Research the Integration of Geodetic and Geotechnical Methods in Monitoring the Horizontal Displacement of Diaphragm Walls

This article investigates the integration of geodetic and geotechnical methods for monitoringthe horizontal displacement of diaphragm walls. The results show that when the horizontal displacementis measured by the geotechnical method using an inclinometer sensor, the center point at the bottom ofthe guide pipe is usually chosen to be the origin to calculate displacements of the upper points. However,it is challenging to survey the bottom point for checking its stability directly. If this bottom point moves,the observation results will be incorrect. Thus, the guide pipe must be installed in the stable rock layer.But in the soft ground, this rock layer locates more deeply than the diaphragm walls, so the guide pipecannot be laid out at the required location. Geodetic methods can directly observe the displacement of thecenter point on the top of the guide pipe with absolute displacement values at high accuracy. Because thedisplacements of observation points are determined at stable benchmarks, these values are considered thepipe's displacement. Thus, an integrated solution allows the center point on the top of the pipe to be theorigin to calculate the displacements of different points located inside the diaphragm wall. Then, thecalculated values are calibrated back to the inclinometer observed values to achieve highly reliabledisplacement, which reflects the moving of diaphragm walls. An experiment integrating the geodetic andgeotechnical methods is conducted with an observation point at a depth of 20 meters at a construction sitein Ho Chi Minh city. The deviations of the top point that are observed by the two methods are -4.37millimeters and -3.69 millimeters on the X-axis and the Y-axis, respectively. The corrected observedresults prove that the integrated solution has a good efficiency in monitoring the horizontal displacementof diaphragm walls. The bottom point observed by an inclinometer is unconfident enough to choose to bea reference point.

The Thermal and Settlement Characteristics of Crushed-Rock Structure Embankments of the Qinghai-Tibet Railway in Permafrost Regions Under Climate Warming

The temperature difference at the top and bottom of the crushed-rock layer can drive the heat convection inside. Based on this mechanism, crushed-rock structures with different forms are widely used in the construction and maintenance of the Qinghai-Tibet Railway as cooling measures in permafrost regions. To explore the stability of different forms of crushed-rock structure embankments under climate warming, the temperature and deformation data of a U-shaped crushed-rock embankment (UCRE) and a crushed-rock revetment embankment (CRRE) are analysed. The variations in temperature indicate that permafrost beneath the natural sites and embankments is degrading but at different rates. The thermal regime of ground under the natural site is only affected by climate warming, while that under embankment is also affected by embankment construction and the cooling effect of the crushed-rock structure. These factors make shallow permafrost degradation beneath the embankments slower than that beneath the natural sites and deep permafrost degradation faster than that beneath the natural sites. Moreover, the convection occurring in the crushed-rock base layer during the cold season makes the degradation of permafrost beneath the UCRE slower than that in the CRRE. The faster degradation of permafrost causes the accumulated deformation of the CRRE to be far greater than that of the UCRE, which may exceed the allowable value of the design code. The analysis shows that the stability of the UCRE meets the engineering requirements and the CRRE needs to be strengthened in warm and ice-rich permafrost regions under climate warming.

Karakterisasi Geoteknik Fondasi Kandidat Tapak PLTN dengan Metode Seismik Refraksi

ABSTRAK. Pemerintah Indonesia dalam Peraturan Presiden (Perpres) Nomor 38 Tahun 2018 tentang Rencana Induk Riset Nasional Tahun 2017–2045, menetapkan beberapa bidang utama yang akan menjadi prioritas penelitian nasional, salah satunya adalah bidang energi. Dalam tema riset teknologi kelistrikan berbasis energi baru dan terbarukan rendah/nol karbon terdapat topik riset teknologi Pembangkit Listrik Tenaga Nuklir (PLTN) skala komersial. Pada topik riset tersebut, ditetapkan bahwa dalam jangka waktu penelitian tahun 2020–2024, dihasilkan purwarupa PLTN. Pada penelitian ini, karakterisasi geoteknik tapak PLTN dilakukan dengan menggunakan metode seismik refraksi guna melengkapi data penelitian sebelumnya. Tujuan penelitian ini adalah untuk mengetahui profil perlapisan batuan bawah permukaan untuk estimasi pekerjaan terkait fondasi PLTN. Pemetaan geologi dan akuisisi data geofisika, pengolahan, serta interpretasi tanah/batuan berdasarkan parameter kecepatan gelombang kompresi (Vp). Hasil pemetaan geologi menunjukkan adanya 2 satuan batuan beku yaitu diorit kuarsa dan andesit. Hasil pengolahan dan interpretasi data seismik refraksi menghasilkan model penampang Vp pada lapisan batuan bawah permukaan. Terdapat 3 lapisan batuan di lokasi penelitian yaitu lapisan tanah (Vp = 361–715 m/s), lapisan batuan beku lapuk (Vp = 1.386–2.397 m/s), dan lapisan beku segar (Vp = 3.789–6.133 m/s). Perkiraan densitas batuan beku segar berdasarkan perhitungan adalah 2,43–2,74 g/cm3. Hasil pemodelan dapat menunjukkan kedalaman dan struktur bawah permukaan lapisan batuan beku segar yang dapat menjadi fondasi bangunan PLTN.ABSTRACT. Presidential Regulation (Perpres) number 38 of 2018 concerning the National Research Master Plan for 2017–2045, the Government of Indonesia establishes several main areas that will become national research priorities, one of which is the energy sector. In the research theme of electricity technology based on new and renewable low/zero carbon energy, there is the topic of research on commercial-scale Nuclear Power Plant (NPP) technology. On the research topic, it was determined that within the research period of 2020–2024, a prototype nuclear power plant would be produced. Research related to the geotechnical characterization of the nuclear power plant site using the seismic refraction method was carried out to complement the previous research data. The purpose of this study was to determine the subsurface rock layer profile for estimation of work related to nuclear power plant foundations. Geological mapping and geophysical data acquisition, processing, as well as soil/rock interpretation based on the compression wave velocity (Vp) parameter are carried out to achieve this goal. The results of geological mapping show that there are 2 igneous rock units, namely quartz diorite and andesite. The results of processing and interpreting seismic refraction data produced a cross-sectional model of Vp in the subsurface rock layers. There are 3 rock layers in the research location, namely soil layer (Vp = 361–715 m/s), weathered igneous rock layer (Vp = 1.386–2,396 m/s), and fresh igneous layer (Vp = 3.789–6.133 m/s). The estimated density of fresh igneous rock based on calculations is 2.43–2.74 g/cm3. The modeling results can show the depth and structure of the subsurface layer of fresh igneous rock that can be the foundation of nuclear power plants.

Habitat Preference Modeling of Prehistoric Giant Shark Megalodon During Miocene in Bentang Formation of West Java Coast

In the Miocene era about 20 million years ago, the South Coast of West Java was a sea and habitat for marine organisms including giant sharks Megalodon measuring about 18 meters long. This study aimed to model the habitat preference of the prehistoric gigantic shark Otodus megalodon population based on the fossil record. From fossil teeth, it revealed that the rock layer where the teeth found was Bentang formation from Miocene era. Many fossils of Megalodon had been unearthed from Bentang formation which is part of the South Coast of West Java. The habitat model was developed using the Sea Level Rise Inundation Tool of ArcGIS to estimate the sea depth and Megalodon’s habitat during the Miocene. The length of the teeth of O. megalodon found was ranged from 13 to 19 cm, indicating the presence of juvenile and adult O. megalodon. Based on the model, in the Miocene era, half of West Java was a sea with a depth ranging from 0 to 200 meters. At that time, it was estimated that juvenile O. megalodon occupied waters with a depth of 0-40 meters with an area of 1365 km2. Meanwhile, adult O. megalodon prefers a depth of 80-160 m and the frequency of habitat use increases at a depth of 200 m. The declining population of O. megalodon is associated with climate change and declining prey populations.

Ground Pressure under Mining Ore Bodies of Different Angles Based on Physical Simulation

Ground pressure characteristics of the ore body and the overburden deformation of the stope depend highly on the combined influence of geological conditions and mining disturbance. The ore body inclination, as a natural geological factor, has a nonnegligible effect on the underground mining. The ore angle plays a great role in the stress distribution of the overlying rock layer, resulting in the movement and destruction of the rock layer. The variation of the ore angle dominates the stress distribution of the overburden rock, the forms of movement, destruction, and the surface moving basin. Here, taking the geological mining conditions of the deep ore body mining in Jinning Phosphate Mine as the engineering background, we adopt a similar material ratio scheme of each rock layer in the mining area via the similarity theory and the principle of orthogonal experiment. We conduct systematic study on the strata movement, mining failure characteristics, and movement of the overlying rock in stope using a similar simulation test under two different ore angles of 20° and 50°. We found that, as the ore body inclination increases from 20° to 50°, the overburden unloading area of the stope extending to the deep part of the rock layer in the vertical direction is more obvious and its shape is more asymmetric about the stope center. The unloading area is more concentrated in the middle and upper part of the stope, while the upward development trend is more obvious. The relevant results can provide a certain reference for the underground mining of the mines and those with similar conditions.

Study on the Geological Condition Analysis and Grade Division of High Altitude and Cold Stope Slope

Analysis of the geological conditions of high-altitude and low-temperature stope slopes and the study of grade division are the basis for the evaluation of slope stability. Based on the engineering background of the eastern slope of the Preparatory iron mine in Hejing County, Xinjiang, we comprehensively analyse and summarize the factors that affect the geological conditions of high-altitude and cold slopes and finally determine nine geological conditions that affect the index parameters. Based on a back-propagation (BP) neural network algorithm, we establish an applicable network model to analyse the geological conditions of slopes in cold areas. The model is applied to the eastern slope to analyse and classify the geological conditions of the high-altitude and low-temperature slopes. The research results show that the skarn rock layer in the eastern slope is in a stable state and not prone to landslides, and its corresponding geological condition is Grade I; meanwhile, the monzonite porphyry rock layer is in a relatively stable state, with a potential for landslides and a corresponding geological condition Grade II. The marble rock layer is in a generally stable state, there is the possibility of landslide accidents, and the corresponding geological condition level is Grade III. The limestone rock layer is in an unstable state and prone to landslide accidents, it has a corresponding geology condition Grade IV. Therefore, the eastern slope can be divided into different geological condition regions: Zone I, Zone II, Zone III, and Zone IV, and the corresponding geological condition levels for these are Grade I, Grade II, Grade III, and Grade IV. These results may provide a basis for the stability evaluation of high altitudes and cold slopes.

Force Chain Effect of Deep Foundation Pit Supported by Soldier Piles in the Sand-Gravel Layer

Soldier pile support is an important tool for supporting deep foundation pits in the sand-gravel layer. However, since the sand-gravel layer itself is an aggregate of particles, its noncontinuity will cause extremely complex changes in the properties of the surrounding soils during pile supporting, and the changes in the mechanical properties of the soil behind the piles can also affect the safety and stability of the pit. To study the changing pattern of the surrounding soil in the course of pile supporting, we used the numerical method to simulate an excavation in the sand-gravel layer, followed by an analysis of the movement and stress distribution of the surrounding rocks. A photoelastic experiment was carried out to simulate the excavation process and study the force chain network of the surrounding soil as well as its changing characteristics. As shown by the results, (1) during the excavation of a deep foundation pit supported by soldier piles, on the same horizontal plane, the force chain changed most dramatically at the position that was 13.8 m (depth of the foundation pit) away from the edge of the foundation pit; (2) during the excavation, the force chain structure of the surrounding soil changed from vertical development to both vertical and horizontal developments; when there was a hard rock layer at the bottom of the soldier piles, the supporting effect of the piles was mainly provided by the hard rock layer; (3) the free face should be reinforced, and the excavation face should be adjusted based on the underground conditions of surrounding buildings (structures).

Study on Supporting Protection of Tunnel Opening near a Rock Layer under Elastic Deformation of Surrounding Rock

Due to the limitation of geological conditions and route alignment, tunnel engineering will inevitably pass through special sections such as shallow buried section, broken rock layer, and loss and weak rock stratum. Tunnel construction in these special sections will easily lead to tunnel collapse, landslide of portal slope, excessive deformation of supporting structure, and even deformation and damage accidents, which are high-incidence areas of engineering safety accidents. In this paper, a 3D numerical model is established based on a practical engineering to analyze the deformation and stress variation of surrounding rock of the tunnel with the in-advance support technology. According to the monitoring results of the actual project, the deformation law of the soft rock section at the tunnel entrance is mastered. The deformation of surrounding rock of the tunnel under the support condition of changing the three main parameters, such as ring spacing, pipe diameter, and pipe length, is analyzed, and the effect of controlling the deformation of surrounding rock with different parameters is studied. The deformation, stress characteristics, and plastic zone distribution of surrounding rock by a single side wall guide method and ring excavation and retaining core soil method in advance support are numerically simulated and studied.