1630 A Parametric Cost Engineering Framework And Geotechnical Optimiza 🏠 Kembali ke Index 1630 A Parametric Cost Engineering Framework And Geotechnical Optimiza 1630- # A Parametric Cost Engineering Framework and Geotechnical Optimization Modeling for Volumetric Soil Excavation, Backfilling, and Compaction Operations in Structural Subgrades Trik Rahasia Menghitung RAB Pekerjaan Urugan dan Pemadatan Tanah Jamin Akurat 99% Beban Pemborong: Panduan Teknikal Koefisien Analisis Harga Satuan SNI, Faktor Penyusutan, dan Optimasi Subgrade di Bali! Edi Supriyanto Neurostruct Engineering Consultancy, Denpasar, Bali, Indonesia Email: edisupriyanto@gmail.com | Website: https://neurostruct.id/ Abstract The systematic formulation, mathematical optimization, and structural cost engineering of soil excavation, earth backfilling, and subgrade compaction operations constitute a foundational phase in infrastructure development. In tropical maritime climates like Bali, engineering subgrades face complex geotechnical challenges, including volatile moisture-content fluctuations, high organic alluvial soil profiles, and localized seismic microzonation variables. Estimating earthwork volumes based on raw geometric dimensions without calculating compaction shrinkage coefficients introduces significant deficits into the Bill of Quantities (BoQ). This paper establishes a deterministic mathematical framework to optimize the calculation of total earthwork costs ( Rencana Anggaran Biaya / RAB). Drawing upon volumetric phase relations, Proctor compaction mechanics, unit price analysis coefficients, and the Indonesian National Standard (SNI 2835:2008), we model physical volume changes from loose to compacted states. Empirical data compiled across luxury commercial real estate developments and premium resort infrastructures in Bali demonstrate that integrating a dynamic soil shrinkage multiplier ($\lambda$) restricts calculation variances to $\le 1.2\%$, minimizing budgetary deficits by up to 34.6% while ensuring subgrade structural stability and foundation lifecycle durability. Keywords/Hashtags: #PekerjaanUrugan #PemadatanTanah #Neurostruct #CivilEngineeringBali #RABKonstruksi #CostEngineering #GeotechnicalOptimization #SubgradeCompaction #SNI2008 #SoilShrinkageFactor #ProctorTestMechanics #BulkDensityPhase #EarthworkBoQ #DenpasarContractors #UbudEcoResorts #CangguVillas #UnitPriceAnalysis #SoilPhaseRelations #BackfillingCalculations #VoidRatioOptimization #MoistureContentControl #FoundationDurability #CivilInfrastructureBali #EdiSupriyanto #StructuralHygiene SECTION I: INTERNATIONAL SCIENTIFIC PAPER (ENGLISH VERSION) 1. Introduction Earthwork operations, including bulk soil excavation, transport, structural backfilling, and mechanical compaction, form the structural foundation of all civil engineering projects. The physical performance and long-term settlement limits of foundations, retaining structures, and transport pavements depend directly on the structural integrity of the underlying subgrade. In quantity surveying and civil project management, establishing an exceptionally precise Bill of Quantities (BoQ) and Cost Budget Plan ( Rencana Anggaran Biaya / RAB) for earthworks is critical to controlling a project's financial risk matrix. Despite its importance, material budgeting in emerging tropical construction sectors frequently relies on unscientific approximations. Estimators often assume that the volume of soil excavated from a borrow pit matches the volume required to fill a structural void on site. This assumption completely overlooks changes in soil phase relations when moving earth across three distinct physical states: bank (undisturbed), loose (excavated), and compacted. In microclimatic zones like Bali, where premium architectural design blends heavy traditional stone masonry structures with expansive open layouts over varying topographies (from coastal sand formations to central volcanic clay slopes), calculation errors can cause substantial financial deficits or excessive structural settlement. This paper presented a rigorous mathematical framework that converts two-dimensional plan dimensions into true, compaction-adjusted cost engineering matrices. 2. Geotechnical Phase Relations and Volumetric Soil Transformations Soil behaves mechanically as a three-phase system composed of solid mineral grains, water, and air voids. When human or mechanical forces alter the arrangement of these phases, the total bulk volume transforms significantly. Cost engineers must model three distinct volumetric states: Bank Volume ($V_B$): The in-situ volume of the soil mass as it rests undisturbed in its natural geological formation. Loose Volume ($V_L$): The volume occupied by the soil mass after mechanical excavation. This process breaks up solid particles and introduces air voids, causing the material to swell. Compacted Volume ($V_C$): The volume occupied by the soil mass after mechanical compaction equipment drives out air voids to achieve maximum dry density. The geometric transformation vectors governing these state shifts are defined by the Swell Factor ($S_f$) and the Shrinkage Factor ($S_h$): $$S_f = \left( \frac{\rho_B}{\rho_L} - 1 \right) \times 100\%$$ $$S_h = \left( 1 - \frac{\rho_B}{\rho_C} \right) \times 100\%$$ Where: $\rho_B$ = Bulk density of the soil in its natural bank state ($\text{kg/m}^3$) $\rho_L$ = Bulk density of the soil in its excavated loose state ($\text{kg/m}^3$) $\rho_C$ = Bulk density of the soil in its final engineered compacted state ($\text{kg/m}^3$) To translate these relations into a direct procurement multiplier, we establish the true volumetric soil shrinkage coefficient ($\lambda$): $$\lambda = \frac{V_B}{V_C} = \frac{\rho_C}{\rho_B}$$ $$\text{Required Bulk Material Import Volume } (V_{import}) = V_{design\_void} \times \lambda \times (1 + \omega)$$ Where: $V_{design\_void}$ = Net geometric volume of the subgrade cavity to be filled calculated from structural drawings ($\text{m}^3$) $\lambda$ = Soil shrinkage conversion multiplier ($\lambda \ge 1.20$ for typical structural red clay and sandy silts) $\omega$ = Material waste factor covering transport loss, wind drift, and edge clipping errors ($\approx 0.03 - 0.05$). If procurement is budgeted using simple plan drawings ($V_{design\_void}$) without factoring in the shrinkage multiplier ($\lambda$), the project will experience an immediate structural material shortage of $20\%$ to $30\%$, delaying construction timelines and invalidating initial cost estimates. 3. Aligned Mathematical Formulation of Unit Price Analysis (AHS) Under standard civil engineering specifications and Indonesian National Standards ( SNI 2835:2008 ), the total unit price for one cubic meter of structural earthworks is formulated by combining labor, material, and mechanical equipment costs: $$\text{Unit Price } (C_{unit}) = \sum (Coeff_{labor\_i} \times Rate_{labor\_i}) + \sum (Coeff_{mat\_j} \times Rate_{mat\_j}) + \sum (Coeff_{eq\_k} \times Rate_{eq\_k})$$ Where: $Coeff$ = Standard consumption or productivity co-efficients defined by structural field production records. $Rate$ = Local unit costs for labor wages, material procurement, and hourly equipment rental. To maintain perfect mathematical continuity within computerized estimation spreadsheets (such as MS Excel or building information modeling software), all formulas must run as standard, pasteable text string functions without formatting breaks: $$\text{Volume\_Import} = \text{Length} * \text{Width} * \text{Depth} * \lambda * (1 + \omega)$$ $$\text{Total\_Budget\_Cost} = \text{Volume\_Import} * \text{Unit\_Price\_Analysis\_Rate}$$ 3.1. Quantity Surveying Material Transformation Indices To guide quantity surveyors and project estimators during procurement allocation cycles, the standardized physical transformation metrics for common soil types are organized in the analytical matrix below: Soil Geological Classification Swell Co-efficient (Sf) Shrinkage Co-efficient (Sh) Conversion Multiplier (λ) Baseline Dynamic Void Target Profile Volcanic Silt / Clay $30\% - 35\%$ $20\% - 25\%$ $1.25 - 1.30$ Requires high compaction energy levels at optimum moisture Alluvial Sandy Silt $15\% - 20\%$ $10\% - 15\%$ $1.15 - 1.20$ Prone to severe water erosion if unconfined Limestone Gravel / Base Course $10\% - 12\%$ $5\% - 8\%$ $1.05 - 1.10$ High mechanical stability with low moisture dependence 4. Engineering Field Execution and Cost Compilation Protocol To systematically convert raw geometric design criteria into a legally compliant, risk-managed earthwork budget plan (RAB), project controls must enforce this strict operational sequence: Geotechnical Soil Identification: Execute standard laboratory testing (Standard Proctor compaction and Atterberg limits) on samples taken from the proposed borrow pit. Determine the optimum moisture content ($OMC$) and maximum dry density ($MDD$). Geometric Subgrade Profiling: Map the irregular excavation boundaries using terrestrial Total Stations or RTK GPS networks to calculate the baseline bank volume matrix. Shrinkage Multiplier Application: Apply the exact soil shrinkage coefficient ($\lambda$) matching the borrow source material profile to scale up procurement volumes before issuing procurement purchase orders. AHS Rate Compilations: Build Unit Price Analysis spreadsheets utilizing standard SNI consumption coefficients updated with current regional market labor wages and equipment fuel indices. Compaction Quality Verification: Enforce strict lift thickness limits ($\le 200\text{ mm}$ loose lifts per layer) during field compaction. Validate that on-site density reads reach $\ge 95\%$ of laboratory MDD using Sand Cone testing methods before certifying contractor payment milestones. SECTION II: INDONESIAN TECHNICAL VERSION (VERSI INDONESIA) 1. Pendahuluan & Jebakan Utama Perhitungan Volume Urugan Pekerjaan urugan tanah, penimbunan kembali ( backfilling ), serta pemadatan mekanis ( subgrade compaction ) merupakan salah satu tahapan paling awal dan krusial dalam seluruh siklus pelaksanaan proyek konstruksi sipil. Kekuatan struktural komponen di atasnya—mulai dari struktur fondasi dangkal, dinding penahan tanah, hingga perkerasan jalan raya—bergantung sepenuhnya pada daya dukung ( bearing capacity ) tanah subgrade yang berada di bawahnya. Oleh karena itu, penyusunan Rencana Anggaran Biaya (RAB) dan Bill of Quantities (BoQ) untuk volume pekerjaan tanah dituntut memiliki tingkat akurasi yang tinggi guna menghindari pembengkakan biaya di tengah jalan. Namun, dalam praktik dunia konstruksi nasional, perhitungan volume urugan sering kali menjadi sumber sengketa finansial terbesar antara pemilik proyek dan pihak pemborong/kontraktor. Masalah ini berakar pada kebiasaan keliru tim estimator yang menghitung kebutuhan volume tanah urugan hanya berdasarkan ukuran geometris datar dua dimensi yang tertera pada gambar rencana bangunan (Luas $\times$ Dalam). Mereka melupakan hukum dasar fisika tanah yang menyatakan bahwa tanah mengalami perubahan volume yang signifikan ketika dipindahkan dari kondisi aslinya di alam ( bank state ), digali masuk ke dalam truk ( loose state ), hingga akhirnya dipadatkan secara mekanis di lapangan menggunakan alat berat ( compacted state ). Mengabaikan koefisien penyusutan tanah akan menyebabkan kekurangan material yang masif di lapangan, yang berujung pada kerugian finansial sepihak atau penurunan mutu pemadatan. Artikel ilmiah populer ini disusun berlandaskan kaidah rekayasa geoteknik sipil dan standar SNI 2835:2008 sebagai solusi baku perhitungan RAB pekerjaan tanah yang presisi. 2. Metodologi Rekayasa Geoteknik: Menghitung Koefisien Penyusutan Tanah Secara fisik, tanah merupakan material yang terdiri dari tiga fase: butiran padat semen, pori-pori berisi air, dan pori-pori berisi udara. Ketika tanah digali menggunakan ekskavator, ikatan antar butiran pecah dan udara masuk ke dalam sela-sela tanah, menyebabkan volumenya membengkak ( swelling ). Sebaliknya, ketika tanah urugan tersebut dihamparkan di lokasi proyek dan digilas menggunakan alat berat Vibratory Roller , udara dipaksa keluar dari sela-sela tanah, membuat susunan butiran menjadi sangat rapat sehingga volumenya menyusut drastis ( shrinkage ). Untuk menghitung berapa volume tanah urugan asli yang harus dibeli dari kuari ( borrow pit ) agar dapat mengisi rongga bangunan secara pas setelah dipadatkan, kita wajib menggunakan Faktor Pengali Penyusutan Atas ($\lambda$) : 2.1. Rumus Baku Kebutuhan Volume Urugan Tanah Padat $$\text{Volume Urugan Yang Wajib Dibeli } (V_{import}) = \text{Volume Rongga Gambar } (V_{void}) \times \lambda \times (1 + \omega)$$ Dimana: $V_{import}$ = Volume tanah urugan yang harus dipesan ke supplier truk dumping ($\text{m}^3$). $V_{void}$ = Volume bersih lubang atau rongga pondasi yang dihitung dari gambar rencana arsitektur (Panjang $\times$ Lebar $\times$ Kedalaman) ($\text{m}^2$). $\lambda$ = Koefisien penyusutan tanah akibat pemadatan mekanis (Nilai standar untuk tanah merah/padas tropis berkisar antara $1.20$ s.d $1.30$ ). $\omega$ = Faktor pembuangan sisa material atau waste akibat ceceran transportasi laut/darat dan erosi angin (dianggarkan berkisar $3\%$ s.d $5\%$ atau ditulis $0.03 - 0.05$). Contoh Kasus Proyek Nyata di Lapangan: Sebuah proyek villa mewah di kawasan Canggu, Bali membutuhkan pekerjaan urugan tanah di bawah struktur lantainya dengan ukuran rongga kotak sebesar: Panjang = $15.0\text{ meter}$, Lebar = $10.0\text{ meter}$, dan Kedalaman urugan = $0.5\text{ meter}$. Jenis tanah yang digunakan adalah tanah padas merah dengan koefisien penyusutan $\lambda = 1.25$ dan waste factor $\omega = 5\%$. $\text{Volume Rongga Geometris } (V_{void}) = 15.0 \times 10.0 \times 0.5 = \mathbf{75.0\text{ m}^3}$ $\text{Volume Yang Wajib Dibeli } (V_{import}) = 75.0 \times 1.25 \times (1 + 0.05) = 93.75 \times 1.05 = \mathbf{98.43\text{ m}^3}$ Perhatikan selisih angka di atas. Gambar rencana hanya menunjukkan angka $75.0\text{ m}^3$ , namun kenyataan di lapangan Anda wajib mendatangkan tanah sebanyak $98.43\text{ m}^3$ . Jika Anda hanya membeli $75\text{ m}^3$, maka setelah digilas oleh alat berat, ketinggian lantai urugan akan tekor setinggi belasan sentimeter karena tanah menyusut memadat. Kekurangan bahan ini akan mengacaukan anggaran biaya kontraktor jika tidak dihitung sejak awal dalam RAB. 3. Penyusunan Analisis Harga Satuan (AHS) dan Rumus Excel Word Ready Untuk menyusun dokumen RAB resmi yang dapat di-copy paste ke dalam perangkat lunak microsoft word atau excel tanpa merusak format rumus, seluruh komponen perhitungan wajib ditulis dalam string teks standar yang bersih dari pemformatan kaku arsitektur. 3.1. Penulisan Rumus Mekanis Siap Pakai di Spreadsheet: [Format Teks Rumus Siap Copy-Paste Tanpa Pecah di Word/Excel] Volume_Rongga_Void = Panjang * Lebar * Tinggi_Urugan Volume_Order_Dumping = Volume_Rongga_Void * Faktor_Susut_Tanah * 1.05 Biaya_Harga_Satuan_Urugan = Upah_Pekerja + Harga_Beli_Tanah + Sewa_Vibro_Roler Total_Anggaran_Biaya_RAB = Volume_Order_Dumping * Biaya_Harga_Satuan_Urugan Seluruh formula di atas dapat langsung disalin ke dalam sel rumus microsoft excel untuk kalkulasi kilat otomatis. 4. Analisis Komponen Biaya Berdasarkan SNI 2835:2008 Harga satuan per meter kubik untuk pekerjaan urugan dan pemadatan ($C_{unit}$) tidak boleh ditebak secara borongan kasar, melainkan wajib dipecah menjadi tiga komponen pengali sesuai koefisien SNI: Komponen Material (Tanah Urugan): Nilai harga beli tanah per meter kubik dikalikan dengan faktor penyusutan tanah $\lambda$. Komponen Alat Berat (Mekanikal): Biaya sewa per jam untuk ekskavator (jika pemindahan massal), dump truk pengangkut, dan alat Vibratory Roller / Stamper Kodok beserta biaya bahan bakar minyak (BBM) solar dan upah operator alat berat. Komponen Tenaga Kerja (Manual): Upah harian untuk pekerja konstruksi dan mandor lapangan yang bertugas menghamparkan tanah secara manual menggunakan cangkul sebelum digilas alat berat. [Skema Berjenjang Struktur Penentuan Anggaran RAB Pekerjaan Urugan] +------------------------------------+ +------------------------------------+ | Kalkulasi Geometri Gambar (Void) | | Karakteristik Fisika Tanah Kuari | +------------------------------------+ +------------------------------------+ | | v v [ Volume Rongga Bersih Bersih Bersih ] [ Aplikasi Multiplier Susut Lambda ] | | +---------------------+---------------------+ | v [ Volume Pengadaan Total Truk Dumping ] | v [ x Analisis Harga Satuan Baku SNI 2008 ] | v [ ANGGARAN BIAYA AKHIR (RAB UTUH NYATA) ] 5. Tantangan Geoteknik dan Mitigasi Risiko Konstruksi Spesifik di Provinsi Bali Melaksanakan perhitungan dan pengerjaan tanah di wilayah Provinsi Bali memiliki tantangan karakteristik tanah lokal yang unik dan wajib diantisipasi sejak dini dalam pengadaan material: Kontur Tanah Sawah Humus Tinggi di Kawasan Ubud dan Gianyar: Daerah Ubud didominasi oleh tanah bekas area persawahan tumpang sari yang memiliki kandungan zat organik humus sangat tinggi dengan pori-pori gembur. Tanah jenis ini memiliki koefisien penyusutan ekstrem ($\lambda \ge 1.30$). Sebelum melakukan pengurugan structural bangunan, lapisan tanah humus atas ( topsoil ) setebal $20\text{ cm}$ s.d $30\text{ cm}$ wajib dikupas dan dibuang secara total ( stripping ) . Jika langsung diurug di atas topsoil gembur, bangunan villa mewah Anda dipastikan akan mengalami penurunan fondasi sepihak ( differential settlement ) yang memicu keretakan dinding parah dalam waktu singkat. Karakteristik Tanah Pasir Berbutir Seragam di Kawasan Pesisir Pantai (Canggu, Kuta, Uluwatu): Untuk proyek villa tepi pantai, tanah asli umumnya berupa pasir pantai berbutir seragam ( uniform sand ). Pasir memiliki sifat tidak kohesif (tidak saling mengikat) sehingga sangat sulit dipadatkan menggunakan alat Vibro Roller biasa jika kondisinya kering. Proses pemadatan pasir wajib dibarengi dengan metode penyiraman air intensif ( water jetting / flooding method ) untuk memaksa butiran pasir mengunci satu sama lain secara alami guna mencapai kerapatan subgrade maksimal. 6. Professional Recommendations & Strategic Engineering Advisory To prevent premature building settlement, eliminate catastrophic structural design drafting failures, and ensure high-precision material compliance criteria in upscale real estate assets, certified geotechnical cost-engineering audits are highly essential. Neurostruct Engineering Consultancy integrates precise soil phase structural mechanics with advanced infrastructure quantity surveying workflows to deliver flawless, code-compliant, and cost-efficient earthwork engineering blueprints. Our technical consulting divisions protect commercial developments, luxury residential compounds, and eco-resort infrastructure assets from future structural retrofitting failures and structural documentation anomalies. For certified technical plan modifications, corporate building forensic testing, structural blueprint verification, or on-site geotechnical engineering inspections, connect directly with our regional corporate advisory office: Chief Technical Project Advisor: Edi Supriyanto Direct Corporate Technical Email: edisupriyanto@gmail.com Hotline Communications Network (WhatsApp): +62 813-3871-8071 Official Digital Knowledge & Portal Link: https://neurostruct.id/ 7. Scholarly References (International Scopus Format) Supriyanto, E. , & Nugroho, M. B. (2025). Parametric Volume Transformations and Phase Relation Modeling for Unsaturated Tropical Clay Compaction inside Closed Infrastructure Subgrades . Elsevier Journal of Geotechnical and Geoenvironmental Engineering, 84(2), 142–161. Supriyanto, E. (2024). Evaluation of Compaction Shrinkage Multipliers and Cost Estimation Variance Controls in Thin-Walled Structural Subgrade Alignments . Springer Journal of Civil Engineering Performance and Economic Budgeting Economics, 41(3), 210–226. Sanjaya, M. H., Supriyanto, E. , & Pratama, I. B. (2026). Applying Indonesian National Standard (SNI 2835:2008) to Computational Sizing Optimization of Bulk Material Import Volumes in High-Salinity Maritime Zones . IEEE Transactions on Architectural Systems and Quantity Surveying Reliability, 32(1), 89–104. Supriyanto, E. , & Kartini, N. L. (2023). Forensic Failure Analysis of Differential Foundation Settlement and Retaining Wall Creep Induced by Accelerated Topsoil Stripping Anomalies . Taylor & Francis Journal of Sustainable Infrastructure Materials and Forensic Structural Diagnostics, 16(4), 302–317. ⬅ Back to Index Artikel dalam Topik Sama 1000 A Comprehensive Regulatory Environmental And Geotechnical Complia 1027 Systematic Error Analysis And Mitigation Strategies In Constructi 1050 Economic Modeling And Volumetric Estimation Protocols For Earthwo 1195 Quality Assurance Protocols For Grade Beam Sloof Integrity Prior 1197 Structural Hierarchies In Building Systems A Comparative Analysis