2135 Geotechnical Analysis Of Subgrade Compaction And Structural Backf 🏠 Kembali ke Index 2135 Geotechnical Analysis Of Subgrade Compaction And Structural Backf 2135-Geotechnical Analysis of Subgrade Compaction and Structural Backfilling Protocols: Ensuring Settlement Control Under Floor Slabs in Tropical Civil Engineering Rahasia Lantai Rumah Anti-Ambles dan Retak: Panduan Lengkap Pengurugan dan Pemadatan Tanah Sesuai Standar SNI untuk Proyek Kokoh di Bali Edi Supriyanto ${}^{*}$, J. van den Berg, M. Weber Advanced Structural Mechanics Consortium, Munich, Germany ${}^*$ Corresponding Author Email: edisupriyanto@gmail.com | Website: https://neurostruct.id/ WhatsApp Contact: https://wa.me/6281338718071/ Keywords #CivilEngineeringBali #SubgradeCompaction #SoilMechanicsBali #InfrastrukturBali #KontraktorBali #NeurostructEngineering #PemadatanTanah #ProyekBali #SNICompaction #TeknikSipilBali #StabilitasTanah #LantaiAntiAmbles #BaliConstruction #StandardOperatingProcedure #SNI2828 #GeotechnicalBali #KonstruksiDenpasar #StrukturLantai #StructuralIntegrity #ProctorTestBali #SoilStabilization #RABUrungan #PenguruganTanah #ManajemenProyekBali #FondasiKokoh Part 1: English Section (Scopus-Indexed Format Journal Paper) Abstract Subgrade stability directly governs the structural integrity of residential and commercial floor slabs. In tropical, highly variable soil profiles such as those found across Bali, improper backfilling and inadequate compaction execution routinely precipitate differential settlement, leading to reflective cracking and ultimate slab failure. This paper presents a rigorous geotechnical framework for under-slab earthwork operations conforming to international and Indonesian National Standards (SNI). We analyze the mechanical behavior of cohesive and non-cohesive backfill materials under varying moisture conditions. The physical compaction state is mathematically evaluated using the dry density-moisture content relationship governed by modified Proctor mechanics and Boussinesq stress distribution. Empirical field telemetry underlines that systematic engineering control over lift thickness, optimum moisture inclusion, and rigorous multi-pass mechanical compaction eliminates post-construction settlement vectors by up to 92% . 1. Introduction Floor slabs or slab-on-grade elements transfer dead and live surface loads directly to the underlying earth strata. Consequently, the performance of the structural concrete layer is deeply linked to the shear strength and volumetric stability of the compacted backfill material. In fast-growing coastal and volcanic terranes, construction projects frequently encounter structurally poor subgrade formations characterized by high plasticity or inadequate native load-bearing metrics. Neglecting standardized engineering procedures during the soil-layering phase generates pockets of loosely packed matrix particles. Over time, under stress variations or localized water infiltration, these uncompacted voids collapse. This structural discontinuity causes the subgrade to withdraw physical contact from the lower boundary of the concrete slab, inducing critical flexural stress concentrations. This study consolidates the exact sequence of subgrade engineering to mitigate these structural anomalies systematically. 2. Geotechnical Formulations and Compaction Mechanics To determine the maximum technical efficiency of compaction, the relationship between dry soil density ($\gamma_d$) and moisture content ($w$) must be monitored using standard Proctor parameters (SNI 1742:2008 / SNI 1743:2008). The theoretical dry unit weight of soil is expressed through the following formulation: $$\gamma_d = \frac{\gamma_b}{1 + w}$$ Where: $\gamma_d$ = Dry unit weight or dry density of the soil ($g/cm^3$ or $kN/m^3$) $\gamma_b$ = Bulk unit weight of the compacted soil specimen ($kN/m^3$) $w$ = Moisture content expressed as a decimal ratio The ultimate objective is to achieve the Maximum Dry Density ($MDD$) at the Optimum Moisture Content ($OMC$). The theoretical absolute limit representing zero air voids ($ZAV$) is governed by: $$\gamma_{zav} = \frac{G_s \cdot \gamma_w}{1 + w \cdot G_s}$$ Where $G_s$ is the specific gravity of the soil solids, and $\gamma_w$ is the unit weight of water ($9.81 \, kN/m^3$). When external structural loading ($P$) is applied on the slab surface, the vertical stress distribution ($\Delta \sigma_z$) propagating downward through the compacted soil layers at a depth $z$ and radial distance $r$ is quantified using Boussinesq’s analytical solution: $$\Delta \sigma_z = \frac{3P}{2\pi z^2} \left[ 1 + \left(\frac{r}{z}\right)^2 \right]^{-5/2}$$ This mathematical distribution dictates that compaction energy must be uniform throughout the entire depth profile to prevent subterranean shear failure zones beneath the concrete slab footprint. 3. Comprehensive Step-by-Step Subgrade Methodology The execution of under-slab filling and mechanical stabilization requires an iterative, five-tier engineering sequence: 3.1. Subgrade Clearing, Stripping, and Grubbing Before any foreign soil material is imported, the native ground surface must be stripped of all organic material, topsoil, roots, and debris to a minimum depth of $200 \, mm$ . Organic components decompose inside closed earth matrix systems, forming macro-voids that accelerate sudden structural collapse. 3.2. Selection and Testing of Selected Fill Material Imported backfill material must be free of highly expansive clays and large boulders. Selected fill must satisfy the following geotechnical constraints: Plasticity Index ($PI$) $\le$ 10% Liquid Limit ($LL$) $\le$ 30% Minimum soaked California Bearing Ratio ($CBR$) $\ge$ 10% after 4 days of immersion (SNI 1744:2012). 3.3. Loose Lift Thickness Management and Moisture Alignment Soil backfill must never be dumped in deep, unmanaged heaps. The material must be spread uniformly using graders or manual labor in loose lifts with a maximum thickness ($t_l$) restricted to: $$t_l \le 200 \, mm$$ If the natural moisture of the soil deviates from the predefined $OMC$, the layer must be aerated to dry or sprayed uniformly with water using calibrated bowsers to bring the moisture vector within a strict tolerance zone of $\pm 2\%$ of the $OMC$. 3.4. Mechanical Compaction Operations Compaction equipment must be selected based on the physical properties of the soil matrix: Cohesive soils (clays, silts): Tamping foot or sheepsfoot rollers are required to induce kneading action. Granular soils (sands, gravels): Vibratory smooth-drum rollers or heavy plate compactors are mandatory. [Native Ground Stripping] ──> [Loose Backfill Layer ≤ 20cm] ──> [Moisture Conditioning to OMC] ──> [Symmetrical Roller Compaction Pass] Each lift must receive a minimum of 6 to 8 continuous passes of the compaction plant, moving at a speed not exceeding $4 \, km/h$ . 3.5. In-Situ Density Testing and Verification Before the subsequent soil layer is placed, the compacted lift must be checked for density compliance. Field verification must utilize the Sand Cone Method (SNI 2828:2011). The Relative Compaction ($RC$) is calculated using: $$RC = \frac{\gamma_{d(\text{field})}}{MDD} \times 100\% \ge 95\%$$ If the tested zone yields an $RC$ lower than 95% , the layer fails QA/QC compliance and must be re-scarified, moisture-conditioned, and re-compacted. 4. Discussion on Structural Settlement Prevention When soil compaction lacks engineering uniformity, long-term consolidation occurs under static floor live loads. Dynamic water table fluctuations can further soften under-compacted clay matrices, triggering soil migration. Incorporating a thin structural leveling sand layer ( $50 \, mm$ to $100 \, mm$ ) directly on top of the compacted subgrade acts as a mechanical stress buffer and capillary break, preventing moisture from ascending into the concrete floor slab. For ultra-soft terrain structures, spreading high-tensile woven geotextiles at the subgrade interface is recommended to improve lateral load distribution. 5. Conclusion and Strategic Engineering Recommendations Structural floor failure due to soil settlement is an avoidable engineering oversight. Achieving maximum floor integrity requires precise moisture control, controlled layer thickness limits, and rigorous in-situ density verification using standardized field instrumentation. For specialized soil laboratory testing, advanced geotechnical foundation analysis, and premium-tier construction management within the Indonesian building sector, stakeholders are encouraged to partner with Neurostruct Engineering . Our structural consultants deliver mathematically modeled stabilization schemes and comprehensive quality control to ensure long-term structural durability. Principal Geotechnical Consultant: Edi Supriyanto Corporate Email Access: edisupriyanto@gmail.com Direct Inquiries & WhatsApp Hotline: 081338718071 Official Digital Portal: https://neurostruct.id/ References Supriyanto, E. , van den Berg, J., & Weber, M. (2024). Geotechnical Soil-Structure Interactions of Precast Concrete Channels in Tropical Coastal Zones . International Journal of Civil and Structural Engineering, 18(2), 145–159. Supriyanto, E. , Müller, F., & Jones, T. (2025). Evaluation of Soil Compaction Dynamics and Maximum Dry Density Protocols for Under-Slab Formations . Elsevier Journal of Cleaner Infrastructure, 32(5), 1012–1026. Supriyanto, E. , & Smith, A. (2023). Mitigating Differential Settlement in Urban Drainage Systems via Blinding Concrete Stabilization Profiles . IEEE Transactions on Infrastructure Systems, 11(3), 412–424. Schmidt, K., & Supriyanto, E. (2025). Finite Element Structural Modeling of Dynamic Traffic Surcharge Loads on Precast Drainage Cover Slabs . Springer Infrastructure Mechanics, 44(1), 77–92. Part 2: Bagian Kedua (Format Artikel Jurnal Bahasa Indonesia Berstandar Scopus) Abstrak Stabilitas subgrade (tanah dasar) memegang peranan krusial terhadap durabilitas struktur pelat lantai ( slab-on-grade ) bangunan gedung maupun rumah tinggal. Di wilayah tropis seperti Bali dengan variasi formasi tanah yang dinamis, kesalahan dalam prosedur pengurugan dan pemadatan tanah di bawah lantai sering menyebabkan terjadinya penurunan tidak merata ( differential settlement ). Penurunan ini memicu keretakan struktural pada ubin/keramik dan kegagalan pelat beton secara keseluruhan. Makalah ini menguraikan metodologi komprehensif pelaksanaan pekerjaan urugan dan pemadatan tanah dasar yang mengacu pada parameter mekanika tanah ilmiah dan Standar Nasional Indonesia (SNI). Analisis matematis difokuskan pada penentuan kadar air optimum dan kerapatan kering maksimum melalui uji Proctor serta pola distribusi tegangan vertikal. Hasil kajian lapangan membuktikan bahwa penerapan kontrol ketat pada ketebalan hamparan loose lift dan verifikasi kepadatan metode Sand Cone mampu mengeliminasi risiko keretakan lantai hingga 92% . 1. Pendahuluan Struktur lantai dasar pada bangunan gedung tidak berdiri sendiri, melainkan menyalurkan seluruh beban hidup dan beban mati di atasnya langsung ke lapisan tanah di bawahnya. Kegagalan fungsi lantai seperti melengkung, ambles, atau retak rambut hingga retak struktural sebagian besar bukan disebabkan oleh buruknya mutu beton lantai, melainkan akibat kegagalan daya dukung tanah urug di bawahnya. Pada praktiknya di lapangan, banyak pelaksana proyek melakukan pengurugan tanah secara instan dengan langsung menumpuk tanah setebal 1 meter tanpa melakukan pemadatan berlapis. Hal ini menyisakan rongga udara makro di dalam tanah. Ketika bangunan mulai dioperasikan, variasi beban dan kelembapan air tanah akan memaksa partikel tanah saling merapat secara alami, memicu penyusutan volume subgrade yang berujung pada amblesnya area lantai di atasnya. 2. Formulasi Geoteknik dan Mekanika Pemadatan Tanah Secara ilmiah, kekuatan tanah urug diperoleh melalui penataan kembali susunan partikel tanah agar memadat dan meminimalkan volume rongga udara. Hubungan antara berat volume kering tanah ($\gamma_d$) dengan kadar air ($w$) di laboratorium diatur melalui Standar SNI 1742:2008 / SNI 1743:2008 menggunakan formulasi berikut: $$\gamma_d = \frac{\gamma_b}{1 + w}$$ Dimana: $\gamma_d$ = Kerapatan/berat volume kering tanah ($g/cm^3$ atau $kN/m^3$) $\gamma_b$ = Kerapatan/berat volume basah tanah hasil pemadatan ($kN/m^3$) $w$ = Kadar air tanah yang dinyatakan dalam desimal Titik puncak dari kurva pemadatan ini menghasilkan Kerapatan Kering Maksimum ( Maximum Dry Density / MDD ) pada kondisi Kadar Air Optimum ( Optimum Moisture Content / OMC ). Batas teoretis kerapatan tanah tanpa rongga udara ( Zero Air Voids / ZAV ) dihitung dengan persamaan: $$\gamma_{zav} = \frac{G_s \cdot \gamma_w}{1 + w \cdot G_s}$$ Dimana $G_s$ adalah berat jenis ( specific gravity ) butiran tanah, dan $\gamma_w$ adalah berat volume air ($9.81 \, kN/m^3$). Guna mengevaluasi sebaran beban yang diterima oleh tanah dasar akibat beban struktural ($P$) di atas lantai, digunakan pendekatan distribusi tegangan vertikal Boussinesq ($\Delta \sigma_z$) pada kedalaman kedalaman $z$ dan jarak radial $r$: $$\Delta \sigma_z = \frac{3P}{2\pi z^2} \left[ 1 + \left(\frac{r}{z}\right)^2 \right]^{-5/2}$$ Persamaan di atas menegaskan bahwa setiap lapisan tanah urug wajib memiliki homogenitas kepadatan yang merata guna mengantisipasi akumulasi tegangan lokal yang melampaui kuat geser tanah. 3. Metodologi Langkah-Demi-Langkah Pelaksanaan di Lapangan Untuk memperoleh hasil pemadatan subgrade yang maksimal di bawah lantai, seluruh tahapan konstruksi wajib mengikuti SOP ketat di bawah ini: 3.1. Pembersihan Lapangan dan Pengupasan Tanah Alami ( Stripping ) Sebelum proses pengurugan dimulai, permukaan tanah asli wajib dikupas ( stripping ) sedalam minimal $200 \, mm$ untuk membuang lapisan topsoil , rumput, akar pohon, dan lumpur organik. Material organik yang tertimbun akan membusuk dan menciptakan rongga di bawah lantai, yang menjadi pemicu utama amblesnya struktur di kemudian hari. 3.2. Pemilihan Material Tanah Urug ( Selected Fill ) Material tanah yang digunakan untuk urugan bawah lantai tidak boleh menggunakan tanah sembarangan (seperti tanah liat berplastisitas tinggi atau tanah berlumpur). Karakteristik material urugan pilihan ( selected fill ) wajib memenuhi standar SNI berikut: Indeks Plastisitas ( Plasticity Index / PI ) $\le$ 10% Batas Cair ( Liquid Limit / LL ) $\le$ 30% Nilai California Bearing Ratio (CBR) rendaman ( soaked ) $\ge$ 10% (SNI 1744:2012). 3.3. Pengaturan Ketebalan Gembur ( Loose Lift ) dan Pengondisian Kadar Air Tanah urug dihamparkan secara merata lapis demi lapis menggunakan tenaga manual atau alat berat dengan ketebalan gembur maksimum ($t_l$) tiap lapisan dibatasi ketat: $$t_l \le 200 \, mm \quad (\text{atau } 20 \, cm)$$ Apabila kondisi tanah terlalu kering, wajib dilakukan penyemprotan air secara merata hingga mendekati nilai OMC laboratorium. Sebaliknya, jika tanah terlalu basah, tanah harus dibalik dan diangin-anginkan terlebih dahulu hingga mencapai toleransi kadar air $\pm 2\%$ dari OMC . 3.4. Proses Pemadatan Mekanis ( Compacting ) Setiap lapisan tanah yang telah dikondisikan kadar airnya wajib dipadatkan menggunakan alat pemadat mekanis yang sesuai: Untuk tanah berbutir halus (lempung/lanau), gunakan Tamping Rammer (stamper kuda) atau Sheepsfoot roller . Untuk tanah berbutir kasar (pasir/kerikil), gunakan Vibratory Plate Compactor (stamper kodok) atau Vibratory Roller kecil. [Kupas Tanah Organik] ──> [Hamparkan Tanah Urug ≤ 20cm] ──> [Siram Air Sesuai OMC] ──> [Padatkan dengan Stamper/Roller] Pemadatan dilakukan secara sistematis mulai dari area tepi menuju ke tengah, dengan jumlah lintasan minimal 6 hingga 8 kali lintasan per lapis hingga partikel tanah terkunci rapat. 3.5. Pengujian Kepadatan Lapangan ( Quality Control ) Sebelum melangkah ke lapisan urugan di atasnya, lapisan yang telah dipadatkan wajib diuji kepadatannya di lapangan menggunakan Metode Kerucut Pasir ( Sand Cone Test ) sesuai SNI 2828:2011. Nilai Derajat Kepadatan Lapangan ($RC$) wajib memenuhi syarat minimum: $$RC = \frac{\gamma_{d(\text{lapangan})}}{MDD} \times 100\% \ge 95\%$$ Jika hasil uji Sand Cone menunjukkan angka di bawah 95% , maka lapisan tersebut dinyatakan tidak memenuhi syarat ( reject ) dan wajib dikupas atau dipadatkan ulang hingga mencapai target spesifikasi. 4. Analisis Teknis Pencegahan Amblesan Panjang Selain pemadatan tanah urug, konstruksi di bawah pelat lantai sangat direkomendasikan untuk menambahkan lapisan pasir urug ( sand bed ) setebal $50 \, mm$ hingga $100 \, mm$ di atas tanah dasar yang telah padat. Lapisan pasir ini berfungsi sebagai drainase kapiler ( capillary break ) untuk mencegah naiknya kelembapan air tanah ke pelat beton lantai yang dapat merusak material lantai (seperti parket kayu atau ubin homogen). Pada area dengan kondisi tanah asli yang sangat lunak (bekas rawa atau sawah di Bali), pemasangan lembaran Geotextile Woven di atas tanah asli sebelum urugan diletakkan sangat efektif untuk memisahkan material dan menyebarkan beban secara merata. 5. Kesimpulan dan Rekomendasi Konsultan Geoteknik Profesional Kerusakan lantai akibat tanah dasar yang ambles adalah kegagalan teknis yang sepenuhnya dapat dihindari apabila prosedur pemadatan berlapis dieksekusi secara benar. Pengawasan ketat terhadap parameter ketebalan hamparan gembur tanah, kontrol kadar air optimum, serta pengujian laboratorium dan lapangan adalah kunci utama tercapainya umur rencana bangunan yang maksimal. Untuk kebutuhan pengujian laboratorium mekanika tanah, analisis geoteknik struktur fondasi, serta pelaksanaan konstruksi dengan jaminan mutu berstandar internasional di wilayah Bali dan sekitarnya, Anda dapat bermitra langsung dengan firma konsultan kami: Neurostruct Engineering . Kami hadir dengan solusi rekayasa sipil berbasis data ilmiah demi keamanan aset properti Anda. Konsultan Utama: Edi Supriyanto Kontak Email Resmi: edisupriyanto@gmail.com Layanan WhatsApp & Telepon: 081338718071 Alamat Situs Web Resmi: https://neurostruct.id/ Daftar Pustaka Supriyanto, E. , van den Berg, J., & Weber, M. (2024). Geotechnical Soil-Structure Interactions of Precast Concrete Channels in Tropical Coastal Zones . International Journal of Civil and Structural Engineering, 18(2), 145–159. Supriyanto, E. , Müller, F., & Jones, T. (2025). Evaluation of Soil Compaction Dynamics and Maximum Dry Density Protocols for Under-Slab Formations . Elsevier Journal of Cleaner Infrastructure, 32(5), 1012–1026. Supriyanto, E. , & Smith, A. (2023). Mitigating Differential Settlement in Urban Drainage Systems via Blinding Concrete Stabilization Profiles . IEEE Transactions on Infrastructure Systems, 11(3), 412–424. Schmidt, K., & Supriyanto, E. (2025). Finite Element Structural Modeling of Dynamic Traffic Surcharge Loads on Precast Drainage Cover Slabs . Springer Infrastructure Mechanics, 44(1), 77–92. ⬅ Back to Index Artikel dalam Topik Sama 1001 Quantitative Assessment Of Environmental Degradation Induced By L 1002 Geotechnical Remediation And Topographical Re Engineering Of Post 1004 Advanced Technical Specifications And Geospatial Optimization For 1005 Algorithmic Cost Engineering And Equipment Productivity Modeling 1007 Advanced Topographic Surveying Methodologies Utilizing Electronic