Determination of Residual Shear Strength from Reversal Direct Shear test: Analysis and Recommendation

Reversal Direct Shear test is used for the determination of residual shear strength of soil sample. This test was conducted on undisturbed and remolded sample of embankment slope of Pa Bon Dam, Thailand that had failed after operating for 10 years. The undisturbed sample was taken from the downstream slope (non-failure zone) while the remolded sample was taken from the upstream slope (failure zone). The results yielded identical values of residual strength parameters. On the basis of laboratory test, various recommendations are proposed for the conduction of this test in future.

Segregation Peat Fiber and Pre- Consolidation Pressure Effect on the Physical Properties of Reconstituted Peat Soil

The preparation of the undisturbed peat sample at the site must be conducted to understand its characteristics. However, the sampling process becoming difficult due to the condition of peat soils itself. Due to the limitation in gaining undisturbed sample, a study on reconstitution sample becoming more popular in term of investigating the properties of soil that represent the real site condition. The main purpose of this paper was to investigate the physical properties of undisturbed and reconstituted peat RS3.350, RS2.360, RS1.000 and RS0.425. In this study, the segregation of peat and expulsion water with the aids pre-consolidation pressure was applied to the reconstituted sample. The range value of the physical properties of reconstituted peat was varied from each type of peat classification which affected by the segregation fiber and pre-consolidation pressure effect method. The entire reconstituted peat samples were recons passing the opening sieve size 3.350mm, 2.360mm, 1.000mm and 0.425 mm and were subjected with the 50 kPa, 80 kPa and 100 kPa pre-consolidation pressures. As a result, the natural Parit Nipah peat soil was classified as hemic peat (H5). The percentage of water content, liquid limit, organic content and fiber content for the reconstituted sample is lower compared to the undisturbed peat sample; but differed from specific gravity where the percentage for the reconstituted sample was higher than the undisturbed sample. Conclusively, the segregation of peat fiber and pre-consolidation pressure methods greatly affect and change the physical properties of peat samples.

Karakterisasi Durabilitas Batulempung Menggunakan Uji Indeks Disintegrasi; Studi Kasus pada Lokasi Rencana Jalan Tol Cisumdawu di Daerah Ujungjaya, Sumedang, Jawa Barat

Batulempung seringkali mudah hancur dalam periode singkat ketika tersingkap ke permukaan dan atau saat berinteraksi dengan air. Hal ini dapat memicu beberapa permasalahan di dalam kegiatan rekayasa. Salah satu kegiatan rekayasa yang sedang dan akan berjalan adalah pembuatan Jalan Tol Cisumdawu (Cileunyi-Sumedang-Dawuan) yang merupakan akses penghubung wilayah-wilayah di sekitar Bandung dan Cirebon. Akses jalan ini juga akan terhubung dengan Bandara Internasional Jawa Barat (BIJB) di Kertajati. Bagian ruas jalan ini di daerah Ujungjaya, Sumedang akan melintasi Formasi Subang dan Kaliwangu yang memiliki litologi utama berupa batulempung. Karakterisasi durabilitas jenis batuan ini penting dilakukan untuk menunjang aspek teknis kegiatan rekayasa di sekitar area tersebut. Metode penelitian yang digunakan adalah pengambilan sampel tak terganggu (undisturbed sample) di lapangan, uji pembasahan dan pengeringan (wetting-drying) di laboratorium berupa uji indeks disintegrasi, uji mineralogi lempung melalui difraksi sinar X (XRD), dan uji sifat-sifat fisik batuan yang mencakup kadar air alami, densitas kering, porositas, dan absorbsi. Hasil penelitian menunjukkan indeks-indeks durabilitas batulempung dalam penelitian ini tergolong rendah. Disintegrasi batuan berlangsung cepat dan menunjukkan perilaku body slaking. Faktor-faktor yang berpengaruh kuat terhadap durabilitas batulempung terdiri dari porositas dan absorbsi. Hubungan porositas dan absorbsi dengan indeks durabilitas (rasio disintegrasi) mengikuti suatu kurva eksponensial negatif. Rasio disintegrasi cenderung turun seiring kenaikan nilai porositas dan absorbsi batulempung.

The Analysis of Slope Safety Factors at Post Mining Areas in Semaya Village, Randudongkal Sub-district, Pemalang

Mining activities has become increasingly widespread in recent years, especially people’s mining, thatjust concerned about the result and not paying attention to the environmental factors.This is causedthe post mining area’s destruction and environmental degradation potential. For this reason, the slopesafety factor enhancement analysis on the post mining area in Semaya Village, Randudongkal Sub-District, Pemalang Regency is needed. Slope stability analysis using Slide 6.0 software to identify thecondition of post mining area from the results of undisturbed sample (UDS) laboratory data.Laboratory testing includes several aspects including water content, weight, specific gravity, grain size,atteberg limit test, and direct shear test. The value of the safety factor is 1,441, the value is in the safecategory because it passes the minimum value limit of the safety factor which is 1.25, this result isobtained from the terracing modeling.

Modeling heat transfer process in soils

In this paper, a new model is presented for calculating the thermal conductivity of soils, and the main provisions for the derivation of analytical formulas are given. The presented model allows taking into account the density, moisture content and temperature of the soil base. The technique presented in the paper makes it possible to dispense with laborious experiments to estimate the thermal conductivity of the soil. The method of analytical calculation is step by step presented in the paper. Two variants of using the method are proposed: 1) Less accurate method, for preliminary evaluation, without the need to take probe and conduct experiments. 2) More accurate method, with at least one experiment with a disturbed or undisturbed sample. The results of comparison of calculated values of thermal conductivity and experimental data are presented.

Can Soil Penetration Resistance and Bulk Density Be Determined in a Single Undisturbed Sample?

Soil quality indicators such as penetration resistance (PR) and bulk density (BD) are traditionally determined in a single undisturbed soil sample. The aim of this study was to assess the effect of PR measurements of undisturbed samples on the determination of BD in the same sample of two soils differing in clay contents. To this end, samples were collected from the 0.00-0.10 and 0.10-0.20 m layers of two soils of clayey and very clayey texture. Volumetric rings were used to collect a total of 120 undisturbed soil samples from each soil layer that were divided into two subsets containing 60 units each. One sample set, designated “perforated samples”, was used to determine PR and BD in the same undisturbed sample; the other, named “intact samples”, was used to determine BD only. Bulk density values for perforated and intact samples were compared by analysis of variance, using a completely randomized experimental design. Means were compared by the t-test at 5 %. The BD values for the clayey soil were similar in perforated and intact samples from the two layers. However, BD of the very clayey soil was lower in the perforated than in the intact samples at both depths. Therefore, PR and BD in clayey soils can be accurately determined in the same undisturbed sample whereas in very clayey soils, different samples are required for this purpose.

Erosion processes in black marl soils at the millimetre scale: preliminary insights from an analogous model

To investigate the millimetre-scale surface processes caused by natural rainfall, an undisturbed sample of badlands soil (1 m long, 0.5 m wide and 0.15 m thick) was carefully extracted. The sample is composed of black marl soil from a badlands area of the Draix Observatory (SE France). After extraction, the undisturbed sample was placed at the same slope angle (45°) as its original orientation and was then monitored for several processes via a terrestrial laser scanner (TLS) with millimetre-scale accuracy and resolution. This experiment identified several surface processes interpreted as micro-landslides, swelling of the black marl material and lateral expansion that closed desiccation cracks. These micro-processes illustrate the complexity of the surface micro-topography changes that control erosion and infiltration rates over time.

A New Type of Muddy Sediment Undisturbed Gravity Sampler in Shallow Waters

Muddy sediment records environmental change information water experienced. Due to the sampling disturbance, parameters provided by sediment analysis can't truly reflect the true nature of in situ sediment and water environmental information. This paper introduces a kind of muddy sediment undisturbed gravity sampler used in shallow waters, through a unique rubber sealing membrane deformation method. The sampler proved to be an effective tool of muddy sediment undisturbed sample in shallow waters, with characteristics of light weight, easy to carry, and convenient operation.