placement t+1 the moisture-retarder will require special consideration with regard to effects on the slab-on-grade and should adhere io recommendations outlined in the ACI 302.1R and ASTM F1745 publications. Hie giant:hi alMl should be compacted to no less than 95 percent of maximum density' as determined by ASRID1557. Upon request. ATI] can provide further consultation regarding installation. Recommended Pavement Sections has made assumptions fur traffic loading variables based on die character of the proposed construi.miiii. lite client shall review and understand these assumptions to make sure they reflect intended usemil loti(itart of piin.iements both no‘ii.i and in the future. Rased on experience with soils in the l'etiOn. a snhgrailc elitorris Pcaring Ratio ( UR) value oi 3 nit, hecn ,issuniec1 for netr-:.-airlace lean clay soils on site h lerlicieine rri:nnntnil thiCkneSS rclu1yofl1it for assured I)cpending on conditions, seel prepara;ion. rriT: h required to support eni-artidion equipineni. I me:.Zi„ haVt2 SOP Stibgratic Soils ,aihsection. 1!!!!!!! !!! fitttitt ti I, 1111 r „ - - Flexible Pavement Sections The American Association of State illighway• and Transportation Officials (A,ASI-ITt..)) des:go method ft been used to calculate the following pavement sections, Calculation sheets provided in the Appendix indicate the soils constant, traffic loadiiig. trail-fie projections. and material constants tISeti 0: (-At-Hiatt' i.fir \C111. ii SeeriOUS. rym recommends that materials used ID the construction ot asphaltic concrete pavements, rneet requirements of the ISPWC Standard Specification for Highway Construction, Cow-arm:tit)a of frit: pavement section should be in accordance with these specifications and should adhere to guideline recommended in the section on Construction Considerations. AASHTO Flexible Pavement S ecifications . , . Asphaltic Concrete 25 Inches 3.0 Inches 1,1 Crushed Aggregate Base 4.0 Inches 6.0 Inches 11! b Structural - Subbase12.0 Inches 14.0 Inches Compacted Subgrade 95% of ASTM D608 95% of AS-1'Ni D698 • in will he required frit Mlli_personnel Luvei sutigrade competency at the time()I-construction. Asphaltic Concrete: Asphalt mix design shall meet the requirements of ISPWC. Section 810 Class III plant mix. Materials shall be placed in accordance with 1SPWC Standard Specifications for lirzhwati, Construction. Aggregate Base: Material complying with 1SPWC Standards tar Crushed Aggregate Materials. Structural Subban' Material should comply with the requirements detailed in the Structural Fill section of this report: except that the maximum material diameter is no more than -It the component thickness. Common Pavement Section Construction Issues [he suhgrade upon which above pavement sections are to be constructed must he properl:y stripped, Mspected, and proof-rolled. Proof rolling or suhgrade soils should he accomplished using a heavy rulther- tired fully loaded, tandem-axle dump truck or equivalent Verification of subgrade competence by Mt personnel at the time of construction is required. bill materials on the site must demonstrate the indicated compaction prior to placing material in support of the pavement section. Mill anticipates that pavornent areas will be subjected to nioderate traffic. Dependent upon the time of year construction takes place, shallow native lean clay soils may tend to pump and rut during compaction. Clay and silt soils near and above eptiniwn moisture contents may tend to pump. Pumping or soft areas must be removed and replaced \vith structural fill. IIll material ',And aggregates in tiuntiott of the pavement section must h compacted to no less than 95 tticiotnit oF the maximum (het: deniity as dem-Intact' ASTM 1)698 for flexible pnrelachts 'sit DIr rigid paycotcuN It c material placed as a paventent section component cannot be tested by useal elsnrita ih iesting methods, then compaction of that material must be approved by observed ppm rolling, Minor (leilecsions l'rem priiof rolling for flexible pavements are rillotkdble. lfteflectiole, from proof tollhT :•L!id. nat event ,tupport courses, should mum be JetsTint*.