Physical Modeling of the Controlled Water-Flowing Fracture Development during Short-Wall Block Backfill Mining

Short-wall block backfill mining (SBBM) technology is an effective method to solve the environmental problems in the mining process. Based on the technical characteristics of SBBM technology and the physical similarity criterion, the physical similarity models for comparing the control effects of water-flowing fracture (WFF) development using short-wall block cave mining (SBCM) and SBBM were established, and the deformation and the WFF development of overlying strata above gob were monitored. The test results determined that the composite materials of 5 mm thick pearl sponge+5 mm thick sponge+10 mm thick paper+6 mm thick board were adopted as the similar backfill materials by comparing the stress-strain curves between the similar backfill materials and the original gangue sample. When the backfilling body was filled into the gob, it would be the permanent bearing body, which bore the load of the overlying strata accompanied with the protective coal pillar. At the same time, the backfilling body also filled the collapse space of overlying strata, which was equivalent to reduce the mining height, and effectively reduced the subsidence and failure height of the overlying strata. Compared with SBCM, the test results showed that the maximum vertical deformation, the height of water-flowing fractured zone, and activity range of overlying strata using SBBM were reduced by 91.4%, 82.5%, and 64.9%, respectively. SBBM had a significant control effect on strata damage and WFF development, which could realize the purpose of water resource protection in coal mines.

Field Measurement and Mechanical Analysis of Height of the Water Flowing Fracture Zone in Short-Wall Block Backfill Mining beneath the Aquifer: A Case Study in China

Short-wall block filling mining (SBBM) technology has become an effective way to recover coal resources beneath the aquifer, which are unsuitable, or cannot be used by long-wall mining, such as corner coal pillars, industrial square pillars, and irregular coal blocks as well as the coal beneath buildings, railways, and water bodies. The SBBM method can not only enhance the recovery ratio but also provide a solution for the environment problems associated with gangues on the surface. However, whether the height of water flowing fractures will reach to the aquifer to cause water loss during SBBM has always been a key problem. Therefore, based on the theory of elastic foundation beam and SBBM characteristics, a mechanical model for calculating the height of a water flowing fracture zone in the overlying strata of SBBM was established, and this model calculated that the height of the water flowing fracture zone was 27.0 m in the experimental working face, and the height of the water flowing fracture zone was measured as 26.8 m according to washing fluid loss in the hole, core damage analysis, and drilling TV imaging detection. The comparison results demonstrated that the calculated value almost fit well with the field-measured data, validating the accuracy of the proposed mechanical model, while the predicted value (48.7 m) in the Regulations of coal mining under building, railways and water-bodies deviates greatly from the measured results. This reveals that the prediction formula in Regulations is not effective in predicting the height of the water flowing fracture zone in SBBM. The present research results are of great significance to further enhancing the recovery ratio of coal resources and improving the water-preserved mining theory.

Assessment of a Lateral Nasal Wall Block Technique for Endoscopic Sinus Surgery Under Local Anesthesia

Introduction With increasingly limited operative resources and patient desires for minimally invasive procedures, there is a trend toward local endoscopic procedures being performed in the outpatient clinic setting. However, there remain limited data supporting a technique to adequately anesthetize the lateral nasal wall and provide patient comfort during these procedures. The objective of this study is to assess the efficacy of a novel lateral nasal wall block for use in office-based endoscopic sinus surgery. Methods A prospective cohort study assessing consecutive patients undergoing office-based endoscopic sinus surgery using our described lateral nasal wall block anesthesia technique. Procedural patient comfort was assessed using the Iowa Satisfaction with Anesthesia Scale (ISAS), completed by participants immediately following an office-based endoscopic procedure and prior to discharge from clinic. Postoperative analgesic use was assessed at the first postoperative visit. Results Thirty-five consecutive patients undergoing office-based outpatient endoscopic sinus surgery for chronic rhinosinusitis (with and without polyps) were assessed. The mean ISAS score was 2.83 (95% confidence interval: [2.69, 2.97]). All participants (100%) agree or strongly agree that they were satisfied with their anesthesia care and would want the same anesthetic again. No participant required narcotic analgesia, and 80% used no oral analgesia following the procedure. Conclusions Recent advances in office-based endonasal surgical procedures must be accompanied by the assessment and validation of local anesthetic techniques. The described novel lateral nasal wall block is well tolerated, provides patient satisfaction, and allows for limited use of postprocedure oral analgesics.

Randomised Comparison of Three Types of Continuous Anterior Abdominal Wall Block after Midline Laparotomy for Gynaecological Oncology Surgery

Effective analgesia after midline laparotomy surgery is essential for enhanced recovery programs. We compared three types of continuous abdominal wall block for analgesia after midline laparotomy for gynaecological oncology surgery. We conducted a single-centre, double-blind randomised controlled trial. Ninety-four patients were randomised into three groups to receive two days of programmed intermittent boluses of ropivacaine (18 ml 0.5% ropivacaine every four hours) via either a transversus abdominis plane (TAP) catheter, posterior rectus sheath (PRS) catheter, or a subcutaneous (SC) catheter. All groups received patient-controlled analgesia with morphine, and regular paracetamol and non-steroidal anti-inflammatory medication. Measured outcomes included analgesic and antiemetic usage and visual analog scores for pain, nausea, vomiting, and satisfaction. Eighty-eight patients were analysed (29 SC, 29 PRS and 30 TAP). No differences in the primary outcome were found (median milligrams morphine usage on day two SC 28, PRS 25, TAP 21, P=0.371). There were differences in secondary outcomes. Compared with the SC group, the TAP group required less morphine in recovery (0 mg versus 6 mg, P=0.01) and reported less severe pain on day one (visual analog scores 36.3 mm versus 55 mm, P=0.04). The TAP group used fewer doses of tropisetron on day one compared with the PRS group (8 versus 21, P=0.016). Programmed intermittent boluses of ropivacaine delivered via PRS, TAP and SC catheters can be provided safely to patients undergoing midline laparotomy surgery. Initially TAP catheters appear superior, reducing early opioid and antiemetic requirements and severe pain, but these advantages are lost by day two.