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HomeMy WebLinkAbout17413-3 WOODCREST DR_ 296-89 (30) 17413-3 WOODCREST PC# 296-89 30/32 Line 2 was conducted east-west up a steep hill Bedrock is expos at the . bedrock (4220-5380 !t/sec). p 0-2500 it/sec Readily rippable perpendicular to foliation. Line 2 is rather simple with south end of the line. 2500-4000 Ri most of the surface covered with weathered bedrock. The 10 p Difficulty with Little Line 7 was also in an existing cut elope, about -. Difficulty bedrock velocities range from 4000-5000 !t/sec. feet below natural grade on a fresh rock surface. Some of 4000-6000 Rippable with Considerable Line 3 was along a ridge-top about 60 degrees off of the undisturbed rock shows velocities on the order of 6000 Difficulty foliation. The surface is covered with weathered and less 6000-8000 Rippable with Great !t/sec with weathered material around 3950-4820 it/sec. A r Difficulty weathered bedrock with velocities ranging from 3750-5000 wedge of broken rock with low velocities is present near Blasting may be Required ft/sec. There are somewhat contradictory data, but there the west end of the line. 8000- Blasting generally required [_ is the possibility of a hard knob near station 75 with CONCLUSIONS Small areas of high velocity rocks, less than 20-30 velocities on the order of 7000 it/sac; most bedrock is It feet wide, such as knobs, dikes, or resistant lenses, may General i. about 5500 ft/sec at depths of lose than 15 feet. The determination of rippability is an imprecise go undetected in this survey. Seismic velocity may Line 4 was surveyed along a ridge underlain by science. Standard references such an those of the gradually increase as the hard rock is approached and resistant, rather massive rock. This shows a thin layer of Caterpiller Company have attempted to correlate excavation difficulty may increase significantly before I- weathered rock thickening somewhat east of station 120. rippability with compressional seismic wave velocity; all the actual horizon is reached. The bedrock is hard with velocities of 6450-7500 ft/sec of these studies are empirical in nature (a typical Rippability is best determined on a site to site Teasing somewhat to the east. example is attached). In addition to the seismic l basis using seismic velocities a3 a guide for field throughout Line S was located In an existing out where about 40 velocities other factors contribute to the actual testing ease of excavation at various locations throe g feet of rock had already been removed and was on a fresh rippability. These include: fracture density and the site. The seismic data applies to the immediate ` rock surface. The east end of the line shows near surface spacing, thickness of beds, type of equipment used, vicinity of the line only. I_ hard rock with velocities of 6190-6980? ft/sec. These t material type, skill and experience of equipment operator, Local T velocities lucre*se somewhat to the west where there is and geologic configuration of the material to be moved. l Hared on Lines S and 7 which were conducted on cut also a wedge of broken roc_. overlying the undisturbed Thus any formulation of a rippability chart must, by t surfaces the current equipment appears to be readily f material. necessity be very generalized. The following correlation ripping material with seismic velocities of 6000-6200 l Line 6 was along the ridge above the cut on Line S. can oaten be applied: l !t/sec and perhaps as h:Sh as 7000 ft/sec. However, any It is a simple line with a thin layer of low-velocity s area with seismic velocities over 6000 ft/sec should be ' material such as soil overlying a moderate-velocity j �- -- considered as a potential rippability problem (with or 1 l without blasting) and other factors such as the nature of ' AILAND ASSOCIATES,INC. NYLAND ASSOCIATES.INC. NYLAND ASSOCIATES,INC. 7k. ylj i T i : M _ = € � VW � I - APPENDIE C BEIBNIC REFRACTION BURVEY I. i18�Ntlp1�1 � aqe • RUM .� ■ 1 � a '' E A. The attached Seismic Refraction Survey Report addresses a f a W= ��\ € number of traverses (lines) completed within the Tuscany B� saNs�sllm y.ae•p \ W Hills Development. only lines S-1, S-2, S-3, and S-4 are I � within the area covered by this report. �\ \ B. The attached Tables A and B are compilations of all previous seismic refraction surveys conducted by other consultants ` \ 1 within the Tuscany Hills Development. The tables were r X a /\ \\ S prepared by GeoSoils, Inc., dated September 21, 1988, W.O. [ c 180-A-RC. For your convenience, all seismic refraction traverses conducted by other consultants, which lie within °n 1// o Parcel 5, have been shown on the Geotechnical Naps, Plates 1 1. 4 s /� S. d \ � s and 2, which accompany this report. / \ em /�/ m � $ \ A \ \ 8 uF C \ ` DWI O S \ \ 1f1 N // u•.Wi wa # a d r S \ \\\\\ ■ '' w y. a av•• o e Wo \ L uto I u0O CO \ Go K N C /' E F fi W \\ 0 W Z OCJ / c9 ON Z Z \�\ a 11 ` �- a0 W W M.- o � G F ..+ O 7 TJ n •- - 1I( Z N O. U N v1 T `- 1 N 'O e.i UO 4i i J O Z O Z Z - m o wa$.. yy W er n •� - Po 00b uY �O D O N O d M. y y If'4d al 6 u61 u u3i O E.,0 ITO 6 = Y e0 u u vi m VJon .' r i i_ the bedrock and the geometry of the cut should be considered. c oco T o Based on Lines 1 and 3 and possibly 7 there appear to T I F--4 be hard knobs or I. layers within the rock mass. These may J I � be metamorphic facies changes or simply less fractured, J N W r, i 0 f less weatherer, or recemented areas. These may show Y W 7 0 ^ W w Z W N W velocities in excess of 7000 ft/sec and may call for v,J � N W ` N w Q Z localized blasting depending on their geometry and size � � � w ` :: .•• w t� 4 with respect to the total cut. i o I =' ; y aO On Line 4 there is an obvious resistant rock unit I 1� - which shows velccities of at least. 7500 it/sec. Although 0 3 these types of features may be fractured and allow for �� 4 0 N �. i c N Ln N W f_ considerable ripping, they may also require general i ,moo »� 4 133j-H1ei3�J »-Nld3a IZ f blasting depending on the nature of the cut. 1..__- 1d3� Nj I_ Much of the rock at this site has thin metamorphic W LA f LA foliations and may be more ripp.ble than expected based 0 z I f o purely on seismic velocities. This could also, but would � - a not necessarily, be the case with the dense rock such as �'' I_ `� M I I l i'I c3 observed on Line 4. A test rippability program on the _ I 9 segments discovered b the seismic programs or by N I i _ hardestBm Y inspection would be useful is determining a:teal 'i rn? II I W �_ ' 133d-H1d34 N J i I -7 j rJ I I Z N J I I V - �' rippability at this site. To some extent this has been -� I I I done is the cuts investigated by Lines S and 7. Z �, o ? I y i ZU9 '0° o O z iT �.J.o C/) o ,n � Ln o s N ' - N 1f) I ' I :V LPh I .03J-u1d_0 . L3_'-uld3n L'3�-�1d34 NYUND ASSOCIATES.INC. f l NYUNO ASSOCIATE&INC. NYUNO ASSOCIATES,INC. •J� AYUNO ASSOCIATES, INC. "g ee-:a_r:a":;a: :a ''• f O8O8CIENCE CONSULTANTS "9' e••q 7. _ INTRODUCTION ISeven seismic refraction lines were conducted in an f area of proposed excavation in a proposed development site Project N88-150-02 east of Elsinore, California. The subject area is October 24, 1988 I underlain by metamorphic rocks of the Bedford Canyon fm. �- Stoney-Miller Consultants The purpose of this investigation was to determine the Attn: Mr. Gary Stoney RIPPABILITY INVESTIGATION seismic velocities in areas of proposed cut and determine 14 Hughes, Ste B-101 Irvine, CA 92718 Proposed ExcavationSites ease of excavation (ri _ Elsinorere,, CaliforniaCo � ppability). Dear Yr. Stoney: A total of 1380 feet of retraction line was surveyed. Attached is a copy of the report on the Elsinore Field work was conducted on October 18, 1988. The sites. Sorry for the delay-it seems something is always locations of the lines are shown on the site plan prepared �- coming up. The results are sbout as noted in the field with by Stoney-Miller Consultants. Elevation control was not highest velocities o* Line 4. The cuts seem to easily be ripping up to 6200 ft/rec and possibly up to 7000. available and was estimated in the field. RYLAND ASSOCIATES, INC. Please contact me if you have any questions. I also Project Number 88-150-02 f include an invoice. METHODOLOGY October 24, 1988 The seismic refraction method makes use of the time [- Bests a s, ( required for a seismic (acoustic) wave to travel various distances to calculate the subsurface configuration of the p6hen Ryland surveyed area. In this series of surveys ground-motion sensitive Prepared for transducers (geophones) were placed at 15-20 foot (- Stoney-Miller Consultants t Irvine, California -[ intervals along the survey lines. The lengths of Lines C 2-5 and 7 were each 180 and Lines 1 and 6 240 feet. Seismic energy was initiated into the lines by means l� of repeated sledge hammer impacts. The small ground - motion generated is converted into an electric current by Lthe geophones and then amplified and displayed by the ' �_ INLAND ASSOCIATES,INC. INLAND ASSOCIATES,INC, • C I � (SC1N07�3S i -1 iW ) WW1 I �- (S(1N1�J�SII-liW ) NWT 1 1 ;• � (SONOJ3SI-11IW ) 3WI1 1 I_l1.L I.L_I_I.I_IJ_LL1L1 I_I I.I I L I.l LL I I_IJ 1.I I.I_l_t t. I , ��J_LJ_.I_J__I_L —t_I_�_L.1..1._L_L 1._1..J.. L_L I. I._L. I. I. J m N LIIII � II � I � � � � IL (� n i IS) � s e � /� _ C\I n ° e 1 l V ° ° • uJ IE " w w " ' m _ n m w Z .. 0 Z rJ e H° ° ° • Z H Q r - ILlV— I_ I ill O 0 U\ J.j I e/ i Lo n " LLI w _ " e e we l"I'TTTT-r-r T-"TT r (n ell (�1 LD C�� @ @ LD @ I�J CJ CJ @ C9 c`� @ —r- l 1 1 ! I (hl UT1. T. -1 IT14 :1WT1 - NYLAND ASSOCIATES•INC. NYLAND ASSOCIATES.INC (�ON0D3S [-1"1 I W ) 3W I 1 AYIAND ASSOCIATES,IMC a , k, • ' seismograph. For this investigation a Geometrics ES121O In general this site is characterized by at least seismograph was used. This device has the ability to three subsurface layers with lateral variations in a - parallel to foliation is commonly faster. Where I "build-up" or stack the small signals generated by several complex configuration affected by erosion and weathering. -observable the line orientation is noted.� j of these small im Extreme topographic relief of the surface or a Yrcts into a larger-amplitude, readable Several of the lines were underlain by foliated l signal. The arrival times of the seismic wave at each refractor can introduce errors in depth and velocity metamorphic rocks which appeared relatively friable at the I .' geophone and the time of impact are recorded by the surface. Some lines such an 4, 5, and 7 appeared to be calculations. seismograph and presented visually and on paper records. underlain by more massive, dense material. When conducting surveys directly on a bedrock surface i Impacts were made at each end, at the centers, and Surficial velocities is relatively weathered looser the generation and detection of a head wave (first arrival when possible at points beyond the ends of the lines. and broken materials are less than 4000 it/sec. Denser ` compressional wave) may sometimes be difficult and the These multiple shot points yield optimal data for the first arrival noted may be a later waveform. material including some weathered or softer bedrock ( seismic interpretation. ! There will often be an increase in excavation exhibits velocities of 4000-6000 ft/sec. Harder bedrock , By plotting the delay time of arrivals versus has velocities in excess of 8000 it/sec with some observed difficulty as a seismic interface is approached and the - ; distance ind by various algebraic manipulations the depth up to 7500 it/sec. l calculated interface may represent the average depth of and configuration may be measured. The general reciprocal i transition rather than the top. . " i method was used primarily in interpretation; in complex Sources of Error Line Descriptions fareas this was supplemented by end point approximation and Unusual phenomena such as intermediate velocity thin Inspection. The data reduction was computer-assisted layers (blind zones) or lower velocity layers beneath F The seismic lines were located near areas of mayor �- using the program GRBYIX. higher velocity layers (hidden zones) may cause proposed cuts and were selected by Stoney-Miller _ t f interpretive error. Consultants. Interpretive seismic sections and !_ OBSERVATIONS AND GEOLOGIC INTERPRETATIONS Seismic waves do not travel only vertically. The time-distance plots are attached. The seismic retraction method produces a series of depths given could also, in some instances, be lateral Line 1 was surveyed north-south parallel to foliation data from which an interpretation is made. The distances to a higher velocity material. That is, f on a ridge-top. This line shows several lateral changes. cross-section depths may not always be vertical. � Much of the line is underlain by relatively weathered Interpretation is generally not unique and lacking other _ �I Some rocks may have animotropic behavior; that is bedrock with velocities of 3550-4150 ft/sec with a control data such as well logs may differ from actuality r _ higher velocity in some directions than in others; those .� low-velocity material near station 80. Along most of the in some instances. In this interpretation emphasis was I velocities measured may not always be fastest. This is line this material is further underlain at depths of 10-20 placed on the location of any possible areas of high 1 seismic velocity. expected in foliated metamorphic rocks where the direction feet by harder bedrock witb velocities of 4590-4930 l_ r ft/sec. However, near station 50 is a near-surface bard knob with velocities around 6670 ft/sec. RYLAND ASSOCIATE&INC, A/LAND ASSOCIATE&INC. l ( NYLAND ASSOCIATE&INC. Y.