Surface Collapse Research Articles

Low Solids Emulsion Gels Based on Nanocellulose for 3D-Printing.

Multiphase (emulsion) gels with internal phase fractions between 0.1 and 0.5 were formulated at low loadings of cellulose nanofibrils (CNF), alginate, and polylactide (PLA). Their properties (rheology and morphology) fitted those of inks used for direct ink writing (DIW). The effect of formulation and composition variables were elucidated after printing cubic scaffolds and other solid designs. The distinctive microstructures that were developed allowed high printing fidelity and displayed limited shrinkage after room temperature and freeze-drying (0 and 5% shrinkage in the out-of-plane and in-plane directions upon freeze-drying, respectively). The CNF added in the continuous phase was shown to be critical to achieve rheology control as an effective interfacial stabilizer and to ensure the printability of the ink toward high structural reliability. We found that the extent of shape retention of the dried scaffolds resulted from the tightly locked internal structure. The PLA that was initially added in the nonpolar or organic phase (0 to 12%) was randomly embedded in the entire scaffold, providing a strong resistance to shrinkage during the slow water evaporation at ambient temperature. No surface collapse or lateral deformation of the dried scaffolds occurred, indicating that the incorporation of PLA limited drying-induced shape failure. It also reduced compression strain by providing better CNF skeletal support, improving the mechanical strength. Upon rewetting, the combination of the hydrophilicity imparted by CNF and alginate together with the highly porous structure of the 3D material and the internal microchannels contributed to high water absorption via capillary and other phenomena (swelling % between ∼400 and 900%). However, no shape changes occurred compared to the initial 3D-printed shape. The swelling of the scaffolds correlated inversely with the PLA content in the precursor emulsion gel, providing a means to regulate the interaction with water given its low surface energy. Overall, the results demonstrate that by compatibilization of the CNF-based hydrophilic and the PLA-based hydrophobic components, it is possible to achieve shape control and retention upon 3D printing, opening the possibility of adopting low-solids inks for DIW into dry objects. The dryable CNF-based 3D structural materials absorb water while being able to support load (high elastic modulus) and maintain the shape upon hydration.

Update of the German S3 guideline on atraumatic femoral head necrosis in adults

The update of the German S3 guideline on atraumatic femoral head necrosis in adults aims to provide an overview of diagnosis and treatment. All clinical studies, systematic reviews, and meta-analyses published in German or English between 01.05.2013 and 30.04.2017 were included. Of 427 studies, 28 were suitable for analysis. Risk factors are corticosteroids, chemotherapy, kidney transplants, hemoglobinopathies, and alcoholism. Differential diagnoses are for example bone marrow edema, insufficiency fracture, and destructive arthropathy. Radiography should be performed upon clinical suspicion. In patients with normal radiography findings but persistent complaints, magnetic resonance imaging (ARCO classification) is the method of choice. Computed tomography (CT) can be used to confirm/exclude articular surface collapse. Asubchondral sclerosis zone >30% in CT indicates a better prognosis. Left untreated, asubchondral fracture will develop within 2years. The risk of disease development in the opposite side is high during the first 2years, but unlikely thereafter. In conservative therapy, iloprost and alendronate can be used in a curative approach, the latter for small, primarily medial necrosis. Conservative therapy alone as well as other drug-based and physical approaches are not suitable for treatment. No particular joint-preserving surgery can currently be recommended. Core decompression should be performed in early stages with <30% necrosis. From ARCO stageIIIc or in stageIV, the indication for total hip arthroplasty should be checked. Results after total hip arthroplasty are comparable with those after coxarthrosis, although the revision rate is higher due to the relatively young age of patients. Statements on the effectiveness of cell-based therapies such as expanded stem cells or bone marrow aspirates cannot currently be made.

Cutter-disc consumption during earth pressure balance tunnelling in mixed strata

The wear of excavation tools is considered to be one of the critical factors affecting the scheduling of shield tunnel construction. There is presently no effective countermeasure to prevent severe wear of excavation tools during tunnelling operations in complex geological formations. In addition, such wear is likely to lead to other problems, such as face instability and an unfavourable rate of tunnel advancement. The study reported in this paper analysed the various factors that affected the wear and performance of excavation tools during earth pressure balance machine tunnelling at the Ma-Lian section of line 9 of the Guangzhou metro, China. It was found that tunnelling in mixed ground conditions (upper soft and lower hard strata) led to severe wear of the cutter discs, resulting in additional costs and schedule delays. The foam expansion ratio, concentration of foaming agent and the foam injection ratio were measured to be 20, 2·5% and 40% respectively. Pre-grouting and effective soil conditioning were also found to prevent excessive wear of the cutter discs and surface collapse incidents caused by face instability.

Collapse mechanism of the overlying strata above a salt cavern by solution mining with double-well convection

In solution mining of salt formations, unreasonable salt cavities formed may lead to surface collapse hazards. In this paper, a mathematical model was proposed to analyze the collapse mechanism of the overlying strata above a salt cavern induced by solution mining with double-well convection. In the proposed model, the collapses of the overlying strata were supposed to occur layer by layer, and a thin plate with four edges clamped was introduced to calculate the critical collapse span of each layer. The limit breaking distance of the thin plate can be solved by setting the corresponding surrounding condition. According to the solution, the limit breaking distance is related to the dimensions, the mechanical properties of the rock, the buried depth, and the force status. For the convenience of calculation, a span criterion was introduced to distinguish the limit breaking distance. To keep the immediate roof more stable, the span criterion should be larger. As a case study, the collapse incidents at Dongxing Salt Mine were analyzed by the proposed model, and the collapses were verified to be inevitable under its mining and geological conditions. Discussions were finally carried out to study the influences of the thickness of the immediate roof, tension strength, Poisson ratio, and buried depth on the collapses. Above all, the collapses will occur more easily with the decrease of the thickness, tension strength, and Poisson ratio of each stratum. Especially, the collapse depth will not increase linearly with the buried depth, because of the bulking effect of the overlying strata.

Single medial approach for the treatment of Schatzker IV tibial plateau fractures

Objective Try to treat the Schatzker Ⅳ tibial plateau fractures with a single medial approach. Methods A single medial longitudinal incision was used to treat 16 cases of Schatzker type Ⅳ tibial plateau fractures admitted to hospital from January 2013 to January 2016 which diagnosed by computed tomography (CT). The range of peeling up to the anterior edge of the tibia, the back side skipping over the posterior bone crest to expose the Posterior surface, persisting the joint capsule and the medial collateral ligament, and the far end reached 3-5 cm beyond the fracture line. As the lower limbs in the situation of external rotation with hip and knee flexion, open the medial fracture, using a strutting forceps to brace the bone block, made out he collapsing cartilage and subchondral bone which belong to de back column, Using the detacher to lift the subchondral bone together with the cartilage surface, lift up to the lateral side until it can’t be raised again, fixed them with 2-3 Kirschner-pins of 1.5 mm-diameter. And then used a large C type Matta forceps to clamp the fracture line for recovering the width of tibial platform. A Tomofix plate was used to fix the fracture in the position of posterior bone crest. The intercondylar eminence fracture of the anterior cruciate ligament was fixed under direct vision, and the supporting plate was placed in the posterior medial wall to fix the posterior medial small fracture. The standard X-ray films of bilateral knee joint were taken and compared after the operation. The knee joint activity was measured at 1 year follow-up after 1 years. The healing of subchondral fracture and no secondary collapse were performed by plain scan, and the function of the knee joint was evaluated by Lysholm scoring system. Results 15 cases were followed up for more than 1 years. All the X-ray showed fracture healing at half a year. CT confirmed that the fracture healed completely at the time of reexamination. The condylar crest avulsion fracture healed well, there was no secondary cartilage surface collapse, no obvious osteoarthritis, the average knee joint activity was 118°, and the average of Lysholm score was 87. Conclusion Combined approach is an effective method for the treatment of complex tibial plateau fractures, but for Schatzker Ⅳ fractures, a good reduction can be achieved with a single medial approach combined with some proper tools. Key words: Tibial plateau fractures; Medial approach; Schatzker Ⅳ

TYPICAL APPLICATIONS OF AIRBORNE LIDAR TECHNOLAGY IN GEOLOGICAL INVESTIGATION

Abstract. The technology of airborne light detection and ranging (LiDAR), also referred to as Airborne Laser Scanning, is widely used for high-resolution topographic data acquisition (even under forest cover) with sub-meter planimetric and vertical accuracy. This contribution constructs the real digital terrain model to provide the direct observation data for the landscape analysis in geological domains. Based on the advantage of LiDAR, the authors mainly deal with the applications of LiDAR data to such fields as surface land collapse, landslide and fault structure extraction. The review conclusion shows that airborne LiDAR technology is becoming an indispensable tool for above mentioned issues, especially in the local and large scale investigations of micro-topography. The technology not only can identify the surface collapse, landslide boundary and subtle faulted landform, but also be able to extract the filling parameters of collapsed surface, the geomorphic parameters of landslide stability evaluation and cracks. This technology has extensive prospect of applications in geological investigation.

Investigation on the characteristics of overlying strata caving in the Chengchao Iron Mine, China

In this study, a comprehensive assessment of the overlying strata caving characteristics of mental mines is conducted for the non-pillar sublevel caving method, especially considering the geological features and rock mass characteristics. In general, the overlying strata caving process can be divided into four stages: the intermittent roof caving stage, the crack extension and surface subsidence stage, the karst collapse stage, and the mining-induced collapse stage. Roof caving is an intermittent process, with higher caving occurring in stronger rock masses, and occurs more easily in weaker rock masses. Due to gaps generated in the overlying rock mass, the bulking coefficient of the overlying strata is much greater than the laboratory-measured value; it also varies with the mining advance lines. During the crack extension and surface subsidence stage, the surface deformation is less extensive when the rock strength is greater, and the gradient of surface deformation is lower when the rock mass integrity is lower. Thus, higher mining height and lower rock mass quality result in greater surface deformation. Furthermore, weak planes, such as faults and joints, can help to generate fissures in weathered rock masses; these fissures create passageways for groundwater flow, which accelerates crack extension and connection in reverse. In addition, surface collapses can be divided into karst collapses and mining-induced collapses. Because a large number of fissures and a high karst rate create favorable conditions for karst collapse, significant variations in groundwater levels can induce karst collapse at the surface, with high negative pressure forming in the karst caves. Mining-induced collapses are mainly related to the mining depth, mining height, and the properties of the overlying rock mass. Underground mining is a major factor in surface collapse, and heavy rainfall can induce a delayed but sudden collapse.

Early-stage osteonecrosis of the femoral head: where are we and where are we going in year 2018?

Osteonecrosis of the femoral head (ONFH) is a devastating condition affecting relatively young patients whereby the femoral head is necrotic, resulting in significant pain, articular surface collapse, and eventual osteoarthritis. This condition has been highly associated with chronic steroid use, alcoholism, and hip trauma, as well as other less common conditions. Without intervention, this condition has a high likelihood of progressing and developing into end-stage osteoarthritis. Unfortunately, ONFH is difficult to diagnose on plain radiographs in the early stages of the disease, and often requires more advanced imaging modalities such as MRI in order to fully assess for early degeneration. Providers, therefore, must have a high index of suspicion when a younger patient presents with hip pain and negative X-rays. Unfortunately, in patients whose femoral heads have already collapsed, joint-preserving procedures are not effective, and total hip arthroplasty remains the most reliable long-term treatment. Multiple treatments have been pursued to address osteonecrosis in patients whose femoral head have not yet collapsed, but the results of these treatments are mixed. The most promising of these interventions to date is core decompression with the use of concentrated bone marrow aspirate to improve the healing potential of the femoral head. Further studies including randomized clinical trials are necessary in order to assess the effectiveness of this therapy, the best possible source of cells and the best method of implantation in order to further improve results in those with pre-collapse ONFH.

Application of domestic high-resolution satellite imagery data to the investigation of surface collapse in the Tiechanggou coal mine of Xinjiang

Application of domestic high-resolution satellite imagery data to the investigation of surface collapse in the Tiechanggou coal mine of Xinjiang

Inefficacy of autologous bone marrow concentrate in stage three osteonecrosis: a randomized controlled double-blind trial.

The fracture stage of non-traumatic osteonecrosis (ON stage 3) of the femoral head (ONFH) has an unfavourable prognosis frequently requiring total hip replacement (THR). The percentage could be lowered after core decompression. In earlier non-fracture ON stages, implantation of autologous bone marrow aspirate concentrate (BMAC) improved the effect of core decompression. The purpose was to evaluate the effect of BMAC in addition to core decompression in stage 3 ONFH. A double blind RCT was conducted comparing two groups: core decompression plus saline injection or core decompression plus BMAC implantation. Both patients and assessors were blinded to the treatment assignments. Evaluations were done at baseline, three, six, 12, and 24months, including pain (VAS), WOMAC, side-effects, radiological evolution including ARCO subclassifications, together with possible THR requirement. The primary endpoint was the need for THR. The second endpoints included the clinical symptoms such as pain and functional ability and the progression of the ON lesions as well as the appearance of osteoarthritis features (ARCO stage 4). Both groups included 23 hips (19 patients). No differences were found between the groups for THR requirements, clinical tests, and radiological evolution. In both groups, 15/23 hips needed THR. The radiological evolution of the ONFH lesions in term of location, extension, surface collapse, and dome depression was moderate in both groups and was not correlated with the need of THR. Implantation of BMAC after core decompression did not produce any improvement of the evolution of ONFH stage 3. Level of evidence I.

Double-plate fixation via combined approaches for the treatment of old tibial plateau fractures of Schatzker type IV

To explore the clinical efficacy of double-plate fixation for the treatment of old tibial plateau fractures with Schatzker type IV through anterior midline and posteromedial approaches. From July 2013 to July 2015, 15 patients with old tibial plateau fractures were treated with internal fixation using locking reconstructive plate for the posteromedial fragment and anatomical locking plate for anteromedial fragment through antero midline and posteromedial approaches. There were 9 males and 6 females, with an average age of 49.2 years old (ranged, 21 to 61 years old). Eight patients had injured in the left side and 7 in the right side. According to Schatzker classification, all patients were type IV. The mean interval from injury to operation was 26.5 days (ranged, 21 to 65 days). The main clinical symptoms before operation were knee joint swelling, pain, deformity and limitation of motion. The X-ray and CT confirmed the fracture type. The indexes such as tibial plateau tibial shaft angle (TPA), femoral tibial angle (FTA) and posterior slope angle (PSA) were compared between immediate postoperation and final follow-up using postoperative X-ray film. The knee functions were evaluated using the HSS (Hospital for Special Surgery) knee score system. Two patients had incision complications which healed by correct treatment, 1 patient had traumatic arthritis. All patients were followed up for mean 16.6 months (ranged, 13 to 24 months). No infections, deep venous thrombosis, implant loosening and breakage, fragment displacement, plateau surface collapse and bone nonunion found. The bone union time ranged from 3 to 8 months (mean 6.07 months) after operation. The average immediate postoperative value of TPA, FTA and PSA were(86.81±1.67)°, (168.00±3.29)° and(10.20±1.47)° respectively; and(86.47±1.67)°, (168.53±3.03)° and (10.54±1.21)° respectively at the final follow-up evaluation, showing no statistical differences(P>0.05). According to the HSS score system, 26.33±3.86 in pain, 20.00±1.79 in function, 16.00±1.55 in range of motion, 8.67±0.94 in muscle strength, 8.53±1.67 in flexion deformity, 9.33±0.94 in joint stability, and the total mean score was 88.86±8.92. The outcomes were excellent in 10 cases, good in 4, and fair in 1. Double-plate fixation via combined anterior midline and posteromedial approaches is an ideal surgical method for old tibial plateau fractures with Schatzker IV type, showing satisfactory exposure, reliable reduction and fixation, and benefiting for early functional exercise. The short-term clinical results was satisfactory.

The mechanism of hysteretic ground settlement caused by shield tunneling in mixed-face conditions

Shield is used more and more widely, such as coal mine roadway, hydropower tunnel, traffic tunnel and so on. But Tunneling with a tunnel boring machine (TBM) may cause inevitable ground subsidence. Though over the world numerous researches have been conducted for surface settlement induced by TBM in soft ground, the researches of surface settlement induced by TBM in a sandy cobble stratum are limited and a comprehensive study of the mechanism of delayed settlement induced by TBM in a sandy cobble stratum is unavailable. A ground stable state or surface settlement can be determined based on real-time monitoring data for surface dynamic subsidence. Subsequently, TBM tunneling parameters can be adjusted to accommodate various geological conditions. A sand-pebble-soil matrix is a typical heterogeneous material. The macro-mechanical performance of this matrix significantly differs from any material. In a general situation with a low water level and minimal disturbance, a stratum can stabilize by itself for a long period of time. Considering the characteristics of the stratum, ground loss can be divided into two phases: immediate settlement, which tends to stabilize, and delayed settlement, which tends to occur in sand-cobble strata, where settlement develops at a much slower rate than in single-medium strata. Monitoring data is not sufficient to guide the construction in the case of delayed settlement. Cobble-soil matrix can be treated as a spatial structural system that is constituted by single granular soil, aggregates of granular soil and pebble grains. Based on Particle Flow Code in 2 Dimensions (PFC2D), the mechanical characteristics of the matrix and the TBM tunneling process were numerically simulated. Movements of the pebble grains were traced and recorded in real time. The model addressed the mechanism of surface collapse from the perspective of mesomechanics. According to the model, a matrix formed self-stabilizing arch that overlies an underground cavity seems gradually wear out with expanding the cavity and eventually penetrating to the ground surface. The law of ground movement and the formation mechanism of ground subsidence in TBM advancement were investigated. The main factors that affect surface subsidence are the speed of advancement, the underground water level and the supporting period. In the numerical analysis, the surface-loss lag was reproduced and the field monitoring data were verified. The findings of this study provide a new method for investigating ground subsidence in similar strata.

Effectiveness of unicompartment allografts replacement for bone tumor around the knee

To analyze the effectiveness of unicompartment allografts replacement for reconstructing bone defect after bone tumor resection around knee. Between January 2007 and January 2014, a total of 9 patients received unicompartment allografts replacement to treat bone tumor around the knee, including 6 males and 3 females, with an average age of 25.8 years (range, 17-38 years). There were 7 patients with bone giant cell tumor (postoperative recurrence of bone giant cell tumor in 1 case) and 2 patients with chondromyxoid fibroma. The tumors were located at the distal femur in 7 cases and proximal tibia in 2 cases, and the tumors were almost at the lateral limbs. The symptom duration was 2-5 months (mean, 3.2 months). The size of lesion ranged from 6 cm×2 cm to 9 cm×4 cm by X-ray film and MRI; and the metastasis was excluded by CT. The length of the allograft was 8.0-9.2 cm (mean, 8.6 cm). The intraoperative blood loss volume was 400-550 mL (mean, 480 mL); and 0-3 U of erythrocyte was transfused after operation. The continuous exudate of incision occurred in 1 patient, and cured after 3 months; the other incisions healed primarily at 2 weeks after operation. All patients were followed up 3-10 years (mean, 6 years). No operation area infection, allograft bone poor healing or rupture was found. At 1 year after operation, the knee range of motion was 90-110° (mean, 100°); the Musculoskeletal Tumor Society score was 24-29 (mean, 26). Low density area (osteolysis) was found in 6 allografts; no articular surface collapse, hairline fracture, or fracture was found in patients; callus formation was observed in the contact surface between the allograft and the host bone, and the cortical bone showed good continuity. Unicompartment allografts replacement can provide good support and function in terms of bone tumor resection, and achieve good effectiveness by biological reconstruction.

A mechanism for comet surface collapse as observed by Rosetta on 67P/Churyumov-Gerasimenko

A mechanism for comet surface collapse as observed by Rosetta on 67P/Churyumov-Gerasimenko

Mechanism of Surrounding Rock Failure and Crack Evolution Rules in Branched Pillar Recovery

To study the mechanism of surface collapse and crack evolution in a roadway chain failure process in the pillar recovery of Hongling lead zinc ore in Inner Mongolia Province, China, microseismic monitoring technology, moment tensor theory, and numerical simulation are used for the inversion of rock mass fracturing, the destruction type classification of crack, and the mechanism of surrounding rock. Research shows the following: (1) the rock mass fracturing is first produced within the +955 m level, before extending through the hanging wall to the ground surface. Then, many shear failures occur in the ground surface of the footwall, extending downwards in an arc-shaped path to the +905 m level. Finally, the surface gradually collapses with large-scale shear failures. (2) The mechanism of surface collapse is as follows: after the recovery of pillars in the +905 m level, tensile cracks generated in the top of orebody #2 extend upwards and obliquely. Analogously, shear cracks are generated in the top of orebody #1, extending upwards. After the recovery of pillars in the +855 m level, the marble interlayer is destroyed and sinks, and many tensile cracks and shear cracks exist and incise in the ground surface, which cause the ground surface to collapse. (3) The mechanism of crack evolution is as follows: after the recovery of 5107 pillars, the footwall haul road in the +905 m level was damaged and collapsed by the cut-through cracks. Those cracks then continue to extend upwards and converge with the slanting shear cracks in the +905 m level, which form a triangular failure in the footwall rock. Finally, the failure causes the tensile and shearing cracks in the haulage way of the +955 m level to extend and connect, which forms the haulage way chain failure.

Characteristics of nanoporous silica aerogel under high temperature from 950 °C to 1200 °C

Silica aerogel is a unique three-dimensional nano-porous material and its characteristics have attracted much attention from both engineers and researchers. However, their structural behaviors under high temperature are not well known yet. The structure of silica aerogel under high temperature from 950°C to 1200°C was investigated based on pycnometry, scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction patterns (XRD). It was obtained that the structure of silica aerogels was strongly affected by heating temperature and time. It was known based on experimental results that the changes of silica aerogel during 950–1200°C can be divided into three steps: expansion of primary particles at sample surface (step I), atrophy and pore collapse of primary particles at the surface (step II), and atrophy and pore collapse of primary particles inside the sample (step III). Change rate was found significantly dependent on the moving rate of expansion region, while during the first two steps only limited changes were observed about three dimensional nanoporous structures. During Step III, the structure of silica aerogel was completely destructed, while the density can reach to about 1600kg/m3.

Intermediate stages of surface state formation and collapse of topological protection to transport in Bi2Se3

Surface states consisting of helical Dirac fermions have been extensively studied in three-dimensional topological insulators. Yet, experiments to date have only investigated fully formed topological surface states (TSS) and it is not known whether preformed or partially formed surface states can exist or what properties they could potentially host. Here, by decorating thin films of Bi2Se3 with nanosized islands of the same material, we show for the first time that not only can surface states exist in various intermediate stages of formation but they exhibit unique properties not accessible in fully formed TSS. These include tunability of the Dirac cone mass, vertical migration of the surface state wave-function and the appearance of mid-gap Rashba-like states as exemplified by our theoretical model for decorated TIs. Our experiments show that an interplay of Rashba and Dirac fermions on the surface leads to an intriguing multi-channel weak anti-localization effect concomitant with an unprecedented tuning of the topological protection to transport. Our work offers a new route to engineer topological surface states involving Dirac–Rashba coupling by nano-scale decoration of TI thin films, at the same time shedding light on the real-space mechanism of surface state formation in general.

Experimental Study on Sinkholes: Soil–Groundwater Behaviors Under Varied Hydrogeological Conditions

Abstract Sinkholes have been one of the major geohazards in karst terrain and have resulted in loss of human life, as well as significant civil engineering infrastructure. Approximately 20 % of the United States is underlain by karst terrain formed from the dissolution of soluble rocks, and is susceptible to a sinkhole hazard. Particularly, Texas, Florida, Tennessee, Alabama, Missouri, Kentucky, and Pennsylvania are known as sinkhole states. Surprisingly, the understanding of sinkholes is still poor in geotechnical engineering. This paper presents and discusses a preliminary study on the mechanism of Florida's sinkholes that are triggered by groundwater flow. A physical soil–groundwater model was devised, and multiple tests were conducted under different hydrogeological conditions (e.g., with/without aquitard and overburden soil thickness). Groundwater at multiple locations was monitored during the sinkhole-simulation process so that integrated soil–groundwater behaviors could be investigated. It is found that groundwater responds before the surface collapse (showing a cone of depression); thus, a pattern change of groundwater flow can be used as input to pre-detect a sinkhole. In addition, having a clayey sand layer within sand shows a significant influence that includes a rapid change of groundwater flow in the sinkhole process and a larger surface sinkhole.

Application of Distributed Optical Fiber Sensing Technique in Monitoring the Ground Deformation

The monitoring of ground deformation is important for the prevention and control of geological disaster including land subsidence, ground fissure, surface collapse, and landslides. In this study, a distributed optical fiber sensing technique based on Brillouin Optical Time-Domain Analysis (BOTDA) was used to monitor the ground deformation. The principle behind the BOTDA is first introduced, and then laboratory calibration test and physical model test were carried out. Finally, BOTDA-based monitoring of ground fissure was carried out in a test site. Experimental results show that the distributed optical fiber can measure the soil strain during ground deformation process, and the strain curve responded to the soil compression and tension region clearly. During field test in Wuxi City, China, the ground fissures deformation area was monitored accurately and the trend of deformation can also be achieved to forecast and warn against the ground fissure hazards.

3Dスキャナによる切羽変位のリアルタイム検出

In mountain tunnel excavation work, numerous accidents have been reported due to face surface collapse. It is known that face surface displaces by a few centimeters just before the collapse. However, it is very difficult for workers to find such displacement visually. In this paper, we propose a new method for real-time detection of minute displacement of tunnel face surface using high-speed 3D laser scanner. Compared to the previous works, our method can capture the sudden displacement of the surface in real time without any preparation to the surface.