A Rock Slope Stability Analysis at West-Northwest (WNW) Part Of

International Journal of Scientific & Engineering Research Volume 9, Issue 5, May-2018 999 ISSN 2229-5518

A Rock Slope Stability Analysis at West- Northwest (WNW) part of Barangay Cayumbay, Tanay, Rizal along the selected 5 stations of the 1.8km section of MARILAQUE Highway using inputs from Structural, Geomorphologic and Rock Mass Classification System

Vhon M. Barquilla, Ma. Patricia Bernadette A. Soliman

Abstract— Marikina-Infanta Highway or MARILAQUE highway which stands for Marikina-Rizal-Laguna-Quezon, is a highway that starts in Marikina and goes all the way to the Sierra Madre Mountain Ranges of Rizal, Laguna, and, finally, to Infanta, Quezon. The overall resolution of this research is to conduct an engineering geological study on the area in Tanay, Rizal along MARILAQUE highway. The area traverses parts of Barangay Cayumbay where rockfalls are a major problem. The geological study includes reconnaissance survey in the area, rock mass classification using Bieniawski’s RMR and Barton’s Q-System, and recommendation of any engineering mitigating measure to lessen any geologic hazard imposed by rock failure. Given a very low value for Q, it means that the study area is prone to failure; thus, it can be concluded that the 1.8km WNW part of Tanay, Rizal along the MARILAQUE highway is very prone to impending geologic hazard of rockfall. The study area also comprises splay of faults from the Philippines Fault Zone, different kinds of igneous rocks, which came from the Laguna Caldera of the Laguna de Bay, and sedimentary rocks, which indicate that some parts of Rizal were once submerged in the waters.

Keywords— MARILAQUE Highway, Bieniawski’s RMR, Barton’s Q-System

Index Terms— MARILAQUE = Marikina-Rizal-Laguna-Quezon, Q = Barton’s Q-System, RMR = Rock Mass Rating, WNW = West Northwest ——————————  —————————— 1 INTRODUCTION IJSER HE province of Rizal belongs to Region IV-A or more cal survey with regards to structural and geomorphology of T commonly known as the CALABARZON Region in the the area under study; (2) to implement Rock Mass Classifica- island of Luzon. It is one of the country’s first-class prov- tion (RMR) in the study area; (3) to perform a rock slope engi- inces that enjoys a natural beauty of nature and a perfect set- neering studies to identify any impending geologic hazard of ting for investments, business establishments and human set- rockfall along a section of MARILAQUE highway, which is tlements. The area is bounded by the mountain ranges of Sier- about 1.8km, and; (4) to generate the slope stability analysis ra Madre and Quezon Province in the east, the province of and assessment of the area using Barton’s Q-System. Laguna in the southwest, the province of Bulacan in the north, Metropolitan Manila in the WNW portion and by Laguna de 1.3 Scope Bay in SSW portion. Rizal is one of the neighboring provinces The purpose of this study is to identify discontinuities i.e. of Metro Manila. wedges of joints, beddings, fractures, and faults, that will in- duce rock slope failure or rockfall in the area along the 1.1 Background and problem motivation MARILAQUE Highway that traverses the WNW part of Ba- For this study, the chosen location is the MARILAQUE high- rangay Cayumbay, Tanay, Rizal. This study is only applicable way that traverses the WNW part of Barangay Cayumbay, on the said area because different areas have different soil and Tanay, Rizal. rock profile, composition, failure mechanism, weathering, etc. This particular study would like to address the query: How This research project will be based on the rock mass character- susceptible is the West-Northwest (WNW) part of Barangay ization by using Barton’s Q-system as input to the design of Cayumbay, Tanay, Rizal along 1.8km section of MARILAQUE any mitigating measure for rock slope failures. There is also Highway to slope instability particularly to any impending geologic limited published works on the chosen study area. hazard such as rockfall or planar rockslides along discontinuities?

2 REVIEW OF RELATED WORK 1.2 Overall aim The major objectives of this study are: (1) to conduct geologi- Studies conducted in the rock units of the Southern Sierra Ma-

IJSER © 2018 http://www.ijser.org International Journal of Scientific & Engineering Research Volume 9, Issue 5, May-2018 1000 ISSN 2229-5518 dre Mountains contributed to the understanding of the under- stratigraphy of SSM, the age of the ophiolitic basement rocks lying stratigraphy, tectonics and petrology as well as the in- and the correlation of number of stratigraphic units remain terpretations of the geomorphology, rock mechanics, and geo- unresolved. As with the NSM, the SSM was a site where Eo- logic history of the area. Oligocene arc magmatism took place and this was marked by quartz diorite-granodiorite. 2.1 Geological Considerations The work of Peña [6] defined that on a regional scale, Tanay Tanay is part of the province of Rizal and is situated along the is said to be included in the stratigraphic columns of Northern eastern part of the island of Luzon. It is underlain by a north- Sierra Madre-Caraballo and Southern Sierra Madre. south to north-northeast strips of Paleocene rock units along Tanay, Rizal which is the location for this study is affected the length of the Sierra Madre Mountain Ranges. The munici- by four major earthquake generators which includes the pality of Tanay has a complete sequence of Paleogene sedi- Marikina Valley Fault System, the Infanta Segment of the Phil- mentary rocks which represents the Paleocene-Eocene- ippine Fault, and two unnamed faults which are 4.0 km and Oligocene sedimentation that is unique in the Philippine ar- 5.96 km from the study area. chipelago. Commonly, ophiolites or ophiolitic complexes Barrier [7], that the Infanta segment of the sinistral Philip- comprise the basement of East Luzon. pine Fault, which is approximately 54.0 km from the study The Kinabuan Formation was named by Melendres and area was relatively seismically quiet and was related with an- Versoza (1960) for the flysch-like sedimentary deposits along other seismic gap. This seismic gap is believed to indicate that Kinabuan Creek which is north of Santa Ines, Antipolo, Rizal stress is accumulating and is not being released which makes [1]. The basal part of the sedimentary sequence was said to be it a candidate site for major earthquake. associated with underlying pillow basalts and basaltic The researchers also believed that the province of Tanay is breccias. The basalts represented the volcanic carapace of the affected by the Marikina Valley Fault System (MVFS) that ophiolite, whereas the pelagic sedimentary sequence consti- transects parts of eastern Metro Manila and possibly extend tuted the sedimentary cover of the Montalban Ophiolitic southwards to Tagaytay Ridge. It also belongs to a system of Complex. faults and subduction zones that accommodates an oblique As described by Cruz [2], the general area of Tanay, Rizal convergence between the Philippine Sea Plate and Eurasian was underlain by intensely disturbed suite of sedimentary Plate. rocks presumed to be of Cretaceous age which are Rimando [8] discovered that the neotectonic features along unconformably overlain by Eocene sediments, non-cherty the MVFS indicated a dominantly dextral strike-slip motion limestone, and cherty limestone. Another unconformity during its most recent activity which was believed to be Late caused the generation for the deposition of Miocene sedimen- Pleistocene to Holocene in age. Also, the variations in the rati- tary sequences composed of agglomerate and massive volcan- os of vertical to horizontal displacements for the segments ic rocks. Quaternary alluvium represented the younger rock implied a dominantly dextral motion of the West Marikina unit found along riverbanks as fluviatile deposit. Valley fault (WMVF) and oblique dextral motion for the East The geomorphology of Sierra Madre was described by Marikina Valley fault (EMVF). Lateral advection of the block IJSERbounded by the MVFS and the Philippine fault zone (PFZ) Wernstedt [3] and indicated that Sierra Madre, which is very rugged and heavily forested, formed the eastern margin of the best explains the observed kinematics of the MVFS. This was Cagayan Valley. This mountain range was said to be com- the result of compression during the westward drift of the posed of essentially large uplifted and tilted block of land with Philippine Sea Plate and northern Luzon and occurs through an abrupt slope facing the Pacific Ocean and with a gentler slip along the WMVF and EMVF at rates of 5–7 mm/yr. descent to the Cagayan Valley. The resistant intrusive igneous Rodrigo [9] concluded that the slumps, olistoliths and core of the highlands was overlain by a mantle of Tertiary sed- olistostromes found on the western flanks of Southern Sierra imentary and basic extrusive igneous rocks. Madre are product of large earthquakes related on the colli- Encarnacion [4] stated that the ophiolitic rocks found in sion of the Palawan Microcontinental Block to that of the Phil- Southern Sierra Madre (SSM) was first reported by Karig ippine Mobile Belt during Middle Miocene. Hence, previously (1983). The Montalban ophiolite described the assemblage of Angat formation was considered in the Norzagaray quadran- contiguous Cretaceous pillow lavas, diabase dikes and gabbro gle to be incorporated as a lower member of the conformably found in the Southern Sierra Madre of Luzon which is situated overlying Middle Miocene Madlum Formation. He also said east of the East Marikina Valley Fault. These rocks along with that the deformation found in the area were manifested at the a sheeted dike and gabbro sequence just west–northwest (be- base of the former Angat Formation. tween the West and East Marikina Valley Faults) as well as 2.2 Geotechnical Considerations isolated pillow lavas to the east were all grouped together as In terms of the application of geotechnical engineering in the the Angat ophiolite by Karig (1983). area, several articles written by renowned Geotechnical Engi- Furthermore, Queaño [5] said that the southern Sierra Ma- neers were considered. dre is a N-S trending mountain range extending over 200 km The Rock Quality Designation index (RQD) was developed on the eastern side of Luzon. It is separated from the Northern by Deere [10] to provide a quantitative estimate of rock mass Sierra Madre (NSM) by the active Philippine Fault. To the quality from drill core logs. Deere defined the RQD as the per- west, it is onlapped by the sediments of the Central Valley centage of the sum of intact core pieces longer than 100 mm Basin (Ringenbach, 1992). Despite the investigations about the divided by the total length of drill cores. The core should be at IJSER © 2018 http://www.ijser.org International Journal of Scientific & Engineering Research Volume 9, Issue 5, May-2018 1001 ISSN 2229-5518

least NW size (54.7 mm in diameter) and should be drilled The six parameters for the Q-system includes the Rock with a double-tube core barrel, (Hoek, 1995). Quality Designation which measures the degree of jointing, Jn Palmström [11] suggested that, when no core is available or joint set number, Jr or joint roughness number, Ja or joint but discontinuity traces are visible in surface exposures or alteration number, Jw or joint water reduction factor, and exploration adits, the RQD may be estimated from the number Stress Related Factor or SRF. of discontinuities per unit volume. The suggested relationship The number of joint sets, which was suggested as an addi- for clay-free rock masses was: tion to RQD by Cecil (1970) who was a Ph.D. student of Deere, (1) has remained an important part of Q, but is remarkably absent from Bieniawski’s RMR and is therefore also absent from the where Jv is the sum of the number of joints per unit length Geological Strength Index (GSI), which is used as basis for for all joint (discontinuity) sets known as the volumetric joint Hoek-Brown non-empirical failure condition [15]. count. In order to use the Barton’s Q-system, majority of the study focused mainly on hard, jointed rocks including weakness RQD was also considered as a directionally dependent pa- zones which is very common on the chosen study area located rameter; therefore, its value may change significantly, depend- at the WNW part of Barangay Cayumbay, Tanay, Rizal. It is ing upon the borehole orientation; however, those fractures, also important to take note that combining the application of which are identified to have been caused by handling or drill- the Q-system with deformation measurements and numerical ing process, shall be ignored when determining the value of simulations in squeezing rock or very weak rock is needed. RQD. Q-values can also be determined in different ways, which Furthermore, Bieniawski [12] published the details of a rock included geological mapping in underground excavations, on mass classification called the Geomechanics Classification or the surface, or alternatively by core logging. The most correct the Rock Mass Rating (RMR) system, (Hoek, 1995). For the values are obtained from geological mapping underground. past decades, this classification system has been successively But since the area under study is on the surface, geologic refined. The UCS or Uniaxial Compressive Strength of a rock, mapping would be performed there. RQD, the discontinuity spacing, condition, and orientation, For this study, the method of Barton or the Barton’s Q- and the conditions of groundwater were the parameters con- system would be used since the RMR system that he made is sidered to categorize a rock mass when using the Bieniawski’s more detailed and it will give the researchers an in-depth RMR. analysis of the rock masses in the chosen area of study. In order to use the RMR classification, the rock which con- Given the aforementioned reports, no studies were yet tains an intact rock with any accompanying discontinuities is conducted regarding the stability and strength of the rocks in divided into several regions followed by the determination of Southern Sierra Madre, particularly along the WNW part of the classification parameters for each said region from meas- Barangay Cayumbay, Tanay, Rizal. Therefore, this research urements obtained in the field. It should be noted that the rat- aims to conduct a detailed study to resolve the problem of ings, which are given for discontinuity spacing, apply to rock rock slope instability in Tanay through inputs from geomor- masses having three sets ofIJSER discontinuities. Thus, when only phological, structural geology and geological engineering two sets of discontinuities are present, a conservative assess- studies and assessment. ment is obtained. On the other hand, the Q-system was developed at the

Norwegian Geotechnical Institute (NGI) in 1974, and it origi- 3 METHODOLOGY nally included a little more than 200 tunnel case histories, To understand better what factors governing the slope insta- mainly from Scandinavia (Barton et al., 1974) [13]. bility of the study area, having an initial knowledge to the area Barton’s Q-system [14] may be used for classification of the is necessary. rock mass around an underground opening, as well as for field mapping. High Q-values indicates good stability and low (a) Desk Study and Data Acquisition values means poor stability. Based on the 6 parameters need- To acquire an initial knowledge of the study area, reviewing ed, the value for Q is obtained by using the equation: literatures, articles and journals related to the area are important. Review of previous work on Tanay, Rizal such as geo- (2) logical reports, geotechnical reports, theses, geologic maps and topographic maps were gathered to provide information

———————————————— about the geology of the area. Review of geotechnical reports • Vhon M. Barquilla is currently taking an undergraduate degree of Geologi- will help in identifying what methods and techniques are suit- cal Science and Engineering in Mapúa University, Philippines. E-mail: able to use in this study to gather information on the area, see [email protected] Fig. 1. • Ma. Patricia Bernadette A. Soliman is currently taking an undergraduate The 1.8km road of the study area on MARILAQUE high- degree of Geological Science and Engineering in Mapúa University, Phil- ippines. E-mail: [email protected] way was divided into 3 stations measuring 600 meters each, and at each station, 100 sets of strike, dip, and dip direction were taken to observe the variation in the discontinuities on

each section of the road.

The first station is located at 14°36.676' N and 121°17.892' E, IJSER © 2018 http://www.ijser.org International Journal of Scientific & Engineering Research Volume 9, Issue 5, May-2018 1002 ISSN 2229-5518 the second station is located at 14°36.747' N and 121°17.953' E, such as joints, faults, fractures, and bedding planes were rec- while the last station is located at 14°36.573' N and 121°18.171' orded and plotted in a map together with their orientations. E. These structural features controlled the type of failure that Another joint mapping, called RMR Logging, was conduct- may occur in the study area. Within the study area several ed to determine the Rock Mass Rating (RMR) of the rocks that stations were placed to record these structural features, in each will be used in the Q-system analysis of the study area. To station, 100 sets of strike, dip and dip direction were taken to have an in-depth analysis of the outcrops, the study area was observe the variation of these structural features. divided into five sections each measuring 360 meters apart. A total of 300 strike, dip, and dip direction data were col- The first station is located at 14°36.675' N and 121°17.897' E, lected last May 22, 2017. The 1.8km road of the study area on and is part of the Kinabuan Formation. The second station is MARILAQUE highway was divided into 3 stations measuring located at 14°36.75' N and 121°17.964' E, and is part of the 600 meters each, and at each station, 100 sets of strike, dip, and Kinabuan Formation. The third station is located at 14°36.727' dip direction was taken to observe the variation in the discon- N and 121°18.066' E, and is also part of the Kinabuan For- tinuities on each section of the road. mation. The fourth station is located at 14°36.664' N and The first station is located at 14°36.676' N and 121°17.892' E, 121°18.155' E, and is also part of the Kinabuan Formation. The the second station is located at 14°36.747' N and 121°17.953' E, last station is located at 14°36.571' N and 121°18.177' E, and is while the last station is located at 14°36.573' N and 121°18.171' also part of the Kinabuan Formation. E. Another joint mapping, called RMR Logging, was done last June 12, 2017 to determine the Rock Mass Rating (RMR) of the rocks in the study area. To have an in-depth analysis of the outcrops, the study area was divided into five sections each measuring 360 meters apart. To verify the joint mapping done last June 12 another joint mapping was done last August 15, 2017 to determine the Rock Mass Rating of the rocks in the study area. Likewise, the area was divided into five sections each measuring 360 meters apart. On October 25, 2017, the researchers brought the rock samples collected last October 20 and 23 to Mines and Geosciences Bureau for thin section and on November 7 the researchers did a petrographic analysis of the thin sections to verify the lithology of the study area. Based on the results of the thin section analyses, the researchers concluded that the rocks in the study area are part of IJSERthe Kinabuan Formation of the Southern Sierra Madre stratigraphic column.

(c) Geotechnical Investigation On the geotechnical investigation part, rock mass characteriza- tion using Barton’s Q-system was used to understand the strength of the rocks and to determine how slopes in the area Fig. 1. Topographic Map of the study area. are more likely to fail. There are six (6) parameters such as, (b) Rock Quality Designation (RQD), joint set number, joint Field Investigation roughness number, joint alteration number, joint water reduc- The geological investigation is divided into two, the lithologic tion factor, and Stress Related Factor (SRF) used to determine mapping and structural mapping. the rock strength of the study area. The lithologic mapping concentrated on the geologic char- These properties of the rock slope were recorded following acterization and was done by field mapping. This dealt with the guidelines used by Grimstad and Barton and these guide- the type of lithology, vegetation condition and the geomor- lines were used in each designated station within the study phology found in the study area. These includes the identifica- area to observe its susceptibility to slope failure. Rock mass tion of the stratigraphic section, material present within the stability were influenced by the several parameters for Q- study area and its characteristics. A number of rock samples system but these three factors are most important (Degree of were taken in the different parts of the study area and were jointing, Joint Frictions and Stress). The degree of jointing or analyzed. Through these rock samples the lithology, type of block size was determined by the joint pattern such as joint material present and it`s characteristics helped in determining orientation and joint spacing. The vertical stress in a rock mass how these materials are susceptible to failure. commonly depends on the depth below the surface. However, Structural mapping, on the other hand dealt with the struc- tectonic stresses and anisotropic stresses due to topography tural features present on the study area and these were ana- can be more influential in some areas. Stability of the under- lyzed to understand its effect on the slope. Structural features IJSER © 2018 http://www.ijser.org International Journal of Scientific & Engineering Research Volume 9, Issue 5, May-2018 1003 ISSN 2229-5518 ground excavation will generally depend on the stress magni- the stereographic projection of station 1 a rose diagram can be tude in relation to the rock strength. created. From the rose diagram, the major trends of the dis- To further understand the slope stability in the study area, continuities, which are SW and SE, created wedges that may the use of computer applications was needed. The collected slide directly towards the road. These trends can produce strike and dip were plotted on a stereonet to produce stereo- slope failure in the area called wedge failure. graphic projections and rose diagram through the use of Fine With the aid of the application called Fine software (Rock software: Rock Stability Program and STEREONET by Richard Stability Program), the data collected from the field was used Allmendinger. While in digitizing and analyzing maps and to produce a stereographic projection on the area which then aerial photographs ArcMap 10, QGIS v.16, Global Mapper and provided the factor of safety for the first station. The comput- Google Earth Pro were used. ed factor of safety (FS) of 1.28 is less than 1.50, and 1.50 is the On October 20 and 23, 2017 the researchers returned to the minimum value of FS for slope and rock stability, thus the study area to conduct Barton’s Q-system analysis. They also area is susceptible to rock failure. added another 140 data of strike, dip and dip direction on sta- At the second station, Fig. 3, there are two major trends of tions 3 (14°36.757' N and 121°18.018' E) and 4 (14°36.668' N discontinuities that are directed towards the NE and NW, and and 121°18.155' E) to further observe and analyze the variation these trends resembles a wedge. The orientation of the discon- in the discontinuities on each section of the road. tinuity trends is not directed towards the road but still is un- The researchers projected the data and/or joint sets taken stable based on the computation of factor of safety of the area in each station into a stereonet. The stereographic projection since it has a factor of safety of 1.01. will help to understand the trend of the joints and to determine what type of rock slope failure governs the area. Identi- fying the type of failure will help in determining the appropri- ate mitigating measure applicable on the area. On the first station, as seen from Fig. 2, the outcrop is composed of severely weathered basalt. Upon exposure of the outcrop to the atmosphere after road construction, the rocks un- dergone colloidal weathering. The joints and fracture planes on the outcrop were randomly oriented, and these discontinuities may be the result of the weathering and stress relaxation after the road was cut. IJSER

Fig. 3. Stereonet projection and rose diagram of the 100 strike and dip samples from Station 2 at 14°36.747' N and 121°17.953' E.

The third station, Fig. 4, shows two major trends of discontinuities that are directed towards the NW and SE, and these trends resembles a wedge. The orientation of the discontinuity trends may slide directly towards the road and the computed factor of safety of the area is 1.25.

Fig. 2. Stereonet projection and rose diagram of the 100 strike and dip samples from Station 1 at 14°36.676' N and 121°17.892' E.

The stereographic projection shows that the joints and fractures randomly intersects each other creating wedges. Using

There are 2 major trends of discontinuity at the fifth station, as seen from Fig. 6. The stereographic projection also implies wedging in the area. The trends are directed towards NE and SE as shown in its rose diagram. Relating the direction of the discontinuity trends to the road, it resembles wedges that is directed towards the road. Wedge failure may occur in this area because of the intersection of the major discontinuity trends and this is supported by the computation using the Rock Stability program which has a factor of safety of 1.07 which is less than 1.5.

Fig. 4. Stereonet projection and rose diagram of the 40 strike and dip samples from Station 3 at 14°36.757' N and 121°18.018' E

At the fourth station, Fig. 5, there are two major trends of discontinuities that are directed towards the NE and SW, and these trends resembles a wedge. The orientation of the discontinuity trends may also slide directly towards the road and the computed factor of safety of the area is quite satisfactory with a value of 1.60 which is greater than 1.50 (the minimum value of FS for slope and rock stability). Fig. 6. Stereonet projection and rose diagram of the 100 strike and dip samples from Station 5 at 14°36.573' N and 121°18.171' E.

IJSER

On October 26, 2017, the researchers brought the remaining rock samples collected last October 20 and 23 to the ILMO Testing Center for Compression Testing. Fig. 7 shows the methodological framework for this study.

Fig. 7. Methodological Flowchart. Fig. 5. Stereonet projection and rose diagram of the 100 strike and dip samples from Station 4 at 14°36.668' N and

121°18.155' E.

4 RESULTS/DISCUSSION As for station 1 which has an RMR of 28.73, it is classified as 4B (poor rock). As for station 2 which has an RMR of 40.49,

it is classified as 3B (fair rock). As for station 3 which has an Bieniawski’s Rock Mass Rating (RMR) RMR of 18.90, it is classified as 5A (very poor rock). As for

station 4 which has an RMR of 50.50, it is classified as 3A (fair TABLE 1 RESULTS OF BIENIAWSKI’S RMR rock). And as for station 5 which has an RMR of 69.08, it is classified as 2A (good rock).

The results for the RMR logging last June 12 coincides with the RMR logging last August 15 which states that for Station 1 the overall susceptibility rating for failing is Very High. As for

5 Station 2 the overall susceptibility rating for failing is Moder- 80 82 2B 4A 50.24 69.08 38.40 55.76 ate. As for Station 3 the overall susceptibility rating for failing 22846.11 22846.11 25900.13 is Very High. As for Station 4 the overall susceptibility rating for failing is Moderate. And for Station 5 the overall susceptibility rating for failing is Moderate. After the identification of the RMR Class by using Bieniawski’s RMR, the researchers then computed for the val- 4 60 5B 3A 8.18 29.99 35.71 50.50 ues of Q by using the corresponding values of the six parame- 12.8571 13980.32 16845.46 ters of Barton’s Q-system.

Barton’s Q-System The study area was divided into 5 stations and at each station the outcrop was divided into 3 meters to get the correspond- 3 0 5 50 5A 5A 4.50

18.90 15.31 ing values of the six parameters used in computing for the 2598.59 2887.32 value of Q. After obtaining the 6 parameters needed, the Q-value is cal- culated using equation of Barton’s Q-System. The six parameters for the Q-system includes the Rock Quality Designation which measures the degree of jointing, Jn or joint set number, 2 47 3B 3B Jr or joint roughness number, Ja or joint alteration number, Jw 83.65 40.49 40.08 50.75 48.86

22960.28 21908.62 or joint water reduction factor, and Stress Related Factor or SRF. As for station 1, data from the field is as follows:

IJSER SRF Q

1 RQD Jn Jr Ja Jw 47 4B 4B value 24.25 28.73 27.02 36.06 22.36

17004.20 10542.60 First 1-m 24.25 15 1 0.75 1 10 0.2156 Second 1-m 24.25 15 1 0.75 1 10 0.2156

Third 1-m 24.25 15 1 0.75 1 10 0.2156

Average Q for station 1 = 0.2156

ing SFRI (°) RFRI (°) RQD (%) SAMPLE NUMBER

IRS (MPa) SCOH (Pa) SCOH RMR Class RCOH (Pa) MRMR Ra RMR Rating MRMR Class As for station 2, data from the field is as follows:

SRF Q RQD Jn Jr Ja Jw Where: value IRS – Intact rock strength Third 1-m 83.65 9 1 0.75 1 10 1.2393 RQD – Rock quality designation Second 1-m 83.65 9 1 0.75 1 10 1.2393 RMR – Rock mass rating First 1-m 83.65 9 1 0.75 1 10 1.2393 MRMR – Modified rock mass rating RFRI – Reference unit friction RCOH – Reference unit cohesion Average Q for station 2 = 1.2393 SFRI – Slope unit friction SCOH – Slope unit cohesion

Based on the compression test of the rock samples, station 1, RQD Jn Jr Ja Jw SRF value station 2 and station 3 have compressive strength less than 10kN, First 1-m 0 9 1 4 1 5 which indicates that these stations are weak against compressive stress. While in station 4, station 5 and some parts of station 1 and The Q for station 3 = 0 station 3 their compressive strengths exceeds 20kN which indicates that they can withstand moderate to high stress. For this compressive test conducted at the ILMO Testing Center, stations As for station 4, data from the field is as follows: 1, 2 and 3 are more likely to fail than stations 4 and 5 because they cannot handle large amount of stress. SRF Q The rock masses on the area were also classified based on the RQD Jn Jr Ja Jw value computed Rock Mass Rating using Bieniawski`s RMR. Based on the computed RMR (stereographic projections), the first station is First 1-m 12.8571 15 3 3 1 5 0.1714 composed of poor rocks and from the computed factor of safety Second 1-m 12.8571 4 3 3 1 5 0.6429 the rock masses are highly susceptible to failure. The third sta- Third 1-m 12.8571 15 3 3 1 5 0.1714 tion is composed of very poor rocks which means that the rocks masses are very prone to failure. While the second and fifth sta- Average Q for station 4 = 0.3286 tions are composed of fair rocks, its factor of safety is less than 1.5 which means it is also susceptible to rock slope failure. The fourth station, on the other hand, even though it is made up of fair rocks As for station 5, data from the field is as follows: like the second and fifth stations, its factor of safety gives a satisfactory result of 1.6 which is greater than the minimum accepta- SRF Q ble factor of safety value of 1.5. RQD Jn Jr Ja Jw value The results of the stereographic projections as well as that of First 1-m 82 9 1 4 1 5 0.4556 Bieniawski’s RMR supports the results of Barton’s Q-System Second 1-m 82 9 1 4 1 5 0.4556 which gave a very low value for Q. The first station averaged a Q Third 1-m 82 15 1 4 1 5 0.2733 value of 0.2156 which is very poor in Q-system rating. The second station averaged a Q value of 1.2393 which is poor in Q-system Average Q for station 5 = 0.3948 rating. The third station averaged a Q value of 0 which is excep- tionally poor in Q-system rating. The fourth station averaged a Q value of 0.3286 which is very poor in Q-system rating. And the fifth station averaged a Q value of 0.3948 which is also very poor 5 CONCLUSIONS in Q-system rating. The two most widely used rock mass classification systems are Given a very low value for Q, it means that the study area is that of Bieniawski's RMR (1976, 1989) and Barton’s Q-system prone to failure; thus, it can be concluded that the selected 5 sec- IJSERtions of the 1.8km WNW part of Tanay, Rizal along the (1974). Both methods take into consideration the geological, geometric and design or engineering parameters in arriving at MARILAQUE highway is very prone to impending geologic a quantitative value of the rock mass quality. The similarities hazard of rockfall. between Bieniawski’s RMR and Barton’s Q-system came from the use of identical parameters in calculating the final rock mass quality rating. The differences between the systems lie in ACKNOWLEDGEMENT the different weightings given to similar parameters and in the use of distinct parameters in one or the other scheme. First and foremost, the researchers would like to thank their Bieniawski’s RMR and Barton’s Q-system deal with the ge- adviser, Doctor Petronilo E. Paña. Without his assistance and ology and geometry of the rock mass, and both schemes con- dedicated involvement in every step throughout the process, sider groundwater and some component of rock material this paper would have never been accomplished. strength. RMR uses compressive strength directly while the Q- The researchers also wish to express their sincere gratitude system only considers strength as it relates to in-situ stress in to Mapúa University for providing them with all the necessary competent rock. But the greatest difference between the two is facilities and equipment for the research. the lack of a stress parameter in Bieniawski’s RMR system. They are also grateful to all of their professors in the School For this study, the researchers have observed that the road of Civil, Environmental, and Geological Engineering. They are cut along MARILAQUE highway which exposed the rock extremely thankful and indebted to them for sharing their ex- masses to the atmosphere caused the rock masses to undergo pertise, and sincere and valuable guidance and encourage- stress relaxation due to the removal of overburden. Due to ment extended to them. these conditions, the rock masses produced fracturing and The researchers also want to extend their deep and sin- jointing in the area. Jointing can also be correlated to tectonism cerest appreciation and gratitude to Professor Jocelyn Vil- due to the presence of a splay of fault in the study area. These lanueva for sharing her expertise in the field of petrography discontinuities weaken the rock masses which greatly reduces that have been a big help for the them. the strength of the rock masses. The researchers would also like take this opportunity to ex-

IJSER © 2018 http://www.ijser.org International Journal of Scientific & Engineering Research Volume 9, Issue 5, May-2018 1007 ISSN 2229-5518 press their gratitude to their parents for their unceasing en- underground support, Fagernes”, Oslo: Norwegian Concrete Assn, pp. 46-66, 1993. couragement, support and attention. Lastly, the researchers would like to thank God for all the knowledge, enlightenment, guidance, and protection that He gave during this research.

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