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HomeMy WebLinkAbout70372; Elm Avenue South Slope Improvements; Elm Avenue South Slope Improvements; 1986-08-28Testing Engineers — San Diego Mailing Address: Post Office Box 80985 San Diego, CA 92138 3467 Kurtz Street San Diego, CA 92110 (619) 225-9641 GEOTECHNICAL CONDITIONS SOUTH SLOPE IMPROVEMENTS ELM AVENUE CARLSBAD, CALIFORNIA CITY OF CARLSBAD JOB NO. 70372 AUGUST 28, 1986 Testing Engineers — San Diego Mailing Address: Post Office Box 80985 San Diego, CA 92138 3467 Kurtz Street San Diego, CA 92110 (619) 225-9641 August 28, 1986 Job No. 70372 City of Carlsbad 2075 Las Palraas Drive Carlsbad, California 92008 Attention: Subject: Mr. Mark Gibson Geotechnical Conditions South Slope Improvements Elm Avenue Carlsbad, California Gentlemen: In accordance with your request, we have investigated geologic conditions of the existing roadside cut slope south of Elm Avenue in Carlsbad, California. The portion of Elm Avenue investigated is shown on Plate 1. The investigation consisted of an inspection of the exposed cut slope and surrounding geologic features, selected laboratory testing to aid in unit classification, and the use of a seismic refraction survey to give an indication of the rippability of materials likely to be encountered during the planned improvements. The details of the investigation and our findings are presented herein. City of Carlsbad Page No. 2 August 29, 1986 Job No. 70372 SITE EXPLORATION The subject site was inspected by a geologist from our office who conducted slope measurements, identified exposed geologic units, and noted conditions which would give an indication of slope stability in its present configuration. Seven soil samples were obtained at the site, and the locations are indicated on Plate 1. Sieve analysis was performed on selected samples in order to confirm unit classifications made in the field. All units were classified according to the Unified Soil Classification System as presented on Plate 2. A description of the samples taken is given in Plate 3. A seismic refraction survey was conducted by Mr. Ted Funnekotter, Certified Engineering Geologist, at the request of Testing Engineers. The seismic refraction survey was designed to measure the velocity of sound within the near surface geologic section. These seismic velocities give an indication of the expected ease of excavation. Two seismic lines were run at the subject site. The first was approximately four-hundred and fifty (450) feet long and ran parallel to, and ten (10) feet south of the present top of the City of Carlsbad Page No. 3 August 29, 1986 Job No. 70372 cut slope. The second line ran for one-hundred and fifty (150) feet along the western end of the first bench. The location of these lines are shown on Plate 1. Details of the seismic refraction survey, rippability-seismic velocity relationships and survey limitations are presented in Appendix A. SITE CONDITIONS The existing Elm Avenue cut slope is at a grade of approximately 1.5 to 1, horizontal to vertical. A profile of the existing slope is shown in Plate 4. Exposed along the cut slope is massive silty and clayey sandstone, apparently Eocene marine deposits of the Santiago formation. The exposed sandstone is white to tan-gray, fine to coarse grained with variable fines, weathered, and in a friable condition. No exposures of the Cretaceious igneous granitic or metavolcanic units common to the general area were observed at the subject site. City of Carlsbad Page No. 4 August 29, 1986 Job No. 70372 Numerous tension cracks are present in the existing slope. The cracks are generally five (5) to ten (10) feet in length and run perpendicular to the dip of the slope. The general topography of the cut slope indicates that creep and/or small scale slumping has occured. Numerous trees on the slope display bowed trunks, suggesting possible slope movement. These conditions indicate some slope instability in its present configuration. The seismic refraction survey indicates the presence of up to three distinct seismic velocity zones within the existing slope. The first and slowest of these has velocities ranging from fifteen hundred (1500) to two thousand (2000) feet per second, and probably represents a moderately to heavily weathered two (2) to nine (9) foot thick near surface section along the existing slope face and upper mesa. The second and third velocity zones have velocities ranging from twenty-five hundred (2500) to twenty-seven hundred (2700) feet per second, and from thirty-three hundred (3300) to forty-three hundred (4300) feet per second, respectively. The transition between these two zones lies at an elevation of between two-hundred fifteen (215) and two-hundred thirty (230) feet above sea level, and has a gentle westerly apparent dip. These two zones City of Carlsbad Page No. 5 August 29, 1986 Job No. 70372 appear to represent broad, largely similar sandstone units with slight differences in cementation, fracturing, and content of fine grained material. The range of seismic velocities encountered, fifteen hundred (1500) to forty-three hundred (4300) feet per second, suggest that all of the materials encountered during the planned W.W-.^,improvements; should*, be rippable using a D-9 dozer or equivalent. <SSa. -' No velocities were encountered which would indicate the presence of hard, igneous or metavolcanic units. However, a small possibility does exist that such units could be present in areas outside the detectable zone of the seismic lines surveyed. CONCLUSIONS AND RECOMMENDATIONS 1. Materials to be excavated during the planned improvements should be rippable using a D-9 dozer or equivalent. City of Carlsbad Page No. 6 August 29, 1986 Job No. 70372 2. Existing slope conditions indicate some slope instability at the present 1.5 to 1, horizontal to vertical, slope configuration. It is therefore recommended that the new slope should be no steeper than a 2 to 1, horizontal to vertical slope. A bench should again be^placed approximately half way up the new slope. 3. Erosional rilling can be a problem in sandstone units such as those at the subject site. For this reason, drainage swales should again be placed at the mid-slope bench and at the top of the new slope. ^^ 4. The new cut slope should be landscaped to minimize the possibility of erosion and maximize slope stability. INVESTIGATION LIMITATIONS The materials encountered on the project site and utilized in our laboratory investigation are believed to be representative of the total area. However, soil and bedrock materials vary in characteristics between excavations and natural outcrops. City of Carlsbad Page No. 7 August 29, 1986 Job No. 70372 Since our investigation is based on the materials observed, selective laboratory testing and engineering analyses, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice and no warranty is expressed nor implied. The opportunity to be of service is sincerely appreciated, and if you should have any questions, or require clarifications, please feel welcome to contact our office. William M. Schill Project Geologist SMP/WMS/kac Respectfully submitted, TESTING ENGINEERS-SAN DIEGO Stephen M. Poole, RCE 40219 Geotechnical Department Manager 'Q O O o o o o AVENIDA DE ANITA CONCRETE SWALE-BENCH ^-CONCRETE SWALE EXPLANATION SAMPLING LOCATION \. SCALE: l"=60' Testing Engineers-San Diego ELM /AVENUE IMPROVEMENT AREA Job No.: 70372 Date: 9/1/86 Plate: Testing Engineers-San Diego UNIFIED SOIL CLASSIFICATION r30 10 PLASTICITY CHART 0 TO 20 30 40 50 60 70 80 90 100 s-in 0> QJ'tn OOCM 6 to Z 5|cn £ O o> UJ O* 2 o 2-2 sillCC 0< EO _o o "5.e c0JC 0> o2 GROUP SYMBOL GW GP GM GC SW SP SM SC TYPICAL NAMES Well-groded grovels, grovel-sand mixtures, little or no fines Poorly graded grovels, grovel -sand mixtures, little or no fines Silty. gravels, gravel- sand-silt mixtures Clayey grovels, grovel sand-clay mixtures Well-groded sands, gravelly sands, little or no fines Poorly graded sands, gravelly sands, little or no fines Silty sands, sand- silt mixture Clayey sands, sand- clay mixtures >in O0CM 6Z e 0 O —tn oo 6UJ «> CC "° UJ a? eu. — "5 co a> o GROUP SYMBOL ML CL OL. MH CH OH Pt TYPICAL NAMES Inorganic silts and very fine sands, rock flour silty or clayey fine sands, or clayey silts with slight plasticity Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty cloys of low plasticity Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts Inorganic clays of high plasticity, fat cloys Organic clays of medium to high plasticity, organic silts Peat and other highly organic soils NOTE: DGroup symbol presented in SYMBOL column on BORING LOG. 2)The A line is on empirical relationship established by A. Casogronde. PLATE -L City of Carlsbad August 29, 1986 Job No. 70372 SOIL SAMPLES % Passing, Sample Number Description 200 Sieve Silty and Clayey Sand, white to tan-gray, fine grained sand, some 32 coarse sand, friable, dry to moist. Silty and Clayey Sand, white to tan-gray, fine grained sand, friable 15 dry to moist. Silty and Clayey Sand, white to tan-gray, fine to coarse sand, well 14 graded, weathered, friable, dry. Silty and Clayey Sand, brown to gray, fine to coarse, well graded, 23 weathered, friable, dry. Silty and Clayey Sand, white to gray, fine to medium grained sand, highly cemented, part of more resistant cemented plane with strike 25° W of N and dip 80° to NE. Silty and Clayey Sand, light brown to gray, fine sand, weathered, 35 friable, dry. Silty and Clayey Sand, white to tan with some red, fine sand, cemented, 20 friable, dry to moist. NOTE: Sampling locations are shown on Plate 1. Plate 3 o o o o o o o o o o o A 225- 200- LU LJ 175 CONCRETE SWALE- CONCRETE SWALE- PROPOSED CUT AT 2.-1 SLJOPE WEATHERED ZONE- FORMATIONAL SILTY 3 CLAYEY SANDSTONE SCALE: V'=20' Testing Engineers^San Diego PROFILE A-A Job No.70372 Dale, 9/1/86 T Plate-. ! ' 4 ! ./AY' APPENDIX A T. FUNNEKOTTER REGISTERED GEOLOGIST CERTIFIED ENGINEERING GEOLOGIST P. O. BOX 575 - ESCONDIDO, CALIF. 92025 746-2793 ENGINEERING GEOLOGY SEISMIC INVESTIGATIONS For Subdiviiion D*iign Pipelinet • Roodt Seitmic fiippobilify Sludiel O O O O SUBSURFACE INVESTIGATION O ELM AVE SOUTH SLOPE IMPROVEMENT CARLSBAD, CALIF. AUGUST 11,1986 O O O O T. FUNNEKOTTER REGISTERED GEOLOGIST CERTIFIED ENGINEERING GEOLOGIST P. O. BOX 575 • ESCONDIDO, CALIF. 92025 746-2793 ENGINEERING GEOLOGY SEISMIC INVESTIGATIONS For Subdivision Detign Pipeline! • Roodi Seitmic Rippobility Studi»t 1 PURPOSE: To evaluate subsurface conditions along select lines of a proposed street improvement in order to provide design and excavation information. METHOD: Refraction Seismography. Geologic reconnaissance. DISCUSSION: The composition of the site appears to be mainly sedimentary - silty and clayey sands and minor cobbles. To the east on the higher ridges igneous extrusives and intrusives are present. Two Seismic traverses were run on the site - located approximately as shown on the enclosed plat. Line A was run westward 10 feet south of top of slope - B was run on the south side of the first bench. These lines were placed on the only accessible places where the ground is least disturbed and closest to the proposed cuts. Most of the area of interest has been subjected to grading and trenching - this disturbance creats soffe,surface areas and limits the Seismic method to some extent(mainly the depth of penetration of the waves). Flags were placed every 150 feet along the lines for reference. Two to three velocity layers were encountered, i.e., 1500 to 2000 ft/sec, 2500 to 2700 ft/sec, and 3300 to 4300 ft/sec. All of these layers appear to be some variation of silty and clayey sands(see exposed cuts). Very small amounts of cobbles are noted. Depth of penetration is from 35 to 62 feet(this is the maximum penetration line). This line is the greatest depth of known conditions. No high velocity material(over 5500 ft/sec) was encountered on any of the runs. CONCLUSION: The Seismic results indicate no material velocities over 4300 ft/sec - most is under 3900 ft/sec. This material extends from 40 to 62 feet deep on line A and 35 feet on line B. For additional Seismic-rippability information see attached sheets. , /?- // Submitted by C^^^^^/^L T. Funnekotter t* O O O O O O O O O O ./I = loo mi:rrrrrpr - T. l-'UH.KEKOT SEO;STJ?ED GEOLOGIST CESTIF'ED £NG;M££!!NG GEOLOGIST P, O. SOX 575 • ESCONDIOO, CALIF. 92025 746-2793 GCOLOGY SEiSMIC I For Wp*(ln«s Soismlc Boodt ty Stvd'»« SEISMIC - RIPPABILITY INFORMATION The following points should be considered when evaluating Seismic information: 1. All velocities, depths, and thicknesses are averages and qualified as follows: G - good F - fair P - poor VP - very poor ? - questionable Grades of G, F, and P should be considered reliable; VP and ? should be considered as indications only. 2. Each profile provides information in the immediate area of that profile - extrapolation outward from this line must be considered speculative. In other words a velocity cross section is given along a specific line of investi- - gation - 10 to 20 feet from this line the conditions could vary. In order to avoid any surprises between the Seismic lines additional Seismic lines would be in order. 3. As the velocity of material increases, ripping becomes progressively more difficult until at some point it is more economical to drill and shoot the material prior to excavation. . Rippability also varies with the type of _,. , , ^?*~~*^f^a»»**s*^.<ss*a>m«a*x**^^material; however, in general, D-9 Cat single ripper per= ^""--fc_ _ * * O * .-_™«r^2BSl"ijS8^'*'JPKS£*v:K5^*ffi^^l^ows^r^rfpp^DTTTo 5000 ft/sec, ^-fcfr-^^VBa^^J**^/K3!aas^^ '5^«4eSt:S3^^~w^l£^^. 5500 ft/ sec. The changeover from- a ripping^to ^a^la sr ilvg - ***1"Wll!*&3si£S««»i&^ T1 • 1 » . 1 <ioperation usually occurs within the marginal zone. To determine rippability is essentially an economic decision - whether to continue ripping at higher velocities or to blast at lower velocities depends on the type of job, type of equipment, expertise of the operators, amount of excavation, how the rock is to be disposed of, time factor, etc. For example, in fractured rock a trench type of •operation is more difficult than a hillside job, especially if boulders are present. In a trench manuverability of the heavy equipment is limited and rock disposal is a bigger problem. The degree of fracturing is a factor in determining rippability, i.e., more fracturing,' lo.wer velocities, „r *T . J \ 4»iS2ii^2a--i~^sa:i^I-2^Y';s:as**easier ripping. The ,.same,.velocity««,coiilvd^r.epr-es£nt either^j^^&^^^^&s^-^r «**5»«^--3*^-^f«"^^decomposed or fractured rock. T. FUN NEK OTTER REGISTERED GECIOGIST CERTIFIED ENG'NEESISG GEOLOGIST P. 0. BOX 575 • ESCONOIDO. CALIF. 920J5 746-2793 ENGINEERING GEOLOGY SEISMIC I Subdivivion Dctign Pip«lin«t • Room iwnic Rippobiliry Stvdi O O O O O O O 4. 6. SEISMIC - RIPPABILITY INFORMATION Boulders are identified as scattered boulders (SB) , many boulders^ (MB) , and large boulders (LB). These notations can also mean, hard angular blocks. • ,Lajrg,e boulders are considered to be over !jQLf£gJL«i!i*diameter and"°lfven possibly to 30 feet in diameter,..--• ^-** f "~ «^^—« * J ^**autsaa£&&Iix&t^^ For trenching operations ,thj=r,ip,pability figures mus-t,O f p*"-?^'^*^™-^"4^-"^^^^^^ i=ad,jjuj.tjdmodovm^rdi,J41. e. , velocities as low as 3500 ft/sec may indicate difficult ripping depending on the degree of fracturing of the rock. Fractured rock and even small boulders can be very troublesome in a narrow trench. For example, decomposed granite ..is...easier,, to .~ ' ^aa*x~—i-t-C—. ~-^^-«^»Wjjju^-toeB*.JSji»u.^^ra.«^J^-»^^-^K.;«^«'^;s4<ajs,i;^ similar. ~ However ;~~iri" general, based on a machine com- *J*2&»3tJlS?jii*ji_^. -- . . rr-,1' EC=s^Je;2afeMSS:TE2CEC2^KS1a'^3fflSS2lE^^^.'E2K'parable to a Kohring_505 most .m^erajl^^^h^e^lp^i^ of approximately •3'8rQO^ftr/secjor^eAS^ou^b^r^E.gable, g*;^r%-jf .i.'m^-,-^f. ^~c~f*'-'''^~~I"V"-^ -.-• — ---"-v"*""-^^^"^"^- - K.«—•,-«i.s™Slv.w».-"'n «• »!-•*•-*-J>j' •—J*1-^...,- -I-.V.t.„-A.i, «ij-tfW,«•»*—•''''(Pra-*--*«*^es,A,«.ija^Aj*';,iSs;f^oyer ^SOQ^rt/^^c'^npn^rip^p^ble, and marginal in between.^ ^in^^h*aifr^^r^cin^"a""c"6"nditi6n of many boulders can be almost as troublesome as solid rock so the above figures should be used with discretion. Reader is cautioned that the Seismic traverse_s_glve_a_picture ia_Lonj the alignment only^jjsee^ Jjr^ai^r^^j^im^er^^^ 'a7e^Q*eTer=mined°*°by €fiW^lTenT^('o7°*cb7°THe=ccost ^pf §,ame). While a f ev^S^^l^niflel^a of the obvious nature of the subsurface (for example, in an area of large cuts where the subsurface profile is apparent along the cuts) in other areas many lines may not fully evaluate the subsurface picture because of its complexity and even more lines or drill holes or trenches may be in order. In other words, the techniques available now can be used to increase the amount of subsurface knowledge and only that - rarely will these methods give a completely accurate picture. There j^illalways be a certain degree of guesswork necessary "wnT&h "' ""' *'~ V^ •™**~*™™^''ii^L'|i!''g-'<i««a~«g!;CTT*'a*sa^ » _.., . . •™,._^«^.«pawill vary with the comuleteness ©f^tne invest^rg-atroYf? O O T. FUNNEKOTTER ENGINEERING GEOLOGY SE.SM.C INVESTIGATIONS REGISTERED GEOLOGIST For CERTIFIED ENGINEERING GEOLOGIST . Subdiviiion D*»ign P. O. BOX 575 - ESCONDIDO, CALIF. 92025 Pipeline* - Roodi 746-2793 Saiwnic Rippobilify Studiei RIPPABILITY SCHEDULE The following schedules should apply for the type of material encountered in this report: Based on a D-9 Cat Velocity (ft/sec) Excavation Method 0 to 2000 Scrapper 2000 to 5000 Ripper 5000 to 5500 Marginal Over 5500 Drill & Shoot For trenching, based on a Kohring 505 Velocity (ft/sec) Excavation Method 0 to 3800 Ripper 3800 to 4300 Marginal Over 4300 Drill & Shoot